sport jet 120 please help!!!!!!

[`Mike Burke]

I have a 94 sea rayder f-13. The boat originally had a 90 horse power sport jet in it. I put in a 96 sport jet 120 xr. The only problem that I have now is at wot the boat goes 36 mph. If I back off the throttle a little bit the motor picks up rpms and tops out at 41 mph (this is with one adult). So why do I have to back off the throttle to get more rpms. I just rebuilt the carbs and put them back on, they are in sync. I just don't understand because it has a throttle stop so it's not like the butterflies are starting to close from over throttling. Throttle cam is in line with roller. I know the timing is 32 deg. btdc while cranking and 30 deg. at wot. I don't know if it's retarding itself too much at wot. I plan on checking timing soon. Here's what I've done so far. New plugs, rebuilt carbs, new fuel pump, new fuel filter, new starter, new starter selonoid, and it has the blue stater. Impeller to wear ring is fine and would'nt cause this problem anyway. Could the rev limiter or coil pack be doing this. Engine starts great (hot and cold). The only thing I have'nt replaced yet is the plug wires. And probably will just order anyway. Any help would be greatly appreciated, I have a service manual and I'm stumped!

 

[kend301]

Re: sport jet 120 please help!!!!!!

Mike ,
Sounds to me like you are hitting the rev limiter , It will start to drop cylinders to keep the revs down , this floods the plugs briefly and they just do not make power when they come back in , Put a Tach on it and see if this is the case , rev limiter should be set at 5800 rpm , if it is adjust the throttle a little to keep this from happening. If it is happening below 5800 rpm you may have a bad rev limiter . Or you can disconnect the black / yellow wire to the rev limiter and see if the problem is still there , If it is look at carb adjustments and or jetting. If not note the rpm you are turning and if it is over 5800 at full throttle , the rev limiter is doing it's job . DO NOT run the boat over 5800 for a long time , lots of engine parts flying everywhere will be the result !

 

[`Mike Burke]

Re: sport jet 120 please help!!!!!!

I will try that on the nexy outing. How do I hook the tach up, I don't recall seeing a pulse wire. Thank you for your response.

 

[kend301]

Re: sport jet 120 please help!!!!!!

should be gray wire out of voltage regulator, should trace to main engine harness plug and end close to ignition switch not hooked up to anything.