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Old 12 March 2009, 17:45   #1
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Under tow - engine up or down..?

The earlier thread reminded me of an incident where we had a gearbox go bang and were towed back at 10(ish)knots for about 7 miles. The boat was then slipped, but did not go in for repair until a few months later. When it was checked the powerhead had seized as a result of water going up the exhaust whilst under tow.

Now, it was not my boat so I did not really have anything to do with the maintenance side, but I remember much moaning and griping about being stitched up at the time.

I don't actually know if this was the case (it certainly was a large repair bill) but it seemed a distinctly plausible possibility to me.

So, is it best to leave the engine up or down if being towed?

Just curious really...

t

PS. in case it is relevant, it was a 115hp v6 2/stk Yamaha o/board.
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Old 12 March 2009, 18:26   #2
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Engine up - less drag so faster towing.
Engine down - steering ability.
If you can get the boat to follow the towing boat safely and relaibly, then engine up.

Surprised there was a problem from being towed, but its never good to leave a boat sitting around after a problem. Whatever the cause may be.
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Old 12 March 2009, 19:24   #3
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How does water get forced up the exhaust when the exhaust on most outboards faces backwards?

When I have been toddling round on my 6hp aux to give it a run from time to time I usually put it in the straight ahead position (actually slightly off to one side to account for its offset) and use the main engine for steering, which is admittedly slower at about 4 knots typically but I've not had any sign of problems when restarting even after 30 min or so chugging along.
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Old 13 March 2009, 15:19   #4
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Quote:
Originally Posted by BogMonster View Post
How does water get forced up the exhaust when the exhaust on most outboards faces backwards?
Yes I'd agree with that. Have certainly heard of water getting into cylinder with an agressive launch but not towing.

Makes approx .3 knott diff on mine with engine up / down when running on 6hp aux but with main engine down it's much more placid and doesn't dart about in the waves. I'd vote for down!
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Old 15 March 2009, 06:38   #5
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Think part of the trouble here is the time from the original engine failure to when the repair was carried out. For obvious reasons - you would normally flush the engine out after use. As this hasn't happened any seawater in the powerhead cooling passages has dried out leaving salt deposits, effectively seizing the engine.

Worse case scenario would be to remove the lower leg, then spray fogging oil or WD40 into the sparkplug bores. If possible - to manually turn the engine over (without starting) to lubricate the cylinders.

Ideally get the engine repaired within a week, then allow it to run in fresh water (with muffs or in a tank) for at least 30 minutes.
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Old 15 March 2009, 07:07   #6
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Quote:
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Makes approx .3 knott diff on mine with engine up / down when running on 6hp aux but with main engine down it's much more placid and doesn't dart about in the waves. I'd vote for down!
I find chugging along on the aux that the directional stability of the boat is much better with the main engine down, using just the aux it seems very twitchy and prone to over-correcting. Partly due to the fact I am not used to tiller steer perhaps but I much prefer to stick it straight ahead and sit at the sharp end
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