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View Full Version : Help with 90 HP yammie please.



GavinW
25-04-2008, 08:15 AM
My problem is if i run the motor on full throttle on a flat/calm day after about 5 mins the alarm goes off and i have to shut her down for 5 mins to cool down, after that she starts up fine and i can run her on 3/4 throttle all day without a problem. Is there something that i should be looking at to rectify this or is this common with these motors(1990).

Thanks in advance

Gavin

FNQCairns
25-04-2008, 09:36 AM
Gavin are you propped well? this can tip the scales into overheat when near the top of the rpm range if you have a borderline problem already.

These engines are known to clog the head with deposits, replacement is an easy job, also one never really knows what is going on with the pump/block passages/thermostat/popets.

If you have a sticky/not fully opening poppet then there is the problem, any one or all of the above...you get my drift?

For cost effectivness start with the simple common and expected problems because of time/cost and work from there.

Personally I would pull the thermostat and poppets, clean/inspect/replace if nessesary then if no improvement move on, of coarse a lot depends on when the last time the pump was changed and if you have dredged sand -these thing only you can know.

You can also give it to a mechanic and get a 800+ dollar bill and most/all problem parts replaced but you may only need in reality a new poppet seal/seat or a clean around it.

Lastly if the engine is a little high this can do it also, mine is fairly high for economy at cruise but when up top I watch my water pressure drop away.

Cheers fnq

Noelm
25-04-2008, 10:18 AM
verry common thing, it is a "feature" of the old 90 yammies, the water jackets will be salted up for sure, sometimes a head removal and clean will get it going again, but other times,(usually) you need to remove every cover and thing you can find to un block it.

GavinW
25-04-2008, 01:50 PM
I purchesed the boat not long ago and although i am mechanically minded i know nothing about 2 stroke outboards so i might have to wear the bill for this one.

Does this sort of thing build up over time even if you flush your motor well after each use?

Once unblocked is there anything you can use other then flushing to keep it squeeky clean ?

Can anyone reccomend a good outboard mechanic in Melbourne they have used that isnt going to rip me off blind?

Thanks

Gavin

Outsider1
25-04-2008, 02:55 PM
I purchesed the boat not long ago and although i am mechanically minded i know nothing about 2 stroke outboards so i might have to wear the bill for this one.

Does this sort of thing build up over time even if you flush your motor well after each use?

Once unblocked is there anything you can use other then flushing to keep it squeeky clean ?

Can anyone reccomend a good outboard mechanic in Melbourne they have used that isnt going to rip me off blind?

Thanks

Gavin

Gavin,

Ausfish member BM should be able to help. Send him a pm.

Dave

BM
25-04-2008, 04:25 PM
Thanks Dave :)


Gavin,

Once cleaned out it will stay clean for the next 10+ yrs with regular flushing. It will still build up salt over time. Its just a Yamaha thing due to the narrow water galleries.

I did a 50 Yammy a little while back and its a lengthy job. Powerhead off so you can get to all the sideplate bolts. Some of the little 10mm bolts in the waterjacket cover on the head and also the sideplates will break in getting them out.

The head will be gunked up with dry whitish brown solidifed salt and the water jacket side of the head will be gunky too. The sideplate will likely have a good deal of salt buildup and the bypass holes from the sideplate area to the cylinder galleries will be blocked too.

If the previous owner didn't drive above say 4000rpm they would not have known about the problem as it usually only shows itself at high rpm/high load.

Where in Melb are you?

Cheers

black runner
25-04-2008, 06:28 PM
A mate of mine has an earlier 4st suziki that he was having difficulty with getting a good telltale stream. He had the pump changed thermostat amongst other things including hoses and fittings. $600 later he ran some "Salt Away" through it as it was getting close to his annual camping fishing trip. All clear and has been good for 12 months. Some say it's snake oil but it seems to have worked on this occasion.

Cheers

Noelm
26-04-2008, 07:40 AM
even though it may be "snake oil" I guess it can't hurt to at least give it a try, but this is a very common problem, especially with the 90HP, I have had 2 and they both suffered the same condition, as did my mates on his cat, both over heated above about 4,000 RPM, below that, no problem at all.

BM
26-04-2008, 08:05 AM
Perhaps the saltaway might work on the clear coloured jelly like buildup but not the dry whitish brown stuff that needs to be scraped out.

I know a bloke who has been testing those salt removal products with a view to developing one that actually worked. They have had very limited success with the available products in their testing.

Cheers

GavinW
26-04-2008, 10:26 AM
Thanks for all the info , sounds like a common problem over 4000 rpm. I am located in Hallam (near Dandenong). The motor has a good telltale stream at all rpms , but i now know you ned to look further than that when purchasing a boat.

I should have got the "Boat inspections made easy" manual.

Thanks Gavin

GavinW
26-04-2008, 02:38 PM
Can anyone reccomend a good outboard mechanic in Melbourne they have used that is not going to rip me off blind? I am in Hallam (near Dandenong) but am prepared to travel to get a good job done.

Thanks
Gavin

dnej
26-04-2008, 05:58 PM
Gavin,
Take a look,BM was aking you about your location
David

Dean1
26-04-2008, 07:41 PM
Thanks for all the info , sounds like a common problem over 4000 rpm. I am located in Hallam (near Dandenong). The motor has a good telltale stream at all rpms , but i now know you ned to look further than that when purchasing a boat.

I should have got the "Boat inspections made easy" manual.

Thanks Gavin I bet its the thermostat. My 70 yammie was doing the exact same thing, lucky i have two of them on my cat so my mechanic told me to swap them from one to the other and suprisingly it fixed it. One mustnt call for as much cooling as the other ( thermostat doesnt have to open as much as the other). Their easy to access.

GavinW
26-04-2008, 09:04 PM
PM sent to BM thanks David

Sounds like there could be a few things to check to solve my problem.

reel-em-in
26-04-2008, 10:02 PM
Try the thermostat first. I had exactly the same problem last week on my 70 hp which after removing a small amount of buildup on the thermostat itself seems to have fixed the problem. Interestingly the housing was extremely clean just had buildup on the thermostat body ityself.
Total cost of repair $nil .

Good luck