Z 272 wont rev more than 4100 rpm
 

I have a 1996 Z 272 BR. It weighs 6000lbs dry. It has a 2000 7.4 MPI engine with around 330 hp. The drive is a 2005 bravo lll. The gear ratio is 2.00:1 and my duo props,(perfect condition) are 22 pitch. at 4100 rpm it goes 37 mph, properly trimed up, 1/2 tank of gas. I get the same results when I'm alone or with 6 people. I still have 35 % throttle left on the stick. Throttle cable at engine is perfect. I should be able to rev up to 4800 rpm. I know it sounds like I should be changing the pitch to 20 and or the gear ratio to 2.2:1 but I think I might have a problem elsewhere. Engine compression is 150 lbs accross the board and the timing is set properly to 8 degrees at 600 rpm in gear. Engine runs strong with a good hole shot. I was thinking of having a marine shop check the engine with their computer. Anybody out there have a similar set up??? Any suggestions?

Thanks,
Paul

Re: Z 272 wont rev more than 4100 rpm
 

What do you mean, you "have 35% left on the stick"? I assume the problem is with the max. throttle possible at 4100? Or do you still have throttle to go at 4100 and 37mph?

Re: Z 272 wont rev more than 4100 rpm
 

I have the 454 magnum and at 4800I am at 53 mph, and I think I too have the 22 pitch props. is this new to you, and has it always done this?

Re: Z 272 wont rev more than 4100 rpm
 

To answer the first question, In the water, at 65-70 percent throttle I get 4100 rpm and 37 mph. When I continue to throttle nothing more happens. I checked the throttle body and cable and both work perfectly.
Iv'e had the boat for around 2 years. It has always been that way. Acually, before I pulled the motor I was getting 3900 rpm and 34 mph. I did replace alot of stuff and many sensors on the motor keeping it all stock using Merc and Quick Silver parts.
Are you pushing the same boat with your 7.4 mag? Do you know what your drive gear ratio is? And is your drive a Bravo lll duo prop? If all is the same, I should be getting 45-47 mph at 4800 rpm. Sorry for all the questions... Iv'e worked hard restoring the boat since I bought it. All has gone very well and the family is delighted with it. If only I can figure this out.

Thanks,

Paul

Re: Z 272 wont rev more than 4100 rpm
 

Paul,
I have a 98 z272. It has the Bravo 3 and the motor is the 454 magnum with about 385 horse. you are pushing 310 horsepower and the WOT range is 4200 to 4600 for the non magnum engine. Seeing as you have a 2000 motor and a 96 boat, i would guess the throttle issues are linkage fitment and cable travel. I am not sure about the ratios....but with your setup you should be able to hit 45 to 47 max.

Re: Z 272 wont rev more than 4100 rpm
 

Thanks for the information Mike. The first thing I did was verify the entire throttle assembly to be fully functional. I'm thinking it's likely to be one of the following. 1) Fuel restriction. 2) An electronic sensor or Distributor not advancing enough due to age. I'm installing a new distributor tomorrow afternoon. If that doesn't do it then it's off to the computer tech. I guess I should break down and have the engine checked with a Marine scanner/ tuner.

Thanks again,

Paul

Re: Z 272 wont rev more than 4100 rpm
 

Question... (I may have missed this) What ignition does your boat have?
Merc has had some issues with the ignition sensor in the distributor (I had to replace mine) cost is aroung 65 for thunderbolt. However, mine would not advance during hard accelarations and fall off.