I just bought a used Bayliner Trophy 23 foot and the engine is OMC 5.7
1989 (model 574 APRMED), i believe it has 250 HP. The prop is 15'' x
17''. But the max rpm I get is 3400. Is that the maximum rpm on this
type OMC engine? I should think it lacks at least 1000 more rpm. I
believe the engine should be able to get at least 4400 rpm at WOT. The
max speed i currently get is just 24 knots. The engine seems fine and
I just replaced the spark plugs. Anyone has ideas of what could be
wrong?
Thanks
Jens-Erik
Nuuk, Greenland
My boat: http://www.123hjemmeside.dk/Nukappiaaluk/1442331

"Jens_Erik" wrote in message
ups.com...
I just bought a used Bayliner Trophy 23 foot and the engine is OMC 5.7
1989 (model 574 APRMED), i believe it has 250 HP. The prop is 15'' x
17''. But the max rpm I get is 3400. Is that the maximum rpm on this
type OMC engine? I should think it lacks at least 1000 more rpm. I
believe the engine should be able to get at least 4400 rpm at WOT. The
max speed i currently get is just 24 knots. The engine seems fine and
I just replaced the spark plugs. Anyone has ideas of what could be
wrong?
Thanks
Jens-Erik
Nuuk, Greenland
My boat: http://www.123hjemmeside.dk/Nukappiaaluk/1442331


It's hard to tell, not knowing what the original prop was, how much that
boat weighs, (is it waterlogged?) or how you have it loaded.

Assuming there are no problems with the engine, coil, carb, etc., it is
possible that the previous owner installed a higher pitch prop, thinking it
would go faster (common mistake). FWIW, one of my first boats, a 1982
Century with a 5.7 L engine and alpha drive had a similar prop (17 pitch)
when I first bought it used and the engine would only get to about the same
RPM (3200-3400). I had to drop to a 12 pitch prop to get the RPMs up to
over 4200.

RCE

On 15 May 2006 05:52:18 -0700, "Jens_Erik"
wrote:
I just bought a used Bayliner Trophy 23 foot and the engine is OMC 5.7
1989 (model 574 APRMED), i believe it has 250 HP. The prop is 15'' x
17''. But the max rpm I get is 3400. Is that the maximum rpm on this
type OMC engine? I should think it lacks at least 1000 more rpm. I
believe the engine should be able to get at least 4400 rpm at WOT. The
max speed i currently get is just 24 knots. The engine seems fine and
I just replaced the spark plugs. Anyone has ideas of what could be
wrong?
================================

It is difficult to say what the problem is but something is definitely
wrong. I have the same engine in a boat of about the same size and
weight and it tops out at around 4400 RPM and 31 knots, also using a
15 x 17 prop.

Have a good mechanic check out the engine. It could be anything from
poor compression, ignition problems or the carburetor, but it is not
developing full power.

Jens-Erik

You should be getting more RPM's out of the boat. Two things I would
look for. First, I would remove the distributer cap and make sure the
advance isn't stuck, holding the rotor you should be able to rotate it
freely about a quater turn in one direction, and it should snap back
when you let go. If that's stuck some silicone spray should help free
it up. The next thing I would look for is the secondaries on the carb,
if it's a four barrel carb. With the engine off place the throttle at
full throttle. The secondaries operate by either mechanical or vaccume
action. The mechanical linkage should move freely, if it's mechanical.
If it's a Holly carb it has vaccume secondaries, again, make sure
everything moves freely, if it does you may need to repair the vaccume
secondaries (it's easy, just get the part and replace it). Also, make
sure that little hose going to the vaccume actuator isn't leaking.