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Old 12-01-2016, 19:58   #1
er9
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Would 4hp outboard push 36' monohull?

I'm looking at a 4hp outboard as a way to get my sailboat in and out of the slip/marina temporarily. engine is not running so i need to be able to leave slip and motor just far enough to raise sails. also will need it to return.

im considering a 4hp or 6hp. cost is an issue thats why i'm considering the cheaper 4hp. it would eventually just be a dinghy motor/emergency backup. for now i just need something mounted to the transom as a temporary engine.

do you think a 4hp outboard on the transom would be powerfull enough to move a 16,000lb boat? obviously dont need to go very fast just be able to keep it under control in the protected channel.
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Old 12-01-2016, 20:03   #2
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Re: Would 4hp outboard push 36' monohull?

In calm conditions it would do ok, but if the wind should get up whilst under way, I doubt if 4 or even 6 hp would push to windward very well... and if it is choppy, the motor would quite likely come out of the water regularly.

We've moved big boats with our dinghy many times. OUrs have been 15 hp dinghies, but we've seen others doing it with very small motors.

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Old 13-01-2016, 00:16   #3
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Re: Would 4hp outboard push 36' monohull?

I moved our 17 ton 42 footer the other day using a hip tie and a 3.5 HP Tohatsu on our 8 foot dink.


I say moved.


I did not say controlled.


Personally, I would reckon that you would be asking for trouble. If the wind comes up unexpectedly you are in a difficult position. There just isn't the grip that you would need, aside from anything else.


I used to take Dad's 4.5 ton 27 foot Van De Stat out with an 8HP on the back, and that was stressful enough, even in good conditions.


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Old 13-01-2016, 06:02   #4
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Re: Would 4hp outboard push 36' monohull?

We had our engine go out in the ICW 15 miles from the nearest civilization.
The 5hp dink engine on the hip got us where we needed to go, but I'd not want to do that just for the sake of sailing. Getting into the marina was almost a catastrophe. We weigh in at 15000 lbs empty.


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Old 13-01-2016, 06:31   #5
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Re: Would 4hp outboard push 36' monohull?

Hip-towed my 35', 12,000 sailboat with a 6 hp on 10' inflatable for several miles...similar experience to others, would not want to use it to repeatedly dock, just not enough power. A 9.9 or better. Most small outboards don't get a huge amount of usage hours, I would look at finding a well maintained used motor if cost is an issue.
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Old 13-01-2016, 06:37   #6
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Re: Would 4hp outboard push 36' monohull?

any smaller outboard meant to push a small boat along at a decent clip, just isn't going to provide much thrust. So I guess I'm saying even a 9.9 won't work very well, but a 4 or a 6 will work, just have to use your brain, your not shooting into the slip at a good clip to pop her into reverse and stop, nor turn quickly etc.
But I believe if you use your brain, you will be surprised at how well it will work, it will actually push you along at a good clip, just will take forever to overcome the inertia of the boat. In other words you can almost run it wide open and count to ten before the boat even begins to move, but leave it there for 4 or 5 minutes and you will be moving surprisingly fast, there is speed, but almost no thrust if that makes sense.

On edit, if you do do it, back to use your brain, if the wind is up, throw a hook and dinghy in and come back when its down to go into the marina.
That is what I do even with my main engine working fine, I don't try to dock with a high crosswind, takes all the fun out of it.
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Old 13-01-2016, 09:34   #7
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Re: Would 4hp outboard push 36' monohull?

Sounds like your plan is to put the outboard on the transom. the examples for hip-towed sound like a two person operation - one on the dinghy, one on the boat you are moving.
I'd suggest 9.9 hp minimum if you are going to do this single handed.
Also like the safe plan of anchor, dinghy in and come back when winds die down.
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Old 13-01-2016, 09:34   #8
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Re: Would 4hp outboard push 36' monohull?

Quote:
Originally Posted by er9 View Post
...engine is not running...
Repair the engine. A 36' boat needs about 25 hp. Don't screw up the boat with an outboard.
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Old 13-01-2016, 09:41   #9
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Re: Would 4hp outboard push 36' monohull?

We were out on the SeaHawk off Naples New Years Day, lost battier to start engine so capt Matt brought her into dock under sail using westerly we had that day! Quite proud of that effort!
As for moving these small yachts with strap on engines, get ready to bounce off things once in awhile! Usually at low speeds nothing is too damaged except your pride! But hey, crow is ok to eat now and then! It's also ok to ask for HELP!
Peace and happy cruising!
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Old 13-01-2016, 09:50   #10
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Re: Would 4hp outboard push 36' monohull?

In a pinch, judicious and temporary, particularly if you are picking the conditions prudently, it will work. I have used a 5HP to maneuver a 43 footer. Would strongly recommend against it being a long term arrangement when you might get caught in unfavorable circumstances. It narrows your margin of safety.
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Old 13-01-2016, 10:09   #11
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Re: Would 4hp outboard push 36' monohull?

I seem to recall Tom Cunliffe did an article in Yachting Monthly (UK magazine) about a year back about using a 2.5hp outboard on a dinghy using an alongside tow, to move a 35 footer, If I remember correctly, they were able to make about 1.5~2 knots, so a 4hp would probably achieve 3 knots at least.
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Old 13-01-2016, 10:37   #12
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Re: Would 4hp outboard push 36' monohull?

4hp No
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Old 13-01-2016, 10:41   #13
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Re: Would 4hp outboard push 36' monohull?

This is a fairly simple engineering problem of force needed and forced applied. flat water, no wind, no current, then the only force to overcome is inertia and your engine can do that. Wind picks up to 5 knots or current goes to 2 knots and then your in equilibrium. 10 knots of wind, or 5 knots of current and your screwed. Other issue is stopping. Once you get your titanic in motion, your engine will not be able to stop it. All this assumes no waves. Any kind of wave action above 4 feet and you are going nowhere.
None of this has to do with control of the boat. Steering will be iffy at best, turning radii will be huge, and hopefully you have enough boat insurance to cover the damages to other boats you are likely to cause.
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Old 13-01-2016, 10:47   #14
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Re: Would 4hp outboard push 36' monohull?

(semi) Ideally you'd want an at least 8-10 hp "high-thrust" outboard for a boat that size. But if you are going with a 4-6 hp outboard, I'd really try and find one of the high-thrust models.

Tohatsu have the 6hp "SailPro" and Mercury also sell a 5hp high thrust outboard from memory.

Most of the difference (at least in the 5-6 hp range) compared to regular outboards is the prop. So fitting an after-market "high-thrust" prop to a standard (preferably long-shaft) outboard could also work, not sure how easy it is to find one for such a small motor thought/

You might also be able to find an old Chrysler "Sailor" 180 (7.5hp) or 250 (10 hp) two stroke outboard for not too much money.
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Old 13-01-2016, 11:08   #15
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Re: Would 4hp outboard push 36' monohull?

Quote:
Originally Posted by er9 View Post
I'm looking at a 4hp outboard as a way to get my sailboat in and out of the slip/marina temporarily. engine is not running so i need to be able to leave slip and motor just far enough to raise sails. also will need it to return.

im considering a 4hp or 6hp. cost is an issue thats why i'm considering the cheaper 4hp. it would eventually just be a dinghy motor/emergency backup. for now i just need something mounted to the transom as a temporary engine.

do you think a 4hp outboard on the transom would be powerfull enough to move a 16,000lb boat? obviously dont need to go very fast just be able to keep it under control in the protected channel.

I used to tow my 15,000 lb. 35' Cheoy Lion with a 1.2 HP Sears Gamefisher using the dinghy but we used sailed 99% of the time. Obviously a larger engine would be better but in reality if you are not in a hurry it does not take much to move a sailboat around. Lin and Larry Pardey have moved their two engineless world cruising boats around using a sweep, no engine at all. The windage of your boat will be more of a factor than the weight btw. Just carefully select good conditions when you go out sailing and you will be fine with the 4 hp but consider mounting it on your dinghy instead of the transom of your sailboat. Look into getting a lower pitch prop of the largest diameter that will fit your engine to get the best thrust. Especially if have an inflatable you can easily push the bow, stern or whatever as needed to ease your boat back into the slip. You can lash the dinghy alongside the stern and steer from your sailboat if you are going a ways. Best of luck. James
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