Merc 3.0 won't get on plane! Only getting 3000rpm

[tbone999]

Hi, I have a 74 bayliner liberty that has been re-powered in 2006 with a merc 3.0 and alpha 1. I got it last year and love it. It is 19'6 and 2500lb I know a 135hp 3.0 is a little low hp for a boat this size but she's just my cruiser and I feel it should be able to get up on top of the water with out a problem. So as the title says I punch it and 95% of the times only get 3000rpm the other 5% I gets up and goes with out a problem. I have had no weight in it, had it loaded down, doesn't seem to make a difference......the engines starts and idles great and besides not going over 3000 rpm sounds great.......please help Thanks

 

[Starcraft5834]

What size prop do u have on it? Numbers should be stamped on inner collar...assuming your engine is healthy we need to know prop size . U should be getting 4400. To 4800 rpms out of that engine.. your probably over propped..ie. to much pitch for a 3.0 on a heavy boat..m

 

[Starcraft5834]

Ive got a 20ft 2500lb cuddy w 3.0 140hp. I use a 15x15 4 blade.. 4500rpm. 30 mph.. jumps up on plane in less than 5 sec.. use to have a 3 blade w to much pitch..had same problem u describe..less pitch and 4 blade cured it

 

[MikDee]

Is your timing advance working properly? With engine off, take off the Distributor cap, and grab the rotor, gently try to move it one way, or the other, it should move maybe 1/4 a turn in one direction, then spring back on it's own. If not, that maybe your main problem. Then you must take off the breaker plate (2 screws sideways), and clean up, and lube the weights, & springs. Then put it back together, and reset your dwell, then timing.

 

[tbone999]

The prop shows 17p and it's a three blade, the only thing with that is I have taken it to areas with strong tide flows and it has(not every time) jump up out of the water going against and two mins later won't get up going with the tide witch doesn't make since to me. And as for the timing advance I'm not sure I will go out and untarp it shortly and take a look Thanks Gents

 

[airshot]

Ha the outdrive unit been replaced? Also sounds like the incorrect gear ratio, should be a 1.98 or 2 for the 3.0, if the outdrive was replaced did they use the right gearing?

 

[Fastatv]

Hi, I have a 74 bayliner liberty that has been re-powered in 2006 with a merc 3.0 and alpha 1. I got it last year and love it. It is 19'6 and 2500lb I know a 135hp 3.0 is a little low hp for a boat this size but she's just my cruiser and I feel it should be able to get up on top of the water with out a problem. So as the title says I punch it and 95% of the times only get 3000rpm the other 5% I gets up and goes with out a problem. I have had no weight in it, had it loaded down, doesn't seem to make a difference......the engines starts and idles great and besides not going over 3000 rpm sounds great.......please help Thanks

As mentioned, your mechanical advance may not be working correctly, might want to check that out and do what MikDee has recommended. Also, I had a bit of a similar problem with my 3.0.....was pulling my hair out. I then decided to clean and dielectric grease every single electrical connection. Battery, all grounds, and every connector in the engine compartment. Since then, never had that problem again. Good luck