securing my 25 horse mercury engine to an aluminum boat

C

checkeredflags

Recruit
Joined
Aug 6, 2007
Messages
4
I have an old (1774) 16" aluminum boat and although the wooden transon seem secure there is a risk of it breaking as the engine (25 horse engine mercury 180 pounds) is placing a great deal of strain on it. I want to to drill two additional holes through the thin aluminum below the wood transom 1/2 " in diameter in order that I can install two extra bolts in the engines mounting bracket. There are two bolts going through the transom above the water line that go through the wood; however I need additional reinforcement and this will require that I drill two holes through the thin aluminum below the wood transom to bolt the lower portion of the engine mounting bracket. I thought I would use a thin steel plate on the inside of the haul and drill two holes (1/2 " dia) through the thin aluminum haul below the wooden transom. I'll then run 1/2" bolts through the aluminum and the reiforcement plates and bolt it down. My concern is leakage since this will be right at or below the water line...not sure what to do. Is this practical and if so what type of sealant should I use to prevent leakage......Pleasae help as I do not want to loose my engine
 
diaric

diaric

Chief Petty Officer
Joined
Jul 8, 2006
Messages
532
Re: securing my 25 horse mercury engine to an aluminum boat

probably should be in boat topics, but post a pic of your set up, and it would be easier to answer
 
ddennis

ddennis

Petty Officer 1st Class
Joined
Aug 15, 2006
Messages
351
Re: securing my 25 horse mercury engine to an aluminum boat

Pics would help, but if not use 3m 4200 or 5200 sealant. Why do you think you need to reinforce it? is the transom flexing?
 
S

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: securing my 25 horse mercury engine to an aluminum boat

checkeredflags said:
I have an old (1774) 16" aluminum boat and although the wooden transon seem secure there is a risk of it breaking as the engine (25 horse engine mercury 180 pounds) is placing a great deal of strain on it. I want to to drill two additional holes through the thin aluminum below the wood transom 1/2 " in diameter in order that I can install two extra bolts in the engines mounting bracket. There are two bolts going through the transom above the water line that go through the wood; however I need additional reinforcement and this will require that I drill two holes through the thin aluminum below the wood transom to bolt the lower portion of the engine mounting bracket. I thought I would use a thin steel plate on the inside of the haul and drill two holes (1/2 " dia) through the thin aluminum haul below the wooden transom. I'll then run 1/2" bolts through the aluminum and the reiforcement plates and bolt it down. My concern is leakage since this will be right at or below the water line...not sure what to do. Is this practical and if so what type of sealant should I use to prevent leakage......Pleasae help as I do not want to loose my engine
Click to expand...

1774 Thats over 200 years old.Must be a dug out aluminum. ! would think your 25 is closer to 100 lbs unless it's a 4 stroke and that would put it at 160 lbs.
I would think your boat is rated at least at 25 hp and perhaps more.
I don't see that a plate on the inside with just the 2 bolts would add much strength except for support right at the bolts And you could do that with a couple of beefy washers.I think I would add plywood the same as the transom
and bolt it to the aluminum.I'd use pt ply with a couple a coats of sealer.
it will last a lifetime.
 
Chinewalker

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: securing my 25 horse mercury engine to an aluminum boat

Why do you think your transom is insecure? Is it cracked? Is the wood core rotted? If the boat is rated for a minimum of 25hp then you should have no problem clamping the motor on as it was designed, with a pair of bolts through the normal holes for security...
- Scott
 
You must log in or register to reply here.
Top