Still can't get this thing to work

[bodine]

1987 24ft bayliner trophy i/o 5.7l omc with sei mercruiser conversion. I had to replace the engine and decided it was time to upgrade the outdrive to mercruiser. As soon as I got it on the water I knew something wasn't right. It would not plane out! For the first year, I talked with sei over gear ratio and outdrive angle as possible issues. After some extra modidications, per tech support, it will sorta plane out and run about 18mph and 3000rpm at half throttle compared to 28mph before. The kicker is when I go full throttle it will get to 23mph and 3200rmpm compared to 35-38mph at 4500 rpm. I have tried multiple props, replaced carb,intake,exhaust,ignition,ect. boat is using twice as much fuel as it should. Boat seems to nose dive at speed. I still suspect outdrive angle issues. I am hoping that someone might have the answer. The boat has been parked for the last year since I ran out of ideas. At this point, I feel like I should have rebuilt the omc.

[admin]

I'm sorry your having issues with your SEI product. Was the engine installed at the same time as the drive, or did you run that engine with the old drive? Just curious if the engine is making the right power.

Did you confirm the ratio in the drive? What ratio was your old drive? Do you have more room to modify the drive to get a little more trim in without hitting the shift lever on the transom assembly?

We have only heard of a couple other people having issues, but that was on a much larger boat.

Tech Support

[bodine]

I did run this engine on the old drive for a short time. The performance was good. I had discussed gear ratios with tech support, they tell me its correct. I don't know how to physically verify it. I wasn't sure how much more I would be able to modify the drive. I have ground the tabs off, next it is going to get into the spacer area. Looks like plenty of room between shifter and transom assy. I am willing to cut if you think it will fix it. By the, last time i ran it the impeller spun on the shaft and melted my flappers and the plastic tubes in the outdrive. Is this a common issue?

[bodine]

Went and checked shifter clearance, there is no more room to modify the drive. How much larger were the other boats having issues? Maybe I have the wrong gear ratio?

[admin]

The other boats having issues were 29-31 feet long. To check the ratio, pull the top cap and count the teeth. 20-22 is a 1.47 and 24-24 or 20-20 is a 1.62. For your old drive, do you have the model number and serial number? Maybe we can confirm what your old ratio was.

Tech Support