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Old 11-10-2016, 07:15 AM   #21
ranger42c's Avatar
City: Annapolis
Vessel Model: 58' Sedan Bridge
Join Date: Aug 2013
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Originally Posted by gaston View Post
Why not fit an electric motor to the prop shaft via pulley set up? seems a simple solution . Then just run the generator and use the battery bank ???

FWIW, our shaft seals depend on having the main engine running... for raw water lubrication...

That'd be a concern during towing, too, or when running under completely separate aux power (like an outboard), if OTW speed got too high... although at least the shafts can theoretically be locked in place temporarily so no rotation and therefore no need for raw water lube.


Chesapeake Bay, USA
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Old 12-19-2016, 12:24 AM   #22
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City: Kenmore
Vessel Name: Snapdragon
Vessel Model: Seakeeper 41'
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This is an little bit of an old thread, but if you are still considering this, my 2 cents is... All the people saying this will never work have obviously never used a system like this. While much smaller, my last boat was a 28' overall aluminum fishing boat that had a 15hp trolling motor that we used extensively for fishing. We used that motor in all kinds of horrible conditions, and never even got close to having the throttle pinned. Our biggest problem was that we would fish for hours, and the alternator didn't put out enough amps at low rpm's to feed all our electronics, autopilot, etc. We used it to backtroll into huge waves 40 miles offshore at Westport WA while halibut fishing and had multiple waves completely submerge the motor in green water. It never so much a hiccuped. I used it once in reverse, to pull us off a lee shore beach (We were on the gravel with large white caps pounding on us) in a horrible storm after we had fouled the main with a dock line in a disastrous boat ramp debacle.

I had an extra long shaft 15hp Honda, and it was mounted low. I used it many times in horrendous conditions, and it never once pulled out of the water or had cavitation issues. I think one of the first pleasure boat to cross the Atlantic way back when, had something like a 10hp gasoline engine. I would get a 15hp as they are similar price, and have better alternators, more power. The other aspect I liked, was that if you ever killed your batteries, you had an engine you could hand start, and with a little patience, charge your batteries enough to get the main started. The biggest problem you will have is figuring out Gasoline storage, and running it often enough so that when you go to use it, it isn't full of bad gas. Also it helps if the motor has a hose connection for flushing fresh water built into it, as the earmuff type flushers are a pain if the boat is in the water.

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Old 12-23-2016, 11:31 PM   #23
Join Date: Apr 2014
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I did it for several years on a 40 ft Pilgrim trawler using a long shaft sail drive with a big low pitch prop. I had a flat SS mounting plate with a slide in motor mount. the motor was other wise used for my 13 ft aluminum utility boat on the roof. A block and tackle attached to the overhead roof was used to lower motor onto its bracket. My 24000lb boat called for 24 HP by my fuzzy memory for hull sped. IN quiet water 4K never had the misfortune to need it in waves. On my 15000lb 38 ft True North a long shaft 10 hp sail drive mounted aft easily attained 4-5K also in quiet water. I doubt that either set up would work in snotty conditions but it is doable on certain boats.

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