Twin 94 150 Yamahas rpms?

[Pursuit2550]

I have a 91 Pursuit 2550 with twin 94 150 yamahas. At WOT both engines run around 44-4600 rpms@42-43mph(GPS). If I let of the throttle to 3/4 throttle I maintain the same rpms and speed. The props are 19's. Does this sound like a engine or prop problem. I have not done a compression test yet, I will on Wends.
Thanks

 

[rodbolt]

Re: Twin 94 150 Yamahas rpms?

find a real dealer. place the test wheel on the engines and back it down the ramp.
standard rotation should spin it about 4800 left hand rotation about 5100.
if both motors spin up then your way overpropped and begging the motors to puke parts.
if all is well then prop it so the engines can spin 5400-5500 RPM.

 

[Pursuit2550]

Re: Twin 94 150 Yamahas rpms?

Can I run the engines at 3/4 throttle without anything happening to them for now or is it a bad idea. I figure if 44-4500 rpms at 3/4 sounds about right for that engine. My problem is the WOT rpms. I will be checking everthing out this weekend, I dont want to blow the engines thats for sure.

 

[Pursuit2550]

Re: Twin 94 150 Yamahas rpms?

Well I just check the compression on both engines. Both engine 100-110. Whats my next move. I am going to replace the fule lines since I found a leak by one of the primer bulbs. And I am going to change the spark plugs.

 

[rodbolt]

Re: Twin 94 150 Yamahas rpms?

based on the information provided? I already told you the next move.
your choice.

 

[Pursuit2550]

Re: Twin 94 150 Yamahas rpms?

Rodbolt I understand your point but I just bought a house and the boat, I dont exactlly have extra money to take it to a dealer. Here in Miami the going rate is around 80 dollars an hour. I dont want and have the money to spend for someone to tell me that the engine are fine. Maybe there is little things to look for and do myself before taking the dealer route. Maybe my engines are to low, maybe carbs. are dirty,etc. etc. Little things that I can do at home would be great. I will not be taking out the boat anytime soon since I just bought the house and will be working on it for sometime. If anything I will just take out the boat to test little things that I have done to see if they made a difference. Like I said before the cavitation plate is below the water is this something thatcould be afecting my RPMs. I can move them up 1 hole and check to see if it makes a diference. Anyways thanks for your help and advice.

 

[rodbolt]

Re: Twin 94 150 Yamahas rpms?

not busting your chops. dont care how much money ya do or do not have.
what I said was what I meant.
based on the information you supplied there is not a lot I can say.
throw the speedometer in the trash. it has no meaning for a technician.
we realy really dont care.
what I care about is the engines.
have they ever turned 5300-5500 RPM on that hull? if not it may be over propped. over propping will kill and engine as sure as an overheat or a lack of oil.
should take less than 30 minutes to spin them both up on a test wheel or a Dyno.
if you dont know the motors its the first place to start.
can the engines actually make power??
once we determine the engines can make power as designed with the proper test wheels we can discuss propping issues.
keep pushing them and they may go ahead and die.