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post #1 of 11 Old 07-23-2012 Thread Starter
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outboard in a chop

If you are running an outboard in a chop, and the prop starts coming out of the water for a few seconds at a time, is that harmful to the motor?
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post #2 of 11 Old 07-23-2012
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Lightbulb Re: outboard in a chop

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If you are running an outboard in a chop, and the prop starts coming out of the water for a few seconds at a time, is that harmful to the motor?
Not once in a while, but Yes, if it happens very much.
And then there's the obvious problem of going slow with the motor not putting any thrust into the water.

If it's a common problem, you need a lower-mount bracket, or, far more likely, a longer shaft (25") outboard.
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post #3 of 11 Old 07-23-2012
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Re: outboard in a chop

I had a Catalina 25 last year with a 9.9 merc outboard.
The prop was in the water just below the cavitation plate.
It popped out in rough water a lot just like you said.
I was told the cavitation plate should be several inches below the water.
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post #4 of 11 Old 07-23-2012
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Re: outboard in a chop

Some of the newer motors have rev limiters. You might check with the manufacturer to see if yours has one? Tohatsu , maybe others, have a 25" shaft model. We have a 6HP, runs perfectly.

Tohatsu Outboard Motor 6hp 4-Stroke

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post #5 of 11 Old 07-23-2012
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Re: outboard in a chop

Quote:
Originally Posted by timangiel View Post
If you are running an outboard in a chop, and the prop starts coming out of the water for a few seconds at a time, is that harmful to the motor?
Even with a rev-limiter, you still really should throttle back each time the prop comes out of the water to avoid fatiguing (and eventually snapping) the shear-pin, which would be rather unfortunate if you were close to a lee shore at the time.

Having a long-shaft outboard would mean it should come out less.. but having the prop come out of the water each time you go over a big wave is just one of the disadvantages of using an outboard on the back of a yacht.

It's either something you learn to live with - or you get an inboard.

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"Honestly, I don't know why seamen persist in getting wrecked in some of the outlandish places they do, when they can do it in a nice place like Fiji." -- John Caldwell, "Desperate Voyage"
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post #6 of 11 Old 07-25-2012
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Re: outboard in a chop

Get your crew of sunbathers away from the bow and move them as far aft as possible/comfortable...that's about all you can do while it is happening.

'79 San Juan 7.7
Joe Pool Lake
DFW area TX
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post #7 of 11 Old 07-25-2012
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Re: outboard in a chop

Over the long run it will probably shorten the life of the engine some, but if it's an intermittent thing it probably doesn't hurt it much as long as you're not at full throttle. When the prob comes out of the water the cooling water intake also comes out of the water and then the prop hits the water again at high rpm and puts the engine under a huge load right when there is no water. Over a prolonged time the engine probably runs hotter than normal. The prop is also prone to spinning in the hub when this happens too, which will leave you with very little propulsion if it gets bad enough.

John
SV Laurie Anne

1988 Brewer 40 Pilothouse

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post #8 of 11 Old 07-25-2012
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Re: outboard in a chop

Overall, rev limiter or not, it is not a good thing. Besides sounding scary you are losing your thrust. I used to see this happen very often on San Francisco Bay. Not good if you are trying to beat off of a lee shore or other bad places. Suggest, that if possible, you lower your mount or as mentioned earlier, get a longer shaft motor.

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post #9 of 11 Old 07-25-2012
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Re: outboard in a chop

If you have sea room, you can alter course and motor downwind. The waves will then be overtaking the boat from astern, keeping the prop immersed as it slides down the face of one wave, as well as when it climbs the face of the wave ahead. You might not arrive at your destination at the time planned, but you might save damage to the engine. Cavitation happens mostly when motoring to windward, against the waves.
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post #10 of 11 Old 07-25-2012
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Re: outboard in a chop

ive found out that going side ways to the waves, Helps the motor always stay in the water in rough conditons bad to keep the boat like that when really rought but best way to go when just a small to medium chop.

16' mistral sailboat, And 27' coronado
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