90hp 2stroke Yammy issue

[Matthew Thompson]

Hi all,

After some advice here, recently had my motor service, 90hp 2 stroke yammy 2004 model with 300 hours on the clock.

It was running fine but not idling great, so I got it serviced, Carby cleaned, new impeller, fuel filter etc.

On its first run it ran like a dream, done about 50kms all up, full noise and some trolling, couldn't be happier.

Then this morning went to take it out front, got 12kms from the boat ramp and lost power.

Limped back home, couldn't get it over 28 revs, got home checked the fuel lines filter seals etc, thought it might be sucking air some where but all looked good.

Started it up with the muffs on, started running sweet got the revs up all looked good then the alarm came on and it dropped back down in revs, water out of the tell tail was boiling hot.

It sounds like an over heating issue maybe. What should I check next? Thermostat maybe?

Any help appreciated.

Thanks lads

[Matthew Thompson]

Just put a new Thermostat in, didn't make a different, alarm still came on and lost revs.

[Si]

Hi all,

After some advice here, recently had my motor service, 90hp 2 stroke yammy 2004 model with 300 hours on the clock.

It was running fine but not idling great, so I got it serviced, Carby cleaned, new impeller, fuel filter etc.

On its first run it ran like a dream, done about 50kms all up, full noise and some trolling, couldn't be happier.

Then this morning went to take it out front, got 12kms from the boat ramp and lost power.

Limped back home, couldn't get it over 28 revs, got home checked the fuel lines filter seals etc, thought it might be sucking air some where but all looked good.

Started it up with the muffs on, started running sweet got the revs up all looked good then the alarm came on and it dropped back down in revs, water out of the tell tail was boiling hot.

It sounds like an over heating issue maybe. What should I check next? Thermostat maybe?

Any help appreciated.

Thanks lads

Did you flush the engine after the first run following the service and what did you use for flushing, ear muffs? Did you have a good seal? What condition is the impeller when you replaced the thermostat?

[Crunchy]

Did you check the PCV when replacing the thermostat? Its the spring loaded plastic cross thingy and it should be free to move in and out and not stuck.

I had the same overheating problem a little while ago which I rectified by either:
1) Cleaning up the PCV and thermostat or
2) Removing the kink I had in the hose

I'm not sure which of these fixed the issue but it got fixed, I think it was the kink. Enough water flowed so that the telltale was working but perhaps not enough to cool the motor for a long period of idle time.

Perhaps check the right plugs put in during the service. BR8HS10's from memory.

[FNQCairns]

How was the poppet when you put the thermostat in? and did you do it all that fast?

My parts to service my 90 yam 2st turned up today....and within was a new thermostat and a new poppet/spring etc....I always twin them.

But as always with these things if something has gone wrong so few hours from a service....first ensure it was not the service that caused it....9 times out of 10 it will be someting service related one way or another.

What do your plugs look like as a matter of coarse?...I would double check the water pump...it's all so basic.......lack of water only at speed = thermostat and /or poppets...lack of water everywhere = plastic bag/other major blockage........lack of water only slow or still = water pump or something associated with it somehow.

[Matthew Thompson]

Did you flush the engine after the first run following the service and what did you use for flushing, ear muffs? Did you have a good seal? What condition is the impeller when you replaced the thermostat?
Yeah mate I flushed as I always do with the same muffs I have used before the service with the same hose etc, I am not to sure how to check the impeller but will jump on google now and have a look. Thanks for your help.

[Matthew Thompson]

Yeah mate that PCV thing is spring loaded and seems to be in fine working order, what hose did you have kink in?

Yeah my tell tail is running fine I will go check what spark plugs they put in now.

Thanks mate

[Matthew Thompson]

Will go check for blockages now thanks.

Bought a couple of brand new thermostats just the other day for the other motor we have here which is having similar issues which we thought we had fixed, just took that out and its cracked the sh!ts to, two boats in one week both with issues, bang smack in the middle of my holidays! Typical

[Fed]

I know sfa about yamahas.

Is it pumping oil?
Might be worth hooking a pre-mix tank to it.

[Matthew Thompson]

Plugs are BR8HS10's

[Matthew Thompson]

The oil level seem to have dropped in the mixer since I topped it up yesterday, done about 25kms this morning, any way you can by pass it though and see it the alarm goes off?

[Fed]

Hook a pre-mix 50:1 tank to it.

Do yamahas have a 'no oil' alarm or only an alarm for oil level in the oil bottle?

[Malcolm W]

As above, do all the easy stuff first. It sounds like a genuine overheat if it takes time for the alarm to come on. One way to make sure is to use a heat gun to check the heat, the head should be 50-60°C. The alarm for the 90 goes off at 84-90°C.

Having gone through this with my 115 overheating and doing plugs, thermostats, poppet and water pump, it turned out to be partially blocked galleries. I took the heads off and found scale and silicone type gunk blocking the galleries. Scraped everything clean put new gaskets on and she's all good again. I was using Macs to flush with, but have stopped as I believe it's possible some of the residue was from that.

Jump on to YouTube for a look at how to remove the leg and inspect the impeller. Also if you can use a bucket instead of muffs, you will get better pressure at higher revs.

[Fed]

Yes don't let me distract you too much, as I said I know sfa about yamahas.

My concern was the drop in rpm but they may well have something that limits the rpm in overheat conditions.

Times like this the genuine manual is your best friend.

[Malcolm W]

No, good call on the oil, I didn't think about that as my 115 is pre-mix. The low oil and overheat will both reduce RPM (have the Selocs manual in front of me). Borrow a heat gun for problem solving and move on to the oil if overheating is not the issue.

[Crunchy]

Yeah mate that PCV thing is spring loaded and seems to be in fine working order, what hose did you have kink in?

Yeah my tell tail is running fine I will go check what spark plugs they put in now.

Thanks mate

Kink was in the garden hose:-X

Lets have a review so far:

1) It is an overheat issue. The telltale water is boiling hot and it shouldn't be. There is nothing to be gained by using a heat gun to check if its hot, you already know it is. If you can hardly hold your hand on the head (Once the alarm goes off) for about for 10 - 20 seconds then its too hot.
2) It ain't the oil. The oil level went down so the mixer is doing what it should - don't waste your time looking at this. Do you have the standard gauges that come with this motor? There are separate temp and oil indicators alarms that flash when the sound alarm goes off depending on which alarm it is, have a look to satisfy yourself.
3) Thermostat, plugs and PCV all checked and OK.

Your focus therefore should be on the impeller / water pump or a blockage in the system. There are a couple of other things it could be - including something to do with the carb set up, I will check my manual tonight and post what Yamaha says to look at with an O/heat alarm.

We'll get there mate.

[Horse]

If the tell tail is running strongly I would be considering blockages. If they still have flow but have mineral deposits building up then you could try running in a bin of water with a heap of vinegar in it. Its surprising what it cleans out. Check out "The Hull Truth" for details

[Matthew Thompson]

Thanks for all your help, I pulled the impeller apart, checked it etc put it all back together, seems to be no blockages in there, can't really say I knew what I was looking at though.

I took the thermostat and PCV thingy out and run it to make sure water was getting pumped through there, seemed to be working all good.

Put it all back together and gave her another crack, and she ran fine, no alarms.

So will put it in the water and go get some livies and hopefully get out and chase some fingermark.

3rd time lucky for the day I hope.

Thanks for all your help wouldn't have had any idea where to start with out some guidance. Think I should be able to change the impeller by myself next time too which is a bonus to have learnt some thing new.

Cheers
Matt

[FNQCairns]

Thanks for all your help, I pulled the impeller apart, checked it etc put it all back together, seems to be no blockages in there, can't really say I knew what I was looking at though.

I took the thermostat and PCV thingy out and run it to make sure water was getting pumped through there, seemed to be working all good.

Put it all back together and gave her another crack, and she ran fine, no alarms.

So will put it in the water and go get some livies and hopefully get out and chase some fingermark.

3rd time lucky for the day I hope.

Thanks for all your help wouldn't have had any idea where to start with out some guidance. Think I should be able to change the impeller by myself next time too which is a bonus to have learnt some thing new.

Cheers
Matt

Good stuff thisis where it all starts...at the start for good reasons.

Just to further the Vinegar reference above by the guru Fed....some people and I dunno who that might be :) and I would never advocate it ever...stupid thing to do in this day and age of people all but considered 5 years old in all aspects of their simple abilitys without a piece of paper to flash.....some people have been known to add some swimming pool hydrochloric acid to their flush as a weak solution......HCL (did I get that right) simply loves loves carbonates....eats them alive, fizzes them away to nothing much but co2.


Sticky thermostat? sometimes just a sticky poppet if it happens at speed.

[Fed]

Huh?
I don't even flush half the time let alone add vinegar.

[FNQCairns]

Sorry Fed I thought you mentioned Vinegar above somewhere...must have been another post by someone on this thread or elsewhere, I should have re-read not been so lazy.

[Spaniard_King]

Check Impellor housing, probly melted behind the cup sucking in air

[Justin Rossiter]

In the Hull Truth article the guy uses approx. 15l of vinegar (4 Gallons) that is a lot of vinegar !!

http://www.thehulltruth.com/boating-how-s-kerno-memorial-forum/368827-how-cleaning-your-cooling-system-vinegar.html

[Malcolm W]

Tried the mythbusters thing after reading about vinegar, when I took both heads off my 115 Yamaha. Put one head in a tray of vinegar for 20-30 min to see if it would dissolve the scale build up as it's a mild acid. It certainly does work in disolving the softer outer scale, but the harder build up had to be scraped off.

[Matthew Thompson]

I am back and its didn't go as planned! Engine still loosing power at 27 revs, runs fine until its in the water and I put the throttle down and it get the revs up to 27ish then has no more punch.

It still seem to be pumping water fine, the water from the tell tail is warm and its pumping at constant pressure etc I will double check the impeller housing, if it is sucking air would that mean it loses power? I remember looking at it this arvo when I pulled it apart thinking it didn't look to be sealing 100% but I have never pulled it apart before so not sure.

A mate suggested checking the plugs, they were only replaced a few weeks back would this limit the power if one was buggered?

What's your thoughts on it sucking in air in the fuel line? I am going to hook up a tote tank tomorrow and see if that will help as it should by pass most of the fuel line, but it would be weird that it started 12km from the boat ramp as full noise.....

going to be a sleepless night, and to make matters worse the sail fish have just started to turn up in numbers here in the gulf.....

[davo]

I know a bloke who had similar issues with his 2 stroke 70HP Yammy. It was scale build up. He used barnacle buster. It is specifically for the job. Another bloke I work with used to work in the marine industry and used lemon juice. I used salt x on an 8HP Suzuki and it bubbled and carried on but cleaned the blockage.

[mutineer]

Primer bulb stuffed , or fuel line denigrating inside , junk in pick up in tank , filter fuel blocked .

[dnej]

Did you read the post by Garry. he is the expert on such matters.
David

[Crunchy]

Did the overheat alarm go off again?

[Matthew Thompson]

Nah no over heat alarm any more. Any the water out of the tell tail seems to be fine. Will try the tote tank and a new Bulb today when I get a chance. And will let you know how I go.

Thanks again.

[Si]

Peter Staig's Cooktown Marine


(07) 4069 6111
1 Boundary St

CooktownQLD4895

[Matthew Thompson]

Don't live in Cooktown any more mate.

[Moonlighter]

Don't live in Cooktown any more mate.

Time to update the details in your avatar, in that case!

One crook plug can certainly curtail your revs and will typically happen under load, such as when you are trying to push her up onto the plane. Engine would be shuddering and not smooth like usual.

Pull them out and have a look at each one, if one is crook it will be black most likely.

[Matthew Thompson]

Cleaned the plugs ran the engine off a tote tank, hasn't made a difference still can't get it up over 27revs. Checked the fuel filter. Running out of ideas

[Gon Fishun]

I don't know anything about the Yammies but do they have 3 carbies? and are they all working, as in fuel bowls have fuel, throttle plates all opening and synchronised, no blockages to maybe 1 carby?? or 2 ?? You did say they had been cleaned, was that removed and stripped. Might have dislodged some muck and it is floating around inside the carby?
Have you done a comp test?

[dogsbody]

Is something impeding throttles full movement? Had it happen on my motor when a loose linkage was hitting other gizmo not allowing full throttle.


Dave

[feral cat]

Ok first things first.no alarm means oil tank is fine and its not a heat issue.
Sounds like blocked main jet.
Here's something to try.Start engine and leave it idling.Get a pair of insulated plyers and pull the top spark plug cap off, what your listning for is a change in idle.Then put back on and do same for others.if you hear change in idle for each plug cap you pull off means your idle jets are fine.(which i suspect would be considering you cant get past 2700rpm)
Drop the drain screw off each carby and blow air in with compressor as this can blow your main jets clear.Dont be scared to give em some either.Pull your air mixture screws out and do the same.(air muxture screws are all the way in then 1 and half full turns out.)Blow air in top holes whilst covering drain screw hole with finger as well.Then take for a run.If it still does it you might have to pull carbies off and clean.Also those 90's need a 10 micron fuel filter as well as the jets are fine.
Interested to see how you go.
If its getting hot the alarm will sound and goes into limp mode untill alarm stops then you can go again untill alarm sounds again.
Also check your oil drive.leave motor off and in gear full throttle.on the port side of motor under the oil tank is a worm drive with a connector arm going to carbies.make sure you its hitting its stopper at full throttle.

[feral cat]

Was there an alarm originally or not untill at home with muffs on.

[cormorant]

dumb one - are the plug leads on the correct cylinders? Won't be the first motor where the leads are long enough to be accidentally put on the wrong plug.

[Matthew Thompson]

I got the boat serviced three weeks ago which included a carby clean, new filters, impeller etc, also a new throttle cable. My first run after the sevice I did a 50km run with no drama engine ran smooth! Yesterday I was 12km from the boat ramp going almost full noise and the engine missed a bit so I backed off and couldn't get the boat back up past 27revs. I got home flushed the engine and the alarm came on, the water out of the tell tail was red hot.

[Matthew Thompson]

To try and find/fix the problem I have done the following:Replaced the thermostat and checked the Pcv thing they seem fine.
I ran water through the engine and water came out of where the thermostat sits.
I took the impeller apart and nothing was stuck in there, it seemed fine, but I don't know much about them...
I have run a new fuel tank on the engine and it didn't help.
I pulled the plugs out cleaned them and put them back in. I also pulled one off at a time and listened to the engine noise, they all made the engine run differently.
I have checked the carby openings and they all seem to be clean and working fine.


The boat runs fine when on the muffs and I can get it up past 27revs...


So that's where I am at so far taking the day off to go hunting today but if any one has more ideas I'll try then tomorrow thanks all for your help!

[Gon Fishun]

Nah no over heat alarm any more. Any the water out of the tell tail seems to be fine. Will try the tote tank and a new Bulb today when I get a chance. And will let you know how I go.

Thanks again.

It sounds you have, or had 2 problems. 1 was overheating which you have fixed and the other is the tuning. You need to look at that side as suggested by the other guys.

[Gon Fishun]

To try and find/fix the problem I have done the following:Replaced the thermostat and checked the Pcv thing they seem fine.
I ran water through the engine and water came out of where the thermostat sits.
I took the impeller apart and nothing was stuck in there, it seemed fine, but I don't know much about them...
I have run a new fuel tank on the engine and it didn't help.
I pulled the plugs out cleaned them and put them back in. I also pulled one off at a time and listened to the engine noise, they all made the engine run differently.
I have checked the carby openings and they all seem to be clean and working fine.


The boat runs fine when on the muffs and I can get it up past 27revs...


So that's where I am at so far taking the day off to go hunting today but if any one has more ideas I'll try then tomorrow thanks all for your help!

Very possible it will rev higher when not under load. When it is loaded ( under way ) that's when the problem arises. If it's not running rough, like missing at higher revs I would be inclined to look at fuel starvation.

FWIW. I have a V4 twin carby Evinrude 2 st. It had sat for a number of years and was gummed up. But to cut a long story short, out on the water under way it decided to slow and wouldn't rev over 2500 or thereabouts. Travelled slowly ok, no vibration. What happened was a piece of rotted fuel hose got to the needle and seat and restricted the fuel flow to 1 carby. Cleaned out, back to full noise.

[bigpat]

I'm no expert...
Seems overheating issue is sorted, so it might be either spark or fuel.
As for fuel, even though carbs were cleaned, I'd follow the advice given to give them a blow out, and try the spark removal test at idle.

Seems you've changed everything else.

As a more out there suggestion , does anyone think it could be a damaged reed valve?

[feral cat]

G'day again mate, looking at carby openings will not do anything as you have to pull carby's off to get bottom fuel bowls off to access main jets. A good blow out as I suggested might free the deposit from main jet and give it some to. There triple carby's and it only takes ones to block and you are then limited to 2600 to 2800rpm. Yammy v4's are the same but quad carby's. When you take the drain screw out of bowls look for a bit of crap to come out as well.
For piece of mind might just be easier to pull carby's off and clean then that's that eliminated.

[Matthew Thompson]

Thanks I'll pull the carbys apart this arvo and see if there is any thing in there, are the carbys easy to take apart and put back together? Don't want to make it worse

[Fed]

As others have already said, I'd give it a compression test first.

[FNQCairns]

Yeah really easy to take apart....just be sure not to readjust any of the spark timing side....there will be a rod running from the throttle cam back parallel to the ground to a big vertical arm that moves the under-flywheel timing plate....make sure this parallel rod doesn't get changed in it's length in any way.

Also play with the linkages a little bit ot see the relationship of the throttle cam at idle....you will need to bring it all back to these exact positions again one way or another....assuming they where good in the first place.

[Matthew Thompson]

Firstly thanks for all of the responses, I ticked a lot of the possible causes off!

I had the outboard mechanic down from Weipa this morning and he found the jet in the carby were blocked. So I got a bad batch of fuel and am going to have to drain my fuel tank.

I watched him do it so I could learn how to clean the Carbys my self in future, pretty interesting and not that hard to do.

Learnt a lot, so cheers to every one for taking the time to help.

Regards
Matt

[cormorant]

Now to get suitable filters sorted if you haven't so it doesn't make it to the carby next time and even use a filter funnel to ensure no water or grit gets through.

The bits blocking your carby may well have come from inside your fuel lines if they are detiorating so that may be worth looking at as well and replacing any suspect fuel lines.

[Matthew Thompson]

buying a couple of inline filters today mate cheers

[cormorant]

check the filter has a suitable flow rate and much finer than your jet size or they might be a lot more trouble than they are worth and also is designed for the correct hose size.. Need to be fitted well as there is a vacume in the hose from the motors fuel pump drawing the fuel from they tank so ensure any hose fittings are well clamped.

[Matthew Thompson]

Cheers mate will do my best

[Crunchy]

I think the Racor water separating filters are quite a good brand - its what I have always used and not a single fuel issue in 5 years.

[Fed]

The standard under cowl filter would stop anything remotely large enough to block a jet.
How does stuff get into carbies, either a human put it there by being slack, the hoses after the filter are falling apart or there was some water inside the fuel bowl allowing a bit of corrosion.

That's my 2 bobs worth.

[cormorant]

you mean the mesh sediment one under the cowl?? or the even coarser one at the fuel pump screen?

yep still no paper in them I think but I could be wrong. I like a paper one to stop some the gum , contaminants and stuff that can form in stored fuel.

http://www.ebay.com.au/itm/NEW-YAMAHA-OUTBOARD-FUEL-FILTER-ASSEMBLY-SUITS-9-9-TO-90-HP-/190894270122?nma=true&si=bzbVws9PVPSyCw4okHncQ3nsTIA%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

[gruntahunta]

Compression test mate....I know it's not what you want to hear if it is down on compression, it can run well on the muffs but not on the water....perhaps the initial overheating has done damage and now causing this problem

I would do a compression test first.

[Fed]

Both mate but I actually think the fuel pump screen is a leftover from bygone Mercury days when they didn't even fit a separate inline filter.
(Merc/Yam affiliation)

[Fed]

This whole thread is a headspin, boiling telltale water that magically fixed itself and crap in the carbies that magically appeared, I dunno, maybe I missed something.

[feral cat]

Firstly thanks for all of the responses, I ticked a lot of the possible causes off!

I had the outboard mechanic down from Weipa this morning and he found the jet in the carby were blocked. So I got a bad batch of fuel and am going to have to drain my fuel tank.

I watched him do it so I could learn how to clean the Carbys my self in future, pretty interesting and not that hard to do.

Learnt a lot, so cheers to every one for taking the time to help.

Regards
Matt

Matt i was wondering how got on.Glad you had a win.
I've done 1500 plus hrs with twin yammy 90's and i found the best filters for them was racor water seperating fuel filters which is 10 micron.
Keep an eye on clear bowl at the bottom and drain regurlary and change filters every 100hrs.
cheers and good luck.

[Matthew Thompson]

Cheers mate ill get some of those