Loss of power on a new rebuilt motor need help

" I just rebuilt a 2.5 litre m

" I just rebuilt a 2.5 litre mercruiser and the motor runs good the problem is that there is no power when running the boat.the boat does not run over 7mph Im running around 3,000 rpm with the the trottle wide open.Does anybody have any input on this.The boat is a 1986 sunbird it came with 140 hp 3.0 but the block was cracked so I found a 2.5 mecruiser that I rebuilt.I used the 3.0 head that came off of the old block. "

" Not sure if that is an engin

" Not sure if that is an engine problem or transmission. If the engine is turning freely and sounds strong, then it most probably is running strong. If you have a stern drive I would check the washers and nuts around the prop for proper torque. I had a similar problem when I rebuilt my engine, I put it in the water, and vroom...then engine worked. Add torque, and the prop would not spin...it just slipped.

If the engine is turning over at 3000 RPMs, it is turning the crank at 3000RPMs, the problem is probably not the engine.

Hope this helps

Eric "

" Wide open throttle should be

" Wide open throttle should be 4000 to 4200 rpm.
Since youve downgraded in power, you will have to change your propeller pitch. Using the 3.0 litre cylinder head will not necessarily increase power.
Take a compression test(very important to do first), before you proceed with anything else.
Was the outdrive lower unit ever changed?
If you need any info or parts just call Dania Marine 1-800-748-7739.

Thanks, Gabriel "

" I have a 30' Luhrs with

" I have a 30' Luhrs with twin 318's. The port engine uses almost twice as much gas as the starboard engine, Both have eldlebrock carbs, props have been redone, no leaks in the fuel tanks, engines turn same rpm's. Any sugestions would help. Port engine carb was recently rebuilt because I could not generate same rpm's as starboard engine. The mechanic said he thought the secondaries were not opening up. "

" Hi,can anyone tell me if the

" Hi,can anyone tell me if the 3.0 4cyl mercruiser head will fit on the 2.5 4cyl block..is it a direct bolt on or do you have to do any mods..Thanks Terry "

I have a 305 mercruiser and I

I have a 305 mercruiser and I found white just in the heads.I checked the exhaust for holes and found none.Could it be a head gasket or cracked block?

"I have a 470 Mercruiser that

"I have a 470 Mercruiser that overheats at the higher RPM's. I've replaced the thermostat,cap and OD impeller and it still runs hot. Could this be a head gasket problem?"