only 9mph @ 4000rpm !!!

lekmedm · Sep 3, 2009

After having gone through much pain to work out cooling issues with my OMC 460, I finally have the engine running great - at least while docked!

I finally got to take it out this season and only got to 9mph @ 4000rpm checked by GPS. Now, I don't expect a 26' cruiser to be a rocket, but I think it should do better than that. I have a 15x17 SS prop on it right now. There is a 160*F thremostat in now and at 4000rps I'm running around 170 - 180*F. There's also fresh bottom paint. I don't even know where to begin to look to fixing this. Is this a carb adjustment thing?

Help!

(Rick, are you out there...?!?!?!)

Chiliando · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

You sure you don't have a spun hub?

9mph can't be right.

Thad · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

Chiliando said:
You sure you don't have a spun hub?

9mph can't be right.

That's what I'm thinking.

What does the engine rev up to total?
At what rpm do you hit nine? If you trim down and gun it, do the rpm's jump before the boat?

You got something definitely not right.

witenite0560 · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

Is the dock still attached?? Sorry, couldn't help myself. Gotta be a spun prop or sheared shaft, if it's running good and making 4000 rpm.

lekmedm · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

Chiliando said:
You sure you don't have a spun hub?

9mph can't be right.

How would I know? Would the prop spin freely in that case?

QC · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

You need to mark the prop across the inner hub to the outer ring with the blades. Scribe somehow, run the boat, if the lines don't match up after you run her you have a spun hub (good thing in this case). If they are still aligned, then you either have a spun coupler between the engine and drive or something internally wrong with the drive. I would not suspect something internal as you would not typically make 1 MPH let alone 9 . . .

lekmedm · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

When we're talking hubs in this case, are we talking about the prop itself? There is no insert within the prop. It is one piece inside and just has the splines that fit over the spinning thingy.

QC · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

They are almost always two pieces, in your case I seriously hope so . . . They are usually pressed together tightly with a rubber "ring" in between.

Bondo · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

When we're talking hubs in this case, are we talking about the prop itself? There is no insert within the prop. It is one piece inside and just has the splines that fit over the spinning thingy

Ayuh,... But it's 2 different materials that can become Internally seperated...
As noted, Mark it, Run it, Check it...

lekmedm · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

I have a replacement prop that's aluminum. Maybe I should switch them out...?

QC · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

Yes, that would be good too . . . process of elimination.

lekmedm · Sep 3, 2009

Re: only 9mph @ 4000rpm !!!

witenite0560 said:
Is the dock still attached?? Sorry, couldn't help myself.

Hehehehe... good one... Of course, at the dock I'm running at idle. It's out on open water that I'm up at 4000rpm. (Just to be clear.)

I'll swap out the prop this weekend. It should be nice out here in New Jersey.

Chiliando · Sep 4, 2009

Re: only 9mph @ 4000rpm !!!

Let us know how the results of the Prop swap.

78ImperialT · Sep 4, 2009

Re: only 9mph @ 4000rpm !!!

maybe youll get lucky and it will work.

Jeep Man · Sep 4, 2009

Re: only 9mph @ 4000rpm !!!

lekmedm said:
I have a replacement prop that's aluminum. Maybe I should switch them out...?

Shut off motor before changing prop. hehehe

EddiePetty · Sep 4, 2009

Re: only 9mph @ 4000rpm !!!

......been bitin' my tongue since the initial post !!!!

You DID take the boat off the trailer...didn't you.

Just Ed

HappierWet · Sep 4, 2009

Re: only 9mph @ 4000rpm !!!

EddiePetty said:
......been bitin' my tongue since the initial post !!!!

You DID take the boat off the trailer...didn't you.

Just Ed

AND I thought he was draggin an anchor, I just didn't think it was quite that big.

Seriously, It's either the prop hub, or the coupler

.......OR it's really SERIOUS.

lekmedm · Sep 4, 2009

Re: only 9mph @ 4000rpm !!!

Takin' cheap shots at the newbie, eh...? Hehehehe... I know it's in good fun.

If I had my boat on a trailer, I would think my truck could tow it faster than 9mph!

The anchor I'm dragging is my enthusiasm for this boat.

...and Jeep Man, as one Jeep guy to another, that "shut off the motor" shot was low! I may be stupid, but I ain't dumb!

LIQUID PROZAC · Sep 4, 2009

Re: only 9mph @ 4000rpm !!!

good sense of humor lekmedm--let us know how it turns out

RickJ6956 · Sep 5, 2009

Re: only 9mph @ 4000rpm !!!

I've had two boats that had the same symptoms: The engines revs, but the boat doesn't go.

My 20-foot Four Winns spun a prop. With the boat on the trailer, battery disconnected, and the drive in gear, I was able to spin the prop fins by hand without moving the inside hub or shaft. Took it to a prop shop. They fixed it for about $60.

The 25-foot Larson spun a coupler. The coupler is bolted to the flywheel at the rear of the engine. This is where the transfer of power takes place between the engine and outdrive. In many boats the spline (shaft) that comes from the drive is exposed -- like the driveshaft in a car where it connects to the transmission.

Look for signs of a spun coupler: Metal filings or rubber filings under the point at which the spline enters the flywheel cover. Get your head down there and use a flashlight and mirror.

A spun prop is an easy fix. Pull it and send it to a prop shop for R/R.

A spun coupler requires pulling the drive and the engine. It's a do-it-yourself project if you're mechanically inclined. You'll save at least $1,000.

only 9mph @ 4000rpm !!!

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