Boerdoc1 update sportjet 90

[boerdoc1]

Some good news for all who have trouble with these. I too had problems with this motor. My magnets broke and it would not start.
So through the info here I made some changes.

I replaced the flywheel with a #859241T10 also referenced #817494A2.

I matched it with a trigger #817029A9 (Reference Part #: CDI 134-7029-3)

I also replaced the stator just in case with 398-832075A-4 - A21.

My engine has the cdm upgrade by the way.

The good news is that my boat starts right away. The new flywheel and trigger caused me to have to change the coil order due to how the trigger works but it works great.

After tuning the carbs and timing I got it up to 35 mph with 280lbs fo passengers on board. That is faster than ever.

If you are struggling keep trying as it is worth it when it works.

 

[ranman6]

Re: Boerdoc1 update sportjet 90

You said you have a cdm upgrade, what is that, and do you have part numbers.

I had mine out this week-end and had it wot at 30 mph and couldn't get it to go anymore, I know it use to have more power and maybe this upgrade might do the trick?


Thanks

 

[boerdoc1]

Re: Boerdoc1 update sportjet 90

cdm is a different ignition system. I do not think it is a performance issue. More of a reliability issue. I posted it because the parts I used may be specific to cdm and not the original cdi ignition. My boat is stock otherwise.
I did have a bent ride plate that I removed ,straightened and used a grinder to smooth the edges that had casting burrs on it. I painted it after also. I removed and cleaned the carbs and vent tubes. Then I walked through the tuneup in the manual. My impeller clearance is .010 in..

http://motorka.org/doc/mercury/service_manual/jet/SJ90_120_95xr_125xr_831996r1/cover.pdf

After timing and carb adjustment I was able to hit 35. It took some on water adjustments to get the top speed and holeshot adjusted but it was worth it. When I was at 1 1/2 turns out on the carbs I would hesitate out of the hole. I leaned it a bit and it is very responsive now. I am probably at 1 1/4 turns out. Then I timed for wot top speed. I do not have the # of the timing off hand and the boat is not in the water now to check.

I am not an expert but this is what worked for me.