2hp to 5hp tender outboard upgrade.

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scruff

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we currently have a 2.9m inflatable keel tender with a 13kg 2hp outboard. This trundles us along at a couple of knots, is easy to lift from car to tender, then tender to boat rail each time we sail and is generally fine.

I've seen a 2stroke, 5hp yamaha for sale locally. Internet recons to be 20kg. Would this engine get a our tender up on the plane with two adults?

I quite fancy having a larger range to explore when at anchor, and at present the summer and winter moorings are 7nm apart. Normally this necessitates two cars, one at each end. Having a larger range may make the logistics easier...

Thanks
 
I'd have thought that 10HP would be adequate to plane a 2.9m two-up, but I'm not sure. If so I highly recommend the Tohatsu 9.8 two-stroke.

You might also try the Facebook RIBs and SIBs group, which I've found very helpful.

The difference between displacement and planing is like night and day, and in my opinion a planing tender makes a huge difference for the kind of cruising I like to do - it enabled me to explore the Lorient roadstead and the Île De Groix; it makes it easy to commute from anchor to supermarket or to go and visit a store on the other side of town for automotive parts or a new laptop. 7 miles is no bother at all.
 
I have a Honwave T32 with Honda 5 hp. It will plane and acheive around 14 knots one up.

For 2 up planing I think 8 to 10 hp is required.

I'm looking at the new Mercury 15 efi which will make it fly!
 
Interesting as I have exactly the same situation and was planning 5hp on a 2.9m Zodiac inflatable floor. If that only gets me to hull speed then maybe I’m back to the original idea which was an electric outboard which has the significant benefit of not carrying petrol aboard. Or stick with the 2.5hp Mercury which will just about poodle along okay. I just I can’t countenance having to deal with a heavy 8hp engine in order to plane the dinghy, too heavy.
 
I have the AB 9VS with a 2 stroke Yamaha 8hp ( weight of engine is 28kg) engine is just about manageable but I wouldn't want any heaver. She will plane 2 up
 
Robih said:
Interesting as I have exactly the same situation and was planning 5hp on a 2.9m Zodiac inflatable floor. If that only gets me to hull speed then maybe I’m back to the original idea which was an electric outboard which has the significant benefit of not carrying petrol aboard. Or stick with the 2.5hp Mercury which will just about poodle along okay. I just I can’t countenance having to deal with a heavy 8hp engine in order to plane the dinghy, too heavy.
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Coming to a simiar conclusion. I recon 20kg would be fine to manual lift from tender into stern rail of the boat. Near 40kg for a 8hp is a different kettle of fish entirely
 
I got a new 3.5 tohat which planes with just me on my H27 airdeck. Nice engine.
It was a payoff with weight to hoist it on board. i can't deal with anything heavier and still heave it up (davit option noted)
If I put a decent heavy bag in the boat it does not plane.....!
maybe I need to eat more salads..................
 
KompetentKrew said:
I'd have thought that 10HP would be adequate to plane a 2.9m two-up, but I'm not sure. If so I highly recommend the Tohatsu 9.8 two-stroke. /........./ 7 miles is no bother at all.
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Thanks, that's good to know. I recon if I were going that size then I'd likely need to get davits to lift the whole tender and engine. Turns it from a £400 proposition to a £4,000 one...
 
cueball said:
I have the AB 9VS with a 2 stroke Yamaha 8hp ( weight of engine is 28kg) engine is just about manageable but I wouldn't want any heaver. She will plane 2 up
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OK, that is a bit lighter than I thought it would be. Do you lift by hand or have a outboard derek?
 
Used to lift a Tohatsu 3.5 onto the stern... made carry handles from rope tied around the top, not great in a chop from the tender. I did shove it up onto the stern pushpit bracket with me standing inthe tender but again it was not ideal, too heavy really. I am going to try a Honda 2.5 air cooled next time but it is not much lighter then a 3.5HP.
 
I've been thinking about much the same upgrade. We have somehow collected three different 2.5-3.5hp 2 strokes.
On our little Redcrest we hardly go above idle, you just get wetter and don't go all that much faster.
On our (heavy) 310 RIB you can go to full throttle but it's still pretty slow.
I'd like to try a slightly bigger o/b but I have a feeling that nothing magic will happen with a 4-6hp and it will just plough a little faster. Maybe plane one-up? Not enough benefit to be worth the extra cost, weight, and fuel consumption.
I would love a Tohatsu 9.8hp 2 stroke, but they are like hen's teeth, or you can buy one in Alderney for £1700 (ouch).

We plan to replace both tenders with a nesting plywood dinghy which will be lighter than the 310 and more easily driven... would that plane with a 6hp?
I think I will sell one of the little engines and buy a trolling motor. On this year's cruise, three weeks of daily dinghy use with the Redcrest, there was not a single moment where an electric motor would not have been preferable. Got to be worth a try. But I'd still want a bigger engine for planing performance on those odd occasions when it matters.
 
scruff said:
Thanks, that's good to know. I recon if I were going that size then I'd likely need to get davits to lift the whole tender and engine. Turns it from a £400 proposition to a £4,000 one...
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scruff said:
OK, that is a bit lighter than I thought it would be. Do you lift by hand or have a outboard derek?
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The Tohatsu is about 22kg, though - it really is the perfect engine IMO.

I have the dinghy on davits, but I take the engine off and lift it aboard separately. I'm tall but weedy, and singlehanded it's a bit cumbersome but manageable - it would be absolutely fine to handle for two people.

The Tohatsu 9.8 two-stroke is no longer sold in the EU due to emissions regulations, and I don't think our government has gotten around to scrapping those yet (write to your MP!), so it's quite sought after on the secondhand market. If you set a notification on Gumtree then you'll see a listing of one every week or two, and they come up on eBay at about the same rate.

I'm so pleased with mine that I would have replaced it with a brand new one, were it not for Alderney's quarantine this year. Mine is 20 years old and suffers a little from stiffness of the clamps and tilting mechanism if neglected.

These engines sell for about £700 or £800 secondhand, but you'll need to be sharp as they find buyers quickly.
 
Kelpie said:
I would love a Tohatsu 9.8hp 2 stroke, but they are like hen's teeth, or you can buy one in Alderney for £1700 (ouch).
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To be fair this is no more expensive than any other brand new 10HP outboard, is it?

It's certainly insignificantly more expensive than the four-stroke 9.8 that's replaced it in Tohatsu's European range (I can find that listed at £1600 and £1650).

I know that one is spoilt for choice on the secondhand market when it comes to any other model of petrol outboard, but this seems a fair price for a brand new engine.
 
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