help please old motor trouble.

[Navi]

hello out there,

I am having motor trouble, I took the boat out yesterday and instead of doing 23 mph i was doing 16, the motor sounded like the rev's were dropping off then back up again, but still not getting full rev's any way, I had just got new fuel so didn't think it could be that, it's an 1977 mariner 40E 40 hp, i was told that by ajusting the air / fuel screw would fix this,I was told to do the screw right up then turn it 3 1/2 turns, tried it but stalled after idling for a couple of min's.
I have taken a couple of photo's of the carby,
the top screw is the idle screw so I take it,
the the other has to be fuel / air,
am I right ?
if so is it right to turn it 3 1/2 turns ?

if any one has any idea's I would be grate full ( besides buying a newer motor, just brought house, no money left )

cheers chris 8-)

[Angla]

Did it idle well before the adjustments to the carby?

I would suggest you look at the sparkplug leads for a breakdown in the insulation from rubbing against the cowling or something. The funny thing about high tension leads is that they break down at higher revs and generally not at low revs.

Chris

[Roughasguts]

Ooops next time you feel the need to adjust them count how many turns to get them lightly seated first, then you have a starting point with out the manual.

Just guessing here the little one is the idle air/mixture screw the big one the High speed jet, Check to see if the big one is screwed in tight thinking the high speed mixture should be fixed not adjustably.

But anyway that amount of screwed out 3.5 seems way to much, maybe 1.25- 1.75 screwed out from lightly seated. But I don't know your motor specs so hopfully someone here can give you the corect specs.

If you do have the high speed adjustable mixture make sure it is corect! as leaning out your motor will put a hole in your piston, so a trip to the outbord tech would be good insurance, against further damage.

Sorry I'm not much help here.

You should try the simple fixes first, replace plugs, drain and flush float bowl, clean fuel filters, check fuel line for air leaks try the suction test on all fittings.

If all else fails then maybe adjust mixtures, they don't just work there way out.

[Navi]

[quote=Roughasguts;591471]

You should try the simple fixes first, replace plugs, drain and flush float bowl, clean fuel filters, check fuel line for air leaks try the suction test on all fittings.

quote]

done all the above, I haven't adjusted any thing yet,
cheers chris

[FNQCairns]

I have no good knowledge of your motor, but exclusivly in my experience there is no medium or high speed adjustable screws, the only screw that is adjustable for mixture is the low circuit jet screw. If you get this wrong it will not idle idle where you dont want it too. The 3 circuits are independant but work together as RPM increases, good design actually so people cannot twiddle a high speed or mid range jet by screw and blow the engine up in short order.
You cannot fix any problem above say 1100rpm with the idle circuit screw, your problem is elsewhere -fuel/elect problem/overheat etc.

Also these are not like other engines a person cannot change the idle speed manualy (apart from the idle circuit screw which is a mixture adj and does not impact the mechanical workings of the carb).
The carb is set and forget in it's mechanical workings and idle speed is a function of idle timeing and idle mixture, adjusting the butterfly further does nothing but put it ALL out of spec. A totally different animal to a 4 stroke carbs etc.

Once you get the engine idleing nice the idle screw is in the correct spot, they are slow to respond so turn it a bit then wait 10sec then repeat or you will overshoot the sweet spot each time.

cheers fnq

[blaze]

The first thing I would suppect is air leak in the fuel line
cheers
blaze

[Hamish73]

the idle speed screw(on the trottle arm) and the idle mixture screw (on the carby body) will make no difference to full throttle operation. You problem is elsewhere. Possibly ignition related as mentioned earlier.

[finga]

If I remember right those motors have points.
Could be dirty points or they could have moved as well.
A crook ground connection or crook connect could also be a culprit but I'd be looking at the fuel connections before delving deeper
IMO don't touch the mixture screw. Things that happen all of a sudden usually mean something on the fritz. Adjustment is going to upset the applecart a bit more.

[Kleyny]

What did it run like at the rest of the rev ranges??? (idle,mid, mid-high, from idle to flat out "giving it a fist full")
Answering these quick question may help myself and others give us a better/ bigger picture on what maybe going on.

Neil

[Roughasguts]

You know 1977 is a pretty old motor, wouldn't mind betting the fuel pump ain't cutting it anymore. Try pumping the fuel bulb when your out next time see if that makes a differance.

[Navi]

Thank's guys, it idles okay when you first start then after giving it the throttle for say half hour and pulling it back to idle it will idle rough then say after 2-3 mins idle it will stall. mid- mid high seems to run rough and flat out is the same, it sounds like it's not getting all the rev's when flat out,I took the conectors off the fuel line and conected it straight on to the fittings but still no good.

cheers chris

[searchinthebay]

Ok i have a question for you that might sound simple but did you loosen off the fuel tank air screw on the cap. It could be that if you haven't there is a vaccum forming in the tank and stopping the fuel flow to the motor. I know this cause i forgot to do this one day. Took me ages to work it out. Wasn't until the next day that i found it. Bloody idiot huh

[Kleyny]

Does it blow lots of smoke???

[Navi]

Ok i have a question for you that might sound simple but did you loosen off the fuel tank air screw on the cap. It could be that if you haven't there is a vaccum forming in the tank and stopping the fuel flow to the motor. I know this cause i forgot to do this one day. Took me ages to work it out. Wasn't until the next day that i found it. Bloody idiot huh

yep first thing I do when I get in the boat.

cheers chris

[searchinthebay]

me too now

[yalta]

do a compression test on it could be getting tired.

[Kleyny]

do a compression test on it could be getting tired.

just a out curiosity what made you come up with this as a possibility?

[Roughasguts]

Hmmm, reading the symptoms again and if it ain't fuel, or spark.
There is the slightest possibility she's getting way to hot, the oil ain't doing it's job, and she's seizing up. You have got good oil in her ? Marine grade.

Take the plugs out next time she stops, and turn her over by hand, compare that to when she's cold, if she's stiff to turn over don't sound good.

Might not hurt to pull the plugs out and fill the pots with carby clean, that should remove some carbon build up.
Start her up straight away after though, to lube the motor up again.

[Kleyny]

Roughas i was thinking on the lines of junk in the carby or even the choke stuck on.
But your latest theory fits. I hope its not for Navi sake.

neil

[Roughasguts]

Yeah it does fit Honky Dory, but it's only a slight chance.
More likely a coil dying out when she gets hot, and comming good when cold.
Is that a 3 cyl model or 2 if she's a 3 cyl, very likely to be a dud coil.

Many a johno have these symptoms, and it's just a matter of finding which coil and replacing it.

[armoz]

do your self a favour, call a mechanic.....
were are you located? This might be a simple problem and they coould suggest something over the ph. If ur anywhere near the sunny coast I know a mobile guy that is good and charges a fair price (happy to teach you as he goes as well)

[Navi]

nope not to much smoke may be a little on first start when cold.
2 cyl motor, I'll try the carby clean, and I'm looking in to get a new coil, if then still problem then get a mobile man around, I'm on the south brisbane side so if you guys know of any good ones please let me know.

cheers chris

[Kleyny]

Navi does the engine start once it has stalled straight away?
Or do you have to let it cool before it will start?
How hot is the water coming out of the tell tail?

Sorry about all the questions just trying to lead you in the right direction.

Neil

[Kleyny]

On the mechanic side of things i cant help you on the south side or even the northside for that matter. i do know one on the sunny coast(probably the same one as armoz).
but i can imagine what they would say (i can look at it but its not worth fixing. heres a few second handies I've got for sale. I'll have trouble finding parts etc. etc.etc.etc.)

[Roughasguts]

Navi that almost blows the bad coil theory if she's a 2 cyl, can't imagine her getting 16mph on one lung, but possible if a 3 cyl running on only 2 cylinders.

[Kleyny]

Navi that almost blows the bad coil theory if she's a 2 cyl, can't imagine her getting 16mph on one lung, but possible if a 3 cyl running on only 2 cylinders.

the coil could only be on the way out heating up and give poor spark (not no spark).

Just thinking out loud

[armoz]

I don't know much about engines, but did you checj the heads? they might be full of salt build up or something similar.. as for the mechanic, mines on the sunny coast - not sure if he travels to sth brisbane but he might give you some answers over the phone ( he doesn't have 2nd handies to sell - he's an old scholl tinker, starts at 1 end and works his way through till he solves the problem. His name is Howie 0403 404 076 he's a good guy so might be able to help. Tell him u know scotty at Pelican waters!

[Navi]

after first started it will start straight away first pull, tried to compreshion test not sure if I'm doing it right but I screwed it in and pulled it like I was starting the motor just one pull the lenght of the cord top head 110 psi bottom 105.

cheers chris

[Kleyny]

thats not to bad for an oldy mate.

If it was mine I'd be happy with those readings.

did you check to ensure the choke is all the way off ( inside the carby). just something to do to rule out another variable.

neil

[Navi]

i haven't checked the choke yet but I will tomorrow putting in new plugs also got another coil, and will do the carby cleaner down the ports, question with the carby cleaner done do I have to add something to lube the cylinder more or will the oil in the fuel mix be enough ?? ( I know some of you proberly think what a stupid question but I want to make sure)
cheers chris

p.s getting hold of a work shop manual for the motor tomorrow.

[Kleyny]

the oil in the fuel should be enough. its enough during normal operation so it will be enough after the carby clean trick. (the carby clean will burn off after the first couple of fires.)

neil

[Navi]

Honky Dory.... Thanks Mate,

Cheers Chris

[Navi]

well put carby clean in to ports gave it a couple of pull's with out the plugs in, then put new plugs in it put another coil in it, and gave it a basic tune thank's to logan city library for the photo copys of the manual, it seems to idle alot smoother but wont know about full rev's till next weekend...

cheers to every body who helped out, I'll let you know what happens next monday. Also did a compression test after the carby clean and got 120 psi top cyl and 115 bottom cyl.


cheers Chris

[Roughasguts]

Sounds good so far Navi, give her a good hard flogging for several minutes. It wouldn't hurt to do it again, the carby clean trick down the spark plug holes that is, while the boat is already out.

Those comps are sounding a bit better also.

[20pounder]

" had just got new fuel so didn't think it could be that"
New fuel caused me a lot of headaches. Always think of the last thing you did before things went wrong.
Sorry I didn't put the quote in a box.

[Roughasguts]

New fuel can cause lots of problems.
Filled my car 3 days ago after a huge down pour.
Now it runs like sh!t up hill. Took me a while to work out I got maybe a few litres of water in me tank.

But pretty happy really petrols cheaper than bottled water, now days.

[Navi]

yahooooo misses has given permission to take the boat for a run down the river today, i'll do the carby clean again Then I'll give it heaps, just hoping I can get it to go flat out, cause the library would only copy 10 pages of the work shop manual so I took the tune up part, *LOL*

cheers chris

[Kleyny]

let us know how he goes mate

good luck.

[finga]

Hey Chris let me know which other bits you need in the manual and I'll go and get 10 pages. I have the cooks card as well ;)
Good luck today matey :)

[Roughasguts]

Navi getting worried about you. Did you get back from the test run ? Should we send food and Beer ?

[Kleyny]

Navi getting worried about you. Did you get back from the test run ? Should we send food and Beer ?
I'll be in that type of search PARTY

[Navi]

Sorry guys didn't get to do test run as my youngest boy is sick, been up the hospital with him instead, hope to give it a run before thursday as I'm heading up to hervey bay with it,.you can still send the beer over but I have plenty of food thank's.


cheers Chris

[Roughasguts]

Hope the young fell'a is alright Navi, nothing worse than a sick child.
Yeah my kids come first, some where after the lawn mower comes the missus.

Which reminds me better go and take her out for a spin, before the kids get home.

And mow what's left of me grass.

[Kleyny]

Navi,
How is your boy going?
Have you had a chance to test the motor yet??
Keen to find out how it went.

[finga]

Mate, He's away on holidays I think atm.
He put it in a test tank and it revs and and the idle is nice and smooth.
Apparently a lot of the timing settings were out as well.
Chris will have more to say when he returns I'd say.

[Navi]

Hey hoo, I'm Back well for a couple of days any way then off to south straddie for a week, the motor ran smooth a lot smoother then before but I am not getting full rev's , is there any way of adjusting it to rev higher? with out upsetting idle.
we picked the wrong day to go out up there windy and rough as. had fun caught a few fish hooked up on some thing that snapped 30 lb fire line.
cheers chris8-)

[Roughasguts]

Navi leave it for the moment getting full rev's may have a lot to do with the weather conditions slowing down your boat at the time.

Wait for a better day first then see how much she is down on rev's, if at all.

Then the first thing I would play with is the timing.
Im not a great beleiver in adjusting the timing spot on with a light.

I'm more inclined to tweak the timing for best running and performance, for that particular motor, it all changes with age, and load, and what fuel octane it's running.

I have noticed in all me years that most times you can alter the timing way out of spec, on older motors and get them out of the doldrums.

Good to hear it's up and running though.

[Navi]

I'm back from sth straddie boat went really well not getting full rev's or as many as before but getting more speed 32 mph instead of 23 so I'm happy with that...

Thank you one and all who gave me advice....


cheers chris.

[Roughasguts]

Good to hear Navi, Adjust the timing a tad more, that oughta pick up the Rev's a bit.
But better still give it better fuel economy, you may find it may not be as good as it was also. But that's motors easy fix really.