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Old 25 February 2022, 11:27   #1
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Country: Thailand
Town: Hua Hin
Boat name: Yamaha 480R
Make: Yamaha
Length: 4m +
Engine: Honda 60hp 4 stroke
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Yamaha 480R

I've recently bought a 2nd hand Yamaha 480R rib with a Honda 60hp outboard. When I test drove it in flat water it was fine, but when I got it back to my sailing club in waves the bow rears up alarmingly. To get the boat flat I have to go fast enough to take off which is extremely uncomfortable. I'm worried the engine at 120kgs is too heavy for the boat. If so can anyone suggest how I can get it to ride waves more smoothly, like my old Far East 480 with 40hp Yamaha 2 stroke. Thanks in advance.
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Old 25 February 2022, 13:06   #2
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Country: UK - England
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Hi Rich and welcome to the forum!
What does the spec plate say about engine weight?

Probably within spec for 60hp but maybe not for 120kg. The Honda's maybe a little lardy as Yamaha's F70 is lighter I think.

First I think you need to make sure your engine is mounted as high as possible without the prop ventilating. Common sense to start here.

If the engine height's optimal and you can't compensate by trimming down then you could consider a Doel Fin. Following advice I tried my stern heavy boat (same length) without it but only for one outing as it made a huge difference, even at displacement.

Is there any weight you can move forward like the fuel tank? Maybe you could even move the console and seat forward to balance it out but that's a little extreme.
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Old 25 February 2022, 17:22   #3
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Thereís a few bits to look at. Firstly apologies if your more experienced than it appears but how are you operating trim i.e. what are you doing when. Also as above Honda well known for being reliable but heavy. Stick some
Heavy stuff in the front locker if you have one. Anchors/ chain/ water bottles/ unwanted children. See if it helps
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Old 26 February 2022, 05:33   #4
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Country: Australia
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Similar issue with my boat. Lightweight 4.5m aluminium RIB with a Honda 50hp.

Heavy fuel tank in the front locker by itself wasn't quite enough, and consequently wound up installing smart tabs (the spring loaded trim tabs), which made a world of difference. Engine is also trimmed all the way down. Hole shot is much improved, and planes much quicker and at lower speed.

The only remaining is that the boat wants to nose up at 8 knots - lower, or faster, it's fine. However, the only time I travel that speed is cruising in the river (speed limits), and placing some passengers forward counterbalances it nicely.

TL/DR: Weight in the front and tabs or a dolphin.
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Old 26 February 2022, 15:05   #5
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Country: Thailand
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Boat name: Yamaha 480R
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Thanks guys. The engine seems to be the right height. It has trim tabs fitted and today we lowered them a couple of cms. I put 12 kgs of chain the front locker which didn't seem to make much difference. But haven't had a chance to try the new trim tabs. I'm going to put 25kgs sand bag in front locker and will try tomorrow. But today in the waves we went out in my old Far East with the 40hp and it handled the waves impeccably. Let's see what happens tomorrow with the lower tabs and an extra 25kgs in the front.
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Old 26 February 2022, 16:03   #6
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Yeah, should note I went from a 25l tank in the stern to nearly 60 litres in the front locker, and it wasn't enough to make a noticeable difference, so I think you'd need a stupendous amount of weight to make it work with weight alone.
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Old 27 February 2022, 06:22   #7
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Country: Thailand
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https://linksharing.samsungcloud.com/utKYD4oAeB2g[/IMG]

This little clip gives an idea of what I'm up against.
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Old 27 February 2022, 09:39   #8
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Quote:
Originally Posted by Richard Hua Hin View Post
I've recently bought a 2nd hand Yamaha 480R rib with a Honda 60hp outboard. When I test drove it in flat water it was fine, but when I got it back to my sailing club in waves the bow rears up alarmingly. To get the boat flat I have to go fast enough to take off which is extremely uncomfortable. I'm worried the engine at 120kgs is too heavy for the boat. If so can anyone suggest how I can get it to ride waves more smoothly, like my old Far East 480 with 40hp Yamaha 2 stroke. Thanks in advance.

480R Fixed link


Ok similar problem to smaller Brig and Grand RIBs, there's a design compromise due to the huge forward deck area. The only solution is to move the console and seating forward if that's possible.

Trim tabs only work if there's a flow of hard water beneath them to push against. A hydrofoil which will work at displacement is a possible workaround but won't fix it. Forward ballast robs load capacity, sets the boat lower in the water and is another workaround.

Look at the 4.8 Ribcraft below, perfect example of balance - there's no forward deck area. This is where your console should be. With two adults on that bench you'd be even worse off. Tbh I don't think a lighter engine would help much either.
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Old 27 February 2022, 13:19   #9
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Country: Thailand
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Really helpful comments guys. WE've fixed the problem. Took the trim tabs down 3 cms both sides and put 25 kgs in the chain locker and the boat now behaves like a gent. I suspect that we could remove the 25 kgs as well and I'll try that tomorrow. I wouldn't have believed such a small adjustment to the tabs could have such a big impact, but what do I know, I'm just a sailor.
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Old 27 February 2022, 14:50   #10
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A good result!
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