Only getting 4200 rpm @ wot???

[Maxumhiredhelp]

Hi again all

I am hopeing to get an idea of what is wrong with My in laws Vessel. the Vessel is a maxum scr-2900 with a 5.7 liter eng and a Bravo 3 outdrive.

The Problem is We are only getting a maximum 4200 rpm @ wot, I dont know what happened just a few dyas ago we were grabbing at least 5500 rpm.

I have yet to look at the Rotor and cap and the ignition system, Was hopeing to do that later to day. I know we are geting wot as i have looked to the throttle body and butterfly valve is pegged open. So mechanically its at wot.

Could it possible need a tune up or maybe i need to dropped under the boat and check the out drive for fowling????

Any ideas would be appreciated as i have had AWSOME support from the forums here, Keep up the good stuff

Chris

[seapuppy]

yes.....start with the bottom...if it's crapped up with a mess of growth....then no matter what your doing will get it too WOT...

if that doesn't help..then start with a tune up...does it have points or solid state ignition???..probably the SS ign....if that's the case...then when was the last time you replaced plugs..distr cap...rotor....and wires??...

how bout the gas...is that ok???...I mean fairly fresh??...filters...when was the last time you replaced the fuel filters.????...if the engine is carbed ..could be a problem with the carb or the filters....by the suggestion that you were getting 5500rpm..I'd say it was MPI...which I would suggest that you clean the intake screen ...

SP irate:

[Maxumhiredhelp]

It should not be growth or something along those lines it was hauled and cleaned this winter and only been in the water about a month. But i will be sure to take a look. The father In law may have picked somthing up here in the Solomons island area of maryland.

Will take a better look at the screen it seemed to be pulling air fine while i was checkng things while under way it appeared to be pulling good air. BUt I will look.

Yes its a Solid state ignition, I will take a good look at all filters and ingnition items as we have mentioned.

Hope We fine it soon.

Thanks a million again

Chris

[yorkcoparamedic]

Man thats crab pot haven down there. Yeah check for a line or something around the prop or shaft.

I had something very similar a couple of years ago. I picked up someones underwear and the whole nasty thing got pulled down in behind the prop around the thrust plate. You might need to remove the prop to check for sure.

Good luck!

[Maxumhiredhelp]

Well here is an up date,


Changed everything in the ignition system, except plugs and plug wire.

Well we gained a few hundred RPM's, But still lacking quiet a bit like around 500 or so. So I guess its time to go into the water and take a look.

If anyone else can think of a few things i missed let me now for now It's time to get wet

Cheers All

Chris

[Big Joe]

Don't know if you figured this out yet, but I work down on base (Pax River) and I know a BM2 who maintains the mercruisers on their port boats. He does lots of work on the side and I usually pay him in beer. Can't beat that!

[ss3964spd]

Are you certain the 350 Mag is even supposed to spin to 5500 at WOT?

Seems excessive......

Dan

[seapuppy]

if it's an mpi engine..it will spin right up to redline...or the rev limiter..whichever is first...
if it's carbed..then you should be between 4200-4800 rpm..
as for the 500 falling short....that could be tach error...or growth on the hull..


SP irate:

[ss3964spd]

Originally Posted by seapuppy

if it's an mpi engine..it will spin right up to redline...or the rev limiter..whichever is first...SP irate:

Understood, but will it spin to red line/rev limiter at WOT under load?

[seapuppy]

provided it's propped properly......yes......my 2700 would hit rev limiter....


SP