Not Enough RPM's

[Chris3515]

I recently purchased a boat with a 2002 90hp 2-stroke Yamaha with 200 hours on it. Engine starts and runs great up to 3800 rpms but thats all Im getting out of it. Ive already determined that we have the right prop for the boat, tried different tanks, fuel lines, with and without water seperator and for some reason it accelarates smoothly up to 3800 rpms (maybe 3900-4000 with a really light load) but as I throttle further, no response. Anyone else have similar issues, any recommendations? Thanks

 

[cousinabe]

Re: Not Enough RPM's

what's the complete model number off of the port side of the bracket?
does pumping the primer ball have any affect?
Is the motor bogging down when you try to hold WOT?
Has it ever run right?

 

[Chris3515]

Re: Not Enough RPM's

Im going to have to check on the model number (boat isnt at my house right now).
Pumping the primer ball doesnt help.
It definitely doesnt feel like its bogging down at all, unlike a previous Yamaha I had, which constantly sounded bogged down at 2200 rpms, but would power through it.
Your guess is as good as mine as to if the previous owner even knew the engine wasnt running to full potential. I would like to think that out of factory, the engine ran right but I cant confirm that.

Any help is greatly appreciated...

 

[cousinabe]

Re: Not Enough RPM's

i'm not sure if you saw this post. your engine is probably the 90TLRA model... it's the only 90hp listed for 2002.

This post addresses a 2003 150txrb which is also a carb motor as well... i'm not sure about the true comparison of the two, but it may give you some insight.

http://forums.iboats.com/showthread.php?t=290240

hopefully the experts will chime in with some info for you.

 

[rodbolt]

Re: Not Enough RPM's

from the Yamahay odds are high that motor ran correctly.
however Yamaha did NOT mount the engine to the hull nor did Yamaha select the propellor for correct dia and pitch.
thats all left to the hull manufacturer or the shop that rigged it.
so myself it that boat showed up at my shop with the information provided I would install test wheel YB1620 and back it down the ramp and see if it would turn up to 5100-5300 RPM. if it will reprop it if it wont I would know I had an issue with the engine itself.
if the shop has an IDC 2000 or 2003 model dyno then it should read about 1875 PSI at 5100.
remember, an outboard is not like a chevy or a ford.