No power after engine reuild, Please Help!

[doral270]

Hey everyone,

I have a 2001 doral 270SC with 7.4 L MPI. The engine overheated last year and had to be rebuilt. The rebuild was conducted by a reputable company and a Dino Test was even conducted and showed full horsepower and RPM range.

Upon recieving the boat back after 2 1/2 months of service work, the boat seemed to be running ok, however, as soon as I loaded the boat with 6 people we had difficulty getting boat on plane. This year, boat will hardly plane with 2 people and can only reach 3600 RPM and 32 mph at full throttle and slighly trimmed up.

Prior to engine damage and rebuild, boat was running top end at 46 mph and 4800 RPM. I do smell some gas/exhaust at about 10 mph. Can anyone help with possible senarios. I have ruled out a prop change for obvious reasons.

Thanks,

Tim Ness

 

[Limited-Time]

Re: No power after engine reuild, Please Help!

If the rebuild dynoed (sp)OK I would suspect an exhaust restriction. How "hot " was the over heat? Could be the exhaust flappers burned off and are now blocking the exhaust outlet.

 

[DTHOUSAND]

Re: No power after engine reuild, Please Help!

Start by checking your plugs see what color they are, that can tell you alot about what is going on in the cylinder itself

 

[doral270]

Re: No power after engine rebuild, Please Help!

Re: No power after engine rebuild, Please Help!

thanks for the timely replies,

The engine got hot enouph to warp the heads and waterlock the cylinders. All valves gaskets and bearing replaced, and cylinders rehoned. The exhaust flappers were at least checked if not replaced and were fine.

I did check four of the plugs that were easiest to get to and all were tan in color and appeared to be burning hot. I will check the rest this weekend.

Is there any chance I could have a timing problem or fuel flow problem? I checked the throttle linkeage just to make sure that I was getting the full stroke. No problems there. The engine sounds to be running smooth just lugging down and RPMs won't wind up.

Thanks again

 

[Coors]

Re: No power after engine reuild, Please Help!

Have you checked for crap in the fuel?

 

[DTHOUSAND]

Re: No power after engine reuild, Please Help!

I would change out the water seperator and change any in-line filter, also check your cap & rotor. I know in mine the thunderbolt ign. the sensor would develope rust and would cause my engine not to rev up.Also did you take the distributor out of the motor after it was dynoed? Good luck let us know what you find

 

[hudman]

Re: No power after engine reuild, Please Help!

Check your timing, it could have backed off. boat motors will run with timing off, because they dont have all the add ons that a car motor has, such as air pump and air conditioning. I had one one time running with timing set at straight up TDC, when i timed it correctly, doubled the power and cut fuel usage in half.