85hp Yamaha wont go over 2000 rpm

[mydauphin]

hi all
I have 2 stroke 85hp Yamaha. Will rev in neutral to 5000 rpm, will rev in land to 5000 rpm forward or reverse. Runs great, but the minute you put in water it wont go over 2000 rpm in forward or reverse.

Let me tell what I have done.
Replaced plugs, cleaned carburetors, good gas, checked choke throttle linkage.
I believe problem is electrical, perhaps some kind of get home rev limiter, computer issue.

I am looking forward for ideas on this, I am going crazy

[powerabout]

How many cylinders is it running on?
being a 2 stroke it will probably do 5000rpm on one cylinder

[Petros]

I do not know a lot about that particular engine, but it sounds like you are down on power out put. Testing cylinders for power out put can be done with the "drop down test", with the engine idling fast, you first pull one spark plug at a time in turn (use thick rubber gloves). The rpm should drop about the same with each wire pulled. I would not jump to replacing your ignition system just yet, usually the electronics are pretty reliable, so eliminate everything else first.

It could also be fuel starvation. For some reason not getting full fuel flow at higher engine demand; check filter (if any), blockage in fuel line, tank inlet, even blockage in the carburetor or EFI system if you have one. Clean the system out.

If the engine runs too lean it would act like that too. Check for vacuum leak in intake manifold, that all fittings and vacuum lines are connected and not leaking. If there is a rubber boot or inlet check there are no cracks. An easy way to check for vac leak is to spray carb cleaner in and around the intake manifold, carb and all vacuum lines with the engine running. IF the engine speeds up when you spray at a particular place, you found the leak (test the engine response by spraying some in the inlet, running lean the engine should speed up, running rich it will slow down).

Could also be air intake is restricted, check air filter and air inlet for blockage, a Or the throttle is not fully opening, you can check that by visual inspection when the engine is off.

Good luck.

[Fanie]

Hello Mydauphin,

I had one of those 3 cyl 85hp 2 stroke Yammies, one of the best, almost runs with the 115's.

It sounds like it doesn't want to rev up under load, ie no torque. To add one more thing, check if your timing advance is working.

[mydauphin]

Thanks all, Timing advance seems to be working. All coils are working test coils with engine rooming. I will looking at it more later tomorrow.