Jack plate to big?

[Jasona5103]

I have a 07 blazer 180 pro v. Just repowered with a 2018 merc 150 pro xs 2 stroke from a 06 150 optimax. It had a 10" slidemaster jack plate. It was froze up. Replaced with a 14" jack plate. Now I've lost 1000 rpm top end. I would run 5800-6000 with the old optimax. Now I'm only turning 5000. Same prop 24 tempest plus. I can raise the motor and gain rpm but lose speed and water pressure. Could the jack plate have to much setback?

[pmgoffjr]

Very possible. The boat creates a swell behind it as it moves through the water, you want to be exactly at or just ahead of the top of that swell, behind it is a very bad place.

Now for the obvious question, are you out of break in on that motor? That's ten hours run time. It won't do much until the computer lets it go.

[Jasona5103]

Yes, the engine has little over 30 hours. I can raise the plate and gain more rpm but lose speed and water pressure.