Transom reinforcement needed??

MystyBlue2

MystyBlue2

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Hi folks i may have the opportunity to grab a bargain and get rid of my mariner 25 2 stroke and grab a mercury 40hp 2 stroke electric start only,

My issue is my boat is a small 12ft seahog and im sort of worried that the weight and torq of hp increase may stress my transom, has anybody got any advice or tips on best way to reinforce my transom to cope with the added stress without cutting out whole transom and glassing in a whole new thicker one?

My boat is a 12ft version of the 14ft seahog trio

Cheers folks
 
Dan208 said:
Hi folks i may have the opportunity to grab a bargain and get rid of my mariner 25 2 stroke and grab a mercury 40hp 2 stroke electric start only,

My issue is my boat is a small 12ft seahog and im sort of worried that the weight and torq of hp increase may stress my transom, has anybody got any advice or tips on best way to reinforce my transom to cope with the added stress without cutting out whole transom and glassing in a whole new thicker one?

My boat is a 12ft version of the 14ft seahog trio

Cheers folks
Click to expand...
Hi find out what the boat builder suggests and don't exceed the HP/weight they recommend. Jim
 
For other readers reference, here is a Seahog Trio for sale - she also has a 25 hp 2 stroke O/B motor.
However she is 14', not 12'.

Buy Seahog Trio | Seahog Trio for sale

Dan, re how your boat is 12' rather than 14', was 2' simply chopped off the stern?
If so, was this done later on after the boat was built, or was she originally built like this?

Can you maybe post a photo or two of your boat please?
 
The seahog trio is a version of the old CJR, i have never heard of a 12ft version, the hull pounds badly, very stable at anchor though, i would not put 40 horse on a 12ft version, the hulls get stress cracks at the best of times! they plane well with 25 horses.
 
Mmmm ok guys thanks for your replies, i have just recieved a message from seahog boats and they said it was a 12ft open version of the trio, never in full production, that explains why ive never seen one before and cant find another lol,

They also said the boat is suitable for a 30hp...

Im assuming this would be rated for modern 30 4 stroke which are quite heavy

Even though im looking at a 40 im told it only weighs 70kg as a 2 cylinder, this is still lighter than a modern honda 30 4 stroke for instance
even though its bigger,

Could i glass in a couple of triangular gussets between transom and deck on the inside to try and eliminate any horizontal transom flex and also bolt on a 3 or 5mm aluminium sheet on back of transom to stop any damage where its bolted to boat?

I have no intensions on WOT as in my head high speed stability will be massively compromised but will have enough power to get on plane and back off to cruise with a bit of back up power left on throttle if needed.

I had a mariner 25hp 2 stroke and with 2 people and minimal gear i NEVER planed out, it draged its back end and 8KN max. Which i think was way overloading a small engine and i was waiting for it to blow up.
 
Any advice on reinforcing or it it still a no go!

There seem to be a few of TRIOS online with big heavy 40 4 stroke elec start with power trim. Thats a lotta weight for a 14ft IMHO but they seem to hold it,

Any particular reason i cant put on a lighter 40hp 2 cyl elec start manual trim on mine with a bit of beefing up, i dont have to give it the beans and will probs NEVER WOT but its there just incase i need it,

Advice please the guy has the motor ready for collection but dont want to commit if its going to cause a catastrophic accident or ripping transom off.

Cheers folks
 
Nobody is going to say it will be alright. That decision is yours alone. Things to be aware of. Will insurance cover it? Unlikely unless underwritten by a marine surveyor. (BTW its either illegal or soon to be illegal to over power a boat yourself) No insurance = no launch. These older boats are notorious for transom rot so you need to be absolutely sure yours is fine before bothering with any beefing up.
 
Dan208 said:
I had a mariner 25hp 2 stroke and with 2 people and minimal gear i NEVER planed out, it draged its back end and 8KN max. Which i think was way overloading a small engine and i was waiting for it to blow up.
Click to expand...

I'd be checking other things first - seems like a 12ft Seahog with a 25hp 2 stroke should get on the plane without too many problems. Prop sized correct? Dirty hull? Correct length shaft?
 
Yup everything checked as much as i could, hull os clean it stays on my drive and on bunks so hull is spotless, the whole deck has been replaced and soggy foam removed as i thought that was my issue but didnt even see a 1kn improvment, i also had a 10x12" prop on, i changed that out for a 9.9x10 and no differance.

The way i see it my boat is empty, i have a small 50ah marine battery 12kg, anchor weighs 5kg including rope and chain, 30l of fuel 30kg, and 2 100kg blokes and rods and lures and boat will barely move at WOT with a 25 2 stroke,

A while ago i needed to revove boat from trailer to work on fitting a new axle, it took me and 5 of my neighbours to lift a small boat off the trailer and lay it on the ground for the trailer to be worked on, for some reason the boat weighs ton for a 12footer and on other sites there are threads of a similar nature of people with a heavy loaded boat and peoples comments are saying, "if you have a heavy rig you need a bigger engine to push it".

Im totally scratching my head as to why my boat is so heavy, there are no seats in and all the necessary things above and thats it. If i open the bungs not even a drop and the hull is bone dry if i open inspection hatches.

This is why im wondering if a bigger motor without all the heavy additives like power trim and such would get me comfortably on plane and cruise at 17kn.

I maybe wrong and stand corrected as im still a beginner and i will listen and take all your help and advice from the old timers and guys with experience.

My car has 180hp....but i never use that whole 180hp, thats my thinking i may have a 40 but dont mean i have to use all the power to tear my whole boat apart
 
Ok ive had my transom checked by a guy i know that works on behalf of the RYA and runs radio and powerboating courses,

He deemed my transom rock solid and the only wet parts where around the engine mounting holes, the rest is rock solid, he drilled some tiny holes to check the condition of wood shavings and tapped the transom in various places with a mallet all over the back end inside and out. All seems good,

Now he said i could bolt a 40hp straight on and just be carefull and ease throttle and all should be fine as hes seen alot worse over the years with monster motors mounted, he doesn't seem worried at all,

I want to err on the side of caution and fit a transom pad to the outside of transom to help spread the load (make me a bit more confident).

Would it be possible to use a board of 18mm marine or exterior grade ply and fibreglass it with 2 layers, then flowcoat as top finish and use that as a load spreading transom pad bolted at all 4 corners with m10 stainless coach bolts, large washers and nylock nuts and a PU adhesive?

Will 18mm be thick and strong enough?

Any issues using this method and will this be sufficient?

I have the ply and glass left over from a previous job,

Cheers folks
 
Yes my friend did say if i struggle to get insurance he can sort me out with a company he has dealt with in the past, he confirmed that it is by no means in any way shape or form dangerous, he said its like driving, its not speed that kills its the driver. As long as i respect my boat and the power it will have i will be ok
 
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