Is it true that powerfull outboards can snap / crack transoms

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sshakespeare

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Chaps,
I'm looking to buy a fast fisher about 20 ft, not sure of inboard or outboard yet. Someone told me today to avoid outboards as the more powerful ones with a bit of grunt say 90Hp can crack and snap transoms, is this true? What do I need to look out for? Which brands should I avoid? /forums/images/graemlins/confused.gif
 
It is best to check with the boats manufacturer to find out what the maximum outboard size that can be fitted to the boat is. As long as the outboard that is fitted is within the maximum recommendation, then all 'should' be fine!

If an outboard that is too heavy or too powerful is fitted, then the transom can be damaged and subsequently weakened. Also, the boat will tend to sit in the water stern heavy, making it prone to riding 'bows up' when underway. In extreme circumstances flooding from the stern due to the outboard well being too close to the water line. Hope this helps! /forums/images/graemlins/smile.gif
 
ive seen boats with lowered transoms to allow short shaft instead of long shaft,
not been done well, let water in the transom woodwork between the inner and out fibreglass,
year later its roten, and then you have big problems
something easy to look out for
 
the new yamaha`s are quite good i have a 25hp one four stroke of course and it is brilliant. most of it is electronic though but experienced no problems with it. it is also very economical because i had a mercury 9.9hp two stroke and this 25hp now uses the same amount of petrol, i was amazed! recommend yamaha
 
If you follow the builders guidelines for wt and power, you should be fine. A modern fast fisher with outboard mountings has been designed to carry the engine correctly and safely - just make sure it is fitted properly. I have seen 20/21ftrs with 135s (optimax) on without a problem, but most seem to have 90s/110s. Go look around the Marinas you'll see plenty there (or there are in my area anyway!) Just don't try to install a Suzuki 300...!!!!!
 
Re: Is it true that powerful outboards can snap / crack transoms

Hi,

This happens mostly on older boats. Most speedboats/fast fishers over 5 years old have transoms that are basically Marine ply which is glassed in. Over time water leaks in and weakens it. Then someone sticks a big heavy powerful lump on the back and it rips the back off....

You should never overpower a boat either...though I often did!

paul /forums/images/graemlins/smile.gif
 
At sea, no. Even if you fit an outboard twice as big as the manufacturer's recommended, the boat will take off and lose control before the transom cracks. I've run 125hp on boats rated at max 85hp and they're fine, no cracks

But on a trailer it can be different. Trailer suspension is generally crap, and the shock loads over potholes can be high. So avoid an outboard which is much heavier than manufacturer's recommended, and make sure there are trailer rollers right under the transom, and try to drive more on smooth roads than potholed!
 
Not too sure on this but I would imagine it could invalidate your insurance or make it difficult to make a claim if the outboard is more powerfull than the manufacturers recomended maximum.
 
When i was doing my ym, we were doing night exercises when we bumped into a couple of sbs boats out of poole, over a mug of tea, they mentioned they had downgraded to twin 250hp ob as the previous larger versions cracked the transom. these guys were rammin round the solent with no lights at all, doing approx 50kn /forums/images/graemlins/smile.gif
 
Mmmm, thanks, I hadn't even thought about the towing element and the trailer, I suppose as you said, if the transom is well supported by the rollers then there should't be a problem. Great stuff.
 
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