3.0 mercruiser not getting on plane

[benjjordan]

I have a 17ft Mark Twain 175BR and the first time I took it out on the water it would not get up on plane (under WOT) and was pulling to the right HARD!! It had a hydrofoil on and after taking it off and trying again, it got up on plane but not quickly and was not pulling. Does this sound right? My prop is 15X17, how do I get more hole shot? Should I lower the pitch to 15? I believe my WOT is around 4800, can't remember right off hand. Any information would be greatly appreciated.

 

[Silvertip]

Re: 3.0 mercruiser not getting on plane

There is no reason a 3.0 shouldn't pop a 17 footer on plane in a heartbeat. So -- here are things to check:
1) Water soaked foam can add hundreds of pounds to a boat.
2) Is the engine making full power (good compression, tuned up, good fuel).
3) You said WOT rpm is 4800. Is that what you see on the tach?
4) Check the prop for a spun hub.

Changing props is not a solution for a tired engine or a boat problem. You need very accurate OBSERVED rpm and speed numbers and verification that everything else is in order before you begin spending money on props.

 

[Bondo]

Re: 3.0 mercruiser not getting on plane

Ayuh,.... My guess is either the motor isn't runnin' Right,...
Or,...
Somebody put the wrong ratio drive on it....

It oughta Pop outa the water with a 17" prop...

 

[rednecktech00]

Re: 3.0 mercruiser not getting on plane

I have a 17ft Mark Twain 175BR and the first time I took it out on the water it would not get up on plane (under WOT) and was pulling to the right HARD!! It had a hydrofoil on and after taking it off and trying again, it got up on plane but not quickly and was not pulling. Does this sound right? My prop is 15X17, how do I get more hole shot? Should I lower the pitch to 15? I believe my WOT is around 4800, can't remember right off hand. Any information would be greatly appreciated.

I have the very same boat. My originals 3.0 engine had a 19 pitch prop. When I installed a new 2009 engine, it was turning way too fast so I had to upgrade to a 21 prop. Something is very wrong if it is not getting up on plane with a 15. Might be the weight of the boat due to wet foam as suggested. Have you checked the compression on the engine? Also, mine gets water in the gas tank really bad. I carry a portable tank for whenever it isn't running right.

 

[benjjordan]

Re: 3.0 mercruiser not getting on plane

Sorry it has taken me so long to respond. It sounds like it might be waterlogged foam because the engine seems to run just fine. Just to make sure though how do I check the compression? Also, What is the easiest way to check for waterlogged foam? Thank you guys for all your help.

 

[steelespike]

Re: 3.0 mercruiser not getting on plane

for a compression check you'll need a compression gauge.You remove the spark plugs and put true gauge into the plug holes one at a time and crank the motor for a few seconds Read the pressure on the gauge and release the pressure before each cylinder.
Should be at least 100psi and within 10% between cylinders.You may want to check the timing is set right and advancing as it should.
The foam is under the floor select a spot near the stern to make a small hole, 1" or so,.
Be careful, make sure its the floor not the bottom.Just drill the thickness of the floor surface so you can feal and possible remove a little foam.

 

[benjjordan]

Re: 3.0 mercruiser not getting on plane

thank you.. I will hopefully try this tomorrow. Im guessing you can probably rent a compression guage from autozone or something?

 

[steelespike]

Re: 3.0 mercruiser not getting on plane

I think you can.