Minumum HP

[andrewkafp]

What would be the MINIMUM HP for a small emergency Auxiliary or trolling petrol motor which would move a 4.5 metre 15-16ft Half cabin boat ?<br />Are we talking 2HP or more like 4-5 ???

 

[ledgefinder]

Re: Minumum HP

We move a 19' cuddy cabin sailboat just fine with an Evinrude 3hp. Might be able to get away with a little less. I recommend you steer clear of the "Cruise&Carry" brand, by the way. They have much less displacement, so get their horsepower by being more highly-tuned. That makes their power delivery 'peaky', so if you're in waves the motor screams then bogs instead of quietly pulling along.

 

[JB]

Re: Minumum HP

G'day, Andrew.<br /><br />While a 2-4hp "kicker" will slow troll your boat in still water, I don't think it would be adequate as an auxiliary if you have currents, rough water or winds to deal with.<br /><br />I had a 2HP kicker on my 17' CenterConsole and it wouldn't do the job in even mildly rough conditions.<br /><br />I would suggest 6 to 10hp.<br /><br />Good luck.

 

[ledgefinder]

Re: Minumum HP

I'd have to respectfully disagree with JB. <br /><br />Sailboats in the 26' 3000lb range use 6-10hp as serious auxiliary power - you can go hull speed with them (~6-7 knots) without full throttle, & make good time even with a headwind & adverse current. <br /><br />In the 1960s, it was common to use the 3hp OMCs on 25' - & I believe that's still the case today in many places worldwide. I don't know if it's a question of how they're propped, or if you need a displacement hull (maybe planing hulls get blown around more), but even in a 20knot wind we do fine with the 3hp - running it at about 1/2 throttle is plenty.<br /><br />I always thought the 2-cylinder 3hp OMCs were sort of over-designed, it may be that the 2hp have a good bit less pulling torque (though propped right things should be equal?).

 

[Forktail]

Re: Minumum HP

ledgefinder, Johnson no longer makes a twin-cylinder under 6 hp (and Evinrude makes nothing smaller than a 75 hp). Suggesting that a 3 hp running at 1/2 throttle in 20 knot winds would be adequate, is rediculous and borderline unsafe. This is a 16' boat with a cabin.<br /><br />A 2-4 hp isn't going to cut it. Mainly because most are 1-cylinder and of lesser durability. It's not until 6-8 hp that you get the more durable 2-cylinder models. In times of dire need, you won't be sorry you spent a few bucks more.

 

[G DANE]

Re: Minumum HP

H andrewkafp<br /><br />At a time when I was rebuilding my 35 HP, I borrowed a 6HP Evinrude Fisherman model from late 70 ties from my brotherinlaw. It ran good and moved the boat fine, even in rough water. However having tried this I would not recomment anything less at all. I you can get a good running 6 HP fisherman or 9.9 even elder ones, you will have a GREAT motor with few problems. These really last.

 

[Boatist]

Re: Minumum HP

Andrewkafp<br />I can tell you this I have a 21 foot Aluminum boat and have a 15 hp Johnson with a high thrust prop and when I replace will go with at least a 20. It is true Sail boat rarely use over 9.9HP but they are hulls designed to slip thru the water with wind power only. If you only use boat on protected small lakes 8HP might work, but if you go into river with current or big lakes where have wind and wave I would go with at least a 9.9. Both the 9.9 and 15 HP Johnson/Evinrude 1974 and later use same power head and weigh 74 LB. For my boat will still slow down so slow lures will not work. On windy days I have trouble turning into the wind or day with big swells have trouble turning into the swells. Sailboats have a big keel that stops wind or waves from moving bow sideways. Power boats have very little keel so motor must have enough power to push stern of boat sideways faster than wind can push the bow. If your motor does not have enough power to do that then you can not turn into the wind or waves.

 

[ledgefinder]

Re: Minumum HP

Forktail, I'm not suggesting a 3hp is enough - I am telling you it is. We've used this motor on sailboats up to 26' over the years, in plenty of heavy weather. There are similar rigs all over on the Maine coast. Never wanted more - when the 3hp isn't around, I clamp on a less-powerful British Seagull.<br /><br />Sounds like there's more to it than just horsepower and boat length, and more factors involved. Boatist's comments on keeping a heading sound like he/she might be dead on. I'm guessing a key factor is the tendency of the hull to get steered around by the wind, versus the helm. A big dory is easy to handle on a windy day, ferrying people out to a mooring - while on the same day two paddlers can't keep a canoe going because it keeps trying to turn off the wind. <br /><br />Have to admit I've hardly ever run the 3hp on a big powerboat. When I had a 19' GradyWhite speedboat, I strapped the Seagull up under the foredeck as an 'emergency backup'. Forktail, your're right it might not have worked out for me when I needed it. It ran it each summer to test it & go through the procedure, but never tried it in heavy weather.

 

[JB]

Re: Minumum HP

Ledgefinder.<br /><br />What it takes to move/control a sailing, or other slick displacement hull is not even in the same universe with what it takes to do the same for a planing hull. <br /><br />A JohnnyRude 3 hp twin will move and control most sailing hulls under 35'. A paddle will do wonderful things with a 17' canoe, but don't expect either to do well on a 16' half cabin planing hull.<br /><br />I agree with Forktail, and for the reasons he states.

 

[slow_boat]

Re: Minumum HP

Forktail & JB et al are dead on about planing hulls. I have been on fair size lakes in 20-25 mph wind when I needed all my 10hp had to offer just to turn a 16' aluminum boat against the wind & keep it on course. Same in river current. Guides in Alaska frequently use 25+ hp on small aluminum v-hulls & skiffs so they can power out of eddies that would capture (or worse) a lesser powered boat. Sailboats are a completely different beast & require little power to move them.

 

[Forktail]

Re: Minumum HP

This morning I took a look at all the 20-26' sailers down at the harbor.<br /><br />I didn't see any with a 2, 3, 4, 5, or 6 hp outboard kicker. Almost all had an extra long shaft, high-thrust, twin-cylinder, 9.9 hp.

 

[andrewkafp]

Re: Minumum HP

But we're only talking a 15ft fibreglass halfcab with 2 people aboard in a bay not open sea.

 

[andrewkafp]

Re: Minumum HP

Well I ended up with a 6HP Suzuki twin in very good condition. Most boats being launched at out ramp have similar motors.

 

[roscoe]

Re: Minumum HP

enjoy