gear/ engine problam

[Miki]

hello,
i have a gear / engine problam.
There is a situation that, when the engine is idle, the columns go up to 5000 rpm.
And when the engine is in gear the columns only up to 3,000 rpm
what Could that be? And what i need to chack first?
i have 5.7 mercruiser engine

thanks

[mmwjr]

First never run an engine up to 5000 rpm in neutral as this can damage the engine.

So in gear you only hit 3000 rpms? What boat model? What outdrive?
How many people on board? What is the condition of the prop? Any marine growth on the hull?

[Miki]

thanks.
we been 3 people on the boat.
the model maxum 2400 scr, mercruiser 5.7 engine.
the hull is clean.
only in gear i can hit only 3000 rpms and i cruise only 7 m/h

[Miki]

the model of the boat 1998

[mmwjr]

Ok so you have the same boat as I do. Is this a new issue if not what has changed since it did perform well?

Prop in good shape? Is the engine producing full power? Tuned up? Compression test on all cylinders. You may not be firing on all cylinders.

[Miki]

I bought the boat not long ago so it is difficult to compare
The engine is original with no improvements.
i did not do Compression test
but there is no licks of oil or fuel
the prop is in good shape
what it can else be?

[mmwjr]

Tune up but I would perform a compression test first. I have had engines with zero compression due to a tuliped valve. Idle and ran smooth but short on power.

[Miki]

ok i will try do this
it can be problam in the gear?
thanks

[mmwjr]

The transmission in these is very basic forward reverse neutral. Either works or not.

[shrew]

Overpropped?

[Miki]

no, from what i now

[Miki]

You can bring me recommendations for Tune up's?

[mmwjr]

Originally Posted by Miki

You can bring me recommendations for Tune up's?

See manual for your engine under the Documents section of this site.

[mmwjr]

Originally Posted by Miki

no, from what i now

What size prop do you have?

[donald]

The paper work I have on my 95 2400SCR w/ 5.7 states it came with a 14.5X17 prop!
I am running a 19p prop and it only turns about 3500RPM's!
Ck prop pitch
!
My 2c!
Don

[mmwjr]

My 1997 2400 SCR came with a 5.7LX and Bravo 2 drive swing a 18 3/4 diameter by 17" pitch prop. It achieves 4800 rpm with 3 souls on board.

[Miki]

i have the original prop
dont remmber the size

[mmwjr]

Originally Posted by Miki

i have the original prop
dont remmber the size

How do you know this? You said earlier you recently bought the boat and it's nearly 20 years old. Most of us damage a few props in that time span, just part of boating.

[Miki]

ok, i will check this..
and let you now