Low compression

[Check]

I got a 2002 RX DI a friend. It starts right up and sounds great out of the water. When I put it in the water with a load on the engine and open upon up the throttle it would bough down. I did a compression check got 85 psi on both cylinders. I did a top end with a new cylinder head, pistons and rings. When I did another compression check on new head I got the same pressure of 85 psi.
Is there something I am missing

 

[mikidymac]

Sounds like a bad compression tester.

 

[rotaxrule1]

I had a similar issue with mine. Pull the spark plug wire and put it on the grounding post on each cylinder to make sure it will run on each cylinder independently. If not, your weak cylinder might have something wrong with it. In my case, it was a shattered Reed valve.

also, your air pressure and fuel pressure need to be at 80 psi and 107 psi, respectively. You’ll have to buy or make a line tester for those.

 

[etemplet]

If the engine is bogging you likely have a fuel issue. Need to test fuel pressure, air pressure and air lines to the rave valve solenoid. Make sure everything is connected. You might have to send the injectors out for cleaning. Get some spark testors which let you know if both cylinders are getting fire. Good Luck !!