Outboard bracket material

[Yachtingsouthwest]

Hi

Need to extended the height of my outboard pad that is premoulded into the hull on my trailer sailer. What would be a good material to bolt onto the existing bracket.

The dimensions of the material needed is 300mm x 300mm around 25-40mm thick.

 

[VicS]

Hi

Need to extended the height of my outboard pad that is premoulded into the hull on my trailer sailer. What would be a good material to bolt onto the existing bracket.

The dimensions of the material needed is 300mm x 300mm around 25-40mm thick.

The mounting board n my outboard bracket is made of two thicknesses of marine ply glued together..............from an old piece that had been on the boatyard wood pile for several years without any signs of delamination.
If I had to make another it would be from an old teak laboratory bench top because that is what I have available

 

[rogerthebodger]

I would use Ultra High Density Poly Ethene

I used multi thickness Ply but it rotted over time

 

[Tranona]

Hi

Need to extended the height of my outboard pad that is premoulded into the hull on my trailer sailer. What would be a good material to bolt onto the existing bracket.

The dimensions of the material needed is 300mm x 300mm around 25-40mm thick.

Why do you want to raise it? Boats with built in mounting boards are designed to take either standard or long shaft motors so you choose the correct size motor to suit.

As to thickness 25-30mm is OK up to about 6hp and 35-40mm for up to 10hp or maybe 15. usually as Vic says laminated layers of ply but could be good straight grained hardwood.

 

[Hadenough]

I would use Ultra High Density Poly Ethene

I used multi thickness Ply but it rotted over time

£££

 

[Yachtingsouthwest]

Why do you want to raise it? Boats with built in mounting boards are designed to take either standard or long shaft motors so you choose the correct size motor to suit.

As to thickness 25-30mm is OK up to about 6hp and 35-40mm for up to 10hp or maybe 15. usually as Vic says laminated layers of ply but could be good straight grained hardwood.

When the boat was built it was designed for a short shaft engine which were specced around 5inches shorter than modern SS outboards. There is a skeg that protects the outboard leg when taking the ground so the skeg on the boat and outbaord need to be inline.

 

[Tranona]

The key dimension is not the outboard in line with the skeg, but from the top of the board to the waterline. Typically that will be 15 or 16" when the boat is static and the waterline should be above the anti cavitation plate. Raising the engine 5" will likely mean that it is insufficiently immersed. I think it unlikely that a builder would mould in a mounting board 5" too low. So before you make any changes measure the distance from the top of the board to the waterline. The skeg may not be designed at a height below the bottom of the leg as the motor should be tilted or raised when the boat takes the ground.

What boat is it?

 

[Yachtingsouthwest]

The key dimension is not the outboard in line with the skeg, but from the top of the board to the waterline. Typically that will be 15 or 16" when the boat is static and the waterline should be above the anti cavitation plate. Raising the engine 5" will likely mean that it is insufficiently immersed. I think it unlikely that a builder would mould in a mounting board 5" too low. So before you make any changes measure the distance from the top of the board to the waterline. The skeg may not be designed at a height below the bottom of the leg as the motor should be tilted or raised when the boat takes the ground.

What boat is it?

Its a Swift 18 the boat was built in the 80s and from researching it was designed that the outboard was protected by the boats built in skeg without tilting the engine. The outboards originally specs for the boat had a shorter leg than any modern outboards available

 

[Tranona]

Its a Swift 18 the boat was built in the 80s and from researching it was designed that the outboard was protected by the boats built in skeg without tilting the engine. The outboards originally specs for the boat had a shorter leg than any modern outboards available

Shaft sizes have not changed for petrol engines (but are slightly different for electric). They have been 15/16, 20/21 and 23/25 inches for over 50 years. Your pad is almost certainly set at 15" from the waterline - even if that leaves the bottom of the gearbox skeg below the level of the skeg on the boat.

For completeness there was an exception. Seagull made a 13" shaft length specifically for use on Avon dinghies which were designed for that size. There were no other shorter legs in the 1980s. All short shaft were 15 or 16 inches, same as today.

 

[thinwater]

I would use Ultra High Density Poly Ethene

I used multi thickness Ply but it rotted over time

That is ultra high density polyethylene (UHDPE).

(Chemicals are never capitalized. Spelling usually counts, but in this case it is less critical, because ethene and ethylene are the same thing ... but the plastic is not spelled that way.)

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I do not like HDPE for mounting outboards because it is so damn slippery. If the screws loosen or the plastic creeps over time, the engine can jump off. Better to replace exterior ply once in a while.

motor comes off (not HDPE, but funny)
another one
and another