brianhughes
New member
i have fitted a 60hp yamaha engine to a 18' mayland goes well upto 30mph then the boat starts bouncing even on flat seas.is this normal. if not can anything be done to stop this happening
boat engine
- Thread starter brianhughes
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duncan
Active member
Not quite sure of the reason for my learned friends' responses to you ?
I suspect that you are experiencing porpoising as the boat is right at the top of it's performance and the relationship between the hull's hydronamic lift , the engines angle of thrust and the weight distribution go through a cycle - with first one then another dominating.
Simply trimming the engine in a little should stabilise things.
30mph is right at the top end for this combination I would have thought.
I suspect that you are experiencing porpoising as the boat is right at the top of it's performance and the relationship between the hull's hydronamic lift , the engines angle of thrust and the weight distribution go through a cycle - with first one then another dominating.
Simply trimming the engine in a little should stabilise things.
30mph is right at the top end for this combination I would have thought.
brianrunyard
New member
\"Porpoising\" Ignore the attempts at humour
Ignore all the ignorant smart alec replies. Presumably they know it all and never need to ask any questions!
Sounds as though you're porpoising.
Porpoising is when a boat is on plane in realtively smooth water and the bow continues to go up and down.
Try timming your engine in a little.
Ignore all the ignorant smart alec replies. Presumably they know it all and never need to ask any questions!
Sounds as though you're porpoising.
Porpoising is when a boat is on plane in realtively smooth water and the bow continues to go up and down.
Try timming your engine in a little.
Its_Only_Money
New member
Welcome - I used to have a Yamaha 90hp on the back of a Picton 18ft Mardigras so no issues with 60hp on 18ft per se but it sounds like she is trimmed too high - is the 60hp electric trim?? If so then trim down and see if the situation improves. If not then it would be worth experimenting by dropping the fixed trim point to a better (lower compromise). Sometimes if the trim is marginal then a swell will keep you porpoising even if she wouldn't in flat water at the same speed/trim.
Oh and the speedo's can be way out, what revs are you pulling when the porpoising starts?
PM me if you like a longer chat about it without the crap comments from the afflicted.
Oh and the speedo's can be way out, what revs are you pulling when the porpoising starts?
PM me if you like a longer chat about it without the crap comments from the afflicted.
Lakesailor
New member
I think the MOBO forum is running some threads on porpoising at the moment and there is someone asking about max HP for a Mayland.
Some people do look at other fora. It helps make them more rounded people.
Some people do look at other fora. It helps make them more rounded people.
Colvic Watson
Well-known member
Apologies if any offense was caused, just a bit of harmless ribbing (is that a pun?). But it's interesting to see how nothing gets us all worked up as much as sail boaties having a go at MOBO's or vice versa.
Sybarite
Well-known member
Welcome to the forum and sorry that you have been subjected to some idiotic puerile comments I'm not competent to advise you but trim does seem to be the key.
John
John
