Lack of Power

[albacore11]

Engine: Yamaha EFI 115

Boat: Bay 190

Prop: 13 X 19 Michigan Wheel Vortex

Issue: Boat will not drop down and plane. Maximum RPM is 4200 at WOT

Top speed is around 25 MPH, WOT, however in the chop today it stayed right at about 12 MPH at WOT.

Fuel Filter is fine, throttle linkage is fine, confirmed that we are getting full throttle.

I think the issue is the prop but the lack of RPM is a concern.

I forgot to check the mounting position of the engine. But there is a trolling motor mounted on the cavitation plate. There are NO trim tabs and there isn't a hydrofoil fin on the engine either.

All diagnoses are appreciated.

Chris

[Putershark]

So are you saying that NOT under a load, the engine will develop WOT of 5500 to 5800 plus RPM?
Is this the prop this boat has always had and how did it perform before?
Did you check the prop hub?
Have you taken the time to drain off / empty the fuel filters?

If the hub is OK and this is the prop that has always been on this boat, then I would say you have a fuel delivery or ignition issue of some kind. Your dealer can hook up the engine's ECU and pull a data dump to look for such items and in the mean time, I would pull the spark plugs and look for one that is wet or carbon fouled

[albacore11]

Since the prop is identified as a Michigan Wheel, I do not believe it is the original. It is the prop that came with the boat, I am its second user.

It does not develop 5000+ RPM, it maxed out at 4200 RPM.

The engine is not missing or anything, and looks factory new under the cowling.....pristine

[Putershark]

I would look on this thread for the link to the Yamaha performance guides for the 190 and that engine. Then compare your prop to the one tested

Engine performance guides

I would also guard against good looks as being an indication of function. I and my techs (as many here) have all installed brand new parts that were defective... Hence my saying when troubleshooting pretty much anything "I would much rather have known good parts, than brand new any day"

[HighTechRedneck]

I dont think the prop is the problem. I agree with Putershark and say you have a fuel or ignition problem.

The few things that come to mind are
water in the fuel
old fuel
fouled spark plugs
some extra weight some where. possibly water in the inner hull
could there be a problem with the motor not going all the way down.
bad spark plug wires.
I have heard of loss in power in a car with a bad ground wire.


just some random ideas
Good luck
HTR