How fast will a 10 hp motor push a 48 foot and 30,000 # sailboat?

[SecondBase]

Assume perfect day - no wind, no current, etc. for a one time transport of a number of miles prior to refit.

[NoahTreat]

I do not know the answer to your question. But I will tell you not all 10 hp motors are equal. Is it a 2 stroke or 4 stroke? How old is it? What kind of prop does it have. All things will determine your answer. Could mean the different between .5 know to 1 knot which would double your time

[Cheechako]

That's a heavy boat for sure. Are we talking a 42-45 ft boat? I'm not sure, but my guess is it will move it. It will take a while to get it going then chug along.... if the OB doesn't overheat.
Let's see.... a 10 HP on a dingy tied alongside a 12000 lb trawler would move it maybe 3.5 knots in flat water. (don't ask how I know!)

[SecondBase]

Thanks Noah, Cheechako. Yamaha 9.9 Four Stroke Remote with 20inch Long shaft with original Yamaha prop. Outboard is a couple years old and very good condition.

[Panope]

I get close to 5 knots with a 6 horse outboard and 15,000 lb. boat.

I'll guess that 10 hp and 30K lb will be similar.

Especially if the Yamaha is the "high thrust" model or it at least as a flat(ish) pitch prop.

Steve

[DougR]

My prop program says that a 10 h.p. inboard engine with a deep reduction ratio and an efficient prop will push that combination of length/ weight between 5 and 6 Kts in perfect conditions depending on what the water length is. 38-40' lwl goes 5 Kts, 48' lwl about 6 Kts.

Now that you are talking about an outboard engine with higher RPM, not so much gear reduction and less efficient prop I would have to guess somewhere around 4 Kts on a good day.

DougR

[Adelie]

Originally Posted by SecondBase

Assume perfect day - no wind, no current, etc. for a one time transport of a number of miles prior to refit.

LoA of 44'. What's LWL?

[puffcard]

3.5 kts my bet.

[SecondBase]

Originally Posted by Adelie

LoA of 44'. What's LWL?

40' waterline

[boatpoker]

$10 he can't pass 2 knots .... any takers ?

Slight breath of head wind ..... 1 knot.

[Calif.Ted]

I once tied a 2 hp Honda to a Catalina 270 to push it .5 NM across harbor after midnight in a drizzle and dead calm. It took a minute for the boat to start to move, then very slowly over .25 NM increased to maybe 3 kts. It was DEAD CALM, glassy slick, no wind. If you can extrapolate from there, I only tried it because I was so close to home after a LONG trip.
Freakin' injector pump on a Perkins picked that moment to pack it in.

[JPA Cate]

^^^^Yes, even small dinghy motors can move boats along quite well. Might take a while to overcome the initial inertia, but easily keep it moving.

I wouldn't want to do it terribly far, mind you, but I'll bet you can easily maintain the 4 kn. suggested above. Once moving, she'll want to keep moving. The faster she's going, the sooner you can cast her off and let the big boat coast into where she's going. For this reason, put the dock lines on first, placed so that people can easily help you get tied up, before you even start moving.

Ann

PS. Do NOT even think of using the dinghy to slow down the mother boat.

[Don C L]

2.85 knots.

[donradcliffe]

I hip-tied my dinghy to a 40 ft 25,000 lb sailboat and pushed it 5 miles into Hilo. Best I could do with my 18 hp outboard was 3 knots, but there was about 8 inches of grass on the hull of the sailboat.

My best guess would be 2.5 to 3 knots with a clean bottom and 10 hp.

[valhalla360]

I would guess somewhere on the order of 2.5-4.0kts.

Acceleration might take upwards of a minute or more. Not a big deal once on open water but it will be a total pig trying to dock.

Any adverse wind, waves or current and I wouldn't count on being able to make any headway.

As previously mentioned, the prop and reduction gear will make a big difference. A 10hp motor set up for a dingy that does 20kts will not do nearly as well as a low pitch prop on a high thrust motor set up for boats doing 6-8kts. It simply won't be able to spin up into the RPM range where it makes the rated HP. Also, being overloaded, you have to be careful of overheating the engine if it's more than getting to the other side of the harbor.

FYI - We had a bracket for our 5hp dingy outboard on a previous boat (34' Gemini Cat) on flat water, clam day, it topped out around 3kts.