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yorkey
05-31-2005, 11:47 PM
I have a 1993 22' Classic with the 454 OMC King Cobra combination and I'm running an aluminum 14 1/4 X 21 (not an aftermarket one though, this one has thicker blades then the real cheap ones).

If I decide to get a little cocky jumping off swells at the lake (little fresh water swells, not the ocean), I'll pump the throttle between swells for more fun (rpm's are only in the 3500-3900 range I would say). All of a sudden it feels like the drive slips or something and the engine just revs and it sounds like the engine "sputters" when this happens. If I back off and smoothly accelerate again I am back in gear and everything seems to be just fine.

Please, someone tell me that this could be something simple that's not a bad lower unit or something... please! I don't want to just cruise; I want to ride this Thoroughbred just a little...

Brian Main
06-01-2005, 12:39 AM
Hey,

I'd go for the easy stuff first. Check for a loose cable at the linkage block on the exhaust riser. My guess is that one of them has come loose so that the transmission doesn't engage and the interupter is activated.

It might be wishful thinking but it could be a simple fix.

Good luck!

Brian.

Lenny
06-01-2005, 12:53 AM
Are you sure you are not just cavitating? I can do that and it is not the Outboard "LOUD" thing we are all used to... it is actually quite quiet, just slipping.

:confused:

Brian Main
06-01-2005, 01:03 AM
On second thought I like Lenny's explanation better. I guess it would depend on how much thottle you are giving it when you "pump the throttle" between the swells.

BUIZILLA
06-01-2005, 06:39 AM
why the cheapy prop??

i'd say prop hub....

JH

MOP
06-01-2005, 07:41 AM
You pumping the throttle during the jump I feel is putting to much gas into the engine when you really should be throttling back, the engine can't quite burn the extra gas so it sputters until it catches back on. That also puts a lot of load on the entire drive train, you are going to break it trying for a thrill.

Phil

blackhawk
06-01-2005, 09:17 AM
Phil, I think he is saying that he is giving it throttle between the jumping of swells, like accelerating between them. At least I hope that's what he is saying!

Like BUIZILLA said, could be a prop hub.

MOP
06-01-2005, 09:33 AM
Phil, I think he is saying that he is giving it throttle between the jumping of swells, like accelerating between them. At least I hope that's what he is saying!

Like BUIZILLA said, could be a prop hub.

I doubt the hub as he says it runs fine afterwards, when a hub or coupler goes it is gone but many times you can limp back to the dock at low speed. But in thinking about it a little more I have a hunch the cone in the drive is starting to go, by whaling on the gas he has to be putting a lot of undo strain on his rig.

Phil

RedDog
06-01-2005, 09:57 AM
I'd say cavitation due to the use of an aluminum prop. Borrow a 21 or 22 inch stainless prop and see if your problems are gone.

yorkey
06-01-2005, 10:44 AM
Hi guys, thank you for the input thus far. Yes, I mean that I am accelerating in between swells. I was using an aluminum prop because I was still feeling like a novice because last season I was in shallow water in a cove and accidentally hit the sand and was thankful that it was a cheap prop at that time because a blade chipped as opposed to worse. I told myself that I needed to go one full season without ever doing that again before I'd trust myself with a stainless (I don't want to damage my drive). BUT, maybe I need to just step up and be more careful with it if my performance will be better.

Speaking of being a novice, what do you mean by experiencing cavitation?

I'm not happy in general anyway because with this configuration I've been told not to exceed 4400RPM and I'm barely hitting 60MPH, I'd like to pick that up a little bit on the top end speed.

If I accelarate full throttle from a dead stop and cruise at 60MPH, I never have a problem with this slipping effect, only when I get a little more aggressive on the swells. I should be able to get a little more aggressive though, shouldn't I?

mrfixxall
06-01-2005, 10:45 AM
I agree with pop do you have a solid hub in your prop or rubber,, i would ck their before i ck the coupler....

RedDog
06-01-2005, 11:43 AM
Cavitation is due to a low pressure region on the surface of the prop blade. This low pressure allows the water to boil-off, creating bubbles. The blade then spins through the bubbles - RPMs go up, slippage occurs. Aluminum prop plus high HP yields cavitation.

blackhawk
06-01-2005, 01:07 PM
Cavitation is due to a low pressure region on the surface of the prop blade. This low pressure allows the water to boil-off, creating bubbles. The blade then spins through the bubbles - RPMs go up, slippage occurs. Aluminum prop plus high HP yields cavitation.

Damn, learn somethin new everyday! I had no idea that's what caused cavitation. Thanks for the info.