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Old 28 March 2004, 12:08   #1
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searider transom mod....help please

Hi

I have been running about in my 4m searider since christmas with a 30 hp mariner. Ive now got a 1999 50hp mercury with pt&t and am a bit worried about putting such a big, 93kg, engine on a small boat which is close on 20 years old.

Although the transom is showing no obvious signs of weakness, apart from the ply panel on the outside starting to delaminate at the edges, I would feel a lot happier if I beefed it up a bit.

I am thinking of sandwitching the transom with 1/4 inch stainless steel plate to help distribute the weight of the engine over the full transom, hopefully reducing localised stress around the mounting points.

I am sure a few of you have done this type of thing before and would appreciate any guidance you could give me.

cheers

Stuart
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Old 28 March 2004, 12:41   #2
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Boat name: The Nashers Revenge!
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Hi

Have a look at my website www.flatacraft.com and see how I did exactly what you are suggesting to my Flatacraft Force 4 when I put a 55HP Suzuki triple on it.

I'm getting it ready to sell by the way!

Nasher.
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Old 29 March 2004, 02:11   #3
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Country: UK - England
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Boat name: Tango
Make: Avon and Narwhal2.4m
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Engine: 60HP Yamaha
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mojo - Firstly you need to make sure the transom is completely sound, the fact yours is 20 years old would make me suspicious that it could be taking in water, mine did and i've just had the entire marine ply core replaced, the plates bolted on will make it stronger but if the transoms weak to start you may just be moving the stress points further along, those triangular elbows older avons have fitted are hollow ! there's very little structural strenght in them at all and it was these points that tore on my transom first indicating a problem.
I believe a 4m can take a 50hp but for peace of mind make sure the transoms sound before you go further, a heavier engine with more torque will damage a weak transom in no time.

Rat
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Old 29 March 2004, 18:44   #4
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bilge rat, you make a very good point and exactly what im worried about. I would have thought that replacing the transom would have to be done in conjunction with a retube, is this correct? if so it is way beyond my scope. If you wouldnt mind, I would be interested in how much it cost you for a new transom, pm if you wish to be discreet.

In my favour I would reckon about 8 out of 10 20 year old 4m seariders seem to be running about with 50s on the back with no problems, but as the 3 cyl merc is absolutely huge for a 50 at 996cc I dont want to take any chances.

Stuart
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Old 30 March 2004, 01:55   #5
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Hi

I certainly checked out the state of the transom on my Flatacraft before bolting the big engine on, and only went ahead when I was happy it would take the strain.

My 55Hp Suzuki was that much heavier I needed to move the trailer axle back about 4 inches to restore the nose weight but didn't appear to affect the balance of the boat too much. The big differance over my old 40Hp was pulling skiers out of the water, and of course top end speed.

Nasher
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Old 30 March 2004, 02:51   #6
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mojofilter my transom repair cost me 200 plus lifting and re fitting the engine, some stainless steel work and a new elephants trunk, the guy that did the transom is a specialist who builds fast fishers for a living and really knows his stuff, because the ply inside the transom was so rotten he was able to chisle it out from the top and epoxy in a new board, cut the holes and refit the drain trunk, he also made an epoxy cap on the top of the ply which will make it impervious to water ingress.... then it went back to my mechanic who had a stainless steel cap made to top the transom and re commissioned the engine.... the boat then went to someone else local who does tube repairs as i had a leek in the rear starboard tubed which was aggravating me .......dont be scared its not that difficult to remove and re glue the tubes back on, if you know what your doing of course, and its the best way to patch a repair from the inside.
In total its cost me about 450 which i could have reduced had i not had the tube repairs done and lifted and re fitted the engine myself, now though the transoms the strongest part of the boat.

I'd suggest before investing any money at all take a good hard look at your transom, remove an engine bolt and see what the ply inside is like, use something sharp and have a dig at it, if its soggy your'll know straight away, also worth lowering the engine, get a good hold of it and see if you can flex it up and down, if the transoms going it will wobble up and down quite easilly and your'll see the transom flex. I was lucky as i caught mine quickly, i knew i had a problem but kept ignoring it until one morning at the slipway a mate of mine spotted these nasty splits in the inside gell coat indicating a problem, that day we went to the pub instead !!
Bottom line is they can be fixed and to someone who knows what they are doing its no big deal !

So bigger engine on 4Metre boat
You should PM Phil davies as we've had this conversation about 4m boats with big engines for ages now, there's a list of things you need to take into consideration when fitting a bigger engine to a small boat, weight to power ration, extra fuel, insurance, trailer, transom, position etc.

Richard
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