Long shaft on a short shaft boat?

[TopQ1967]

Hi,

Is it possible to run a long shaft engine on a boat designed for a short shaft engine?

What are the disadvantages if it is possible?

Reason to run a longshaft on a short shaft boat: I need a longshaft engine (6HP) for my sailing boat and like it to use a smal RIB or SIB as well.

Cheers

Q.

[Mattywooo]

Hi there mate,

I used my johnson 7.5hp longshaft on my 3.3m SIB which is designed for shortshaft.

Dis,
To get to speed you will need to weight the front of to boat down as it will push the front up more rather than forward. For this i use my mate. Top speed will be a little slower as more drag but you dont really notice it.

Engine longer so weighs a little more, bit more effort to lug around.

Adv,

None.

I have now just installed a marine ply raiser on my transom to raise it by 5 inch, works well, speed better.

Im new to boating so please excuse me if i have confused you a little,

Hope this helps.

Cheers 8)

[m chappelow]

i too run a long shaft on my boat ,as i use the same engine on my hard displacement fishing boat,,
you say your boat is a sailing boat.. a normal longshaft should be ok but i would draw the line with an ultra long or extra long saildrive engine .
down sides and depending on the type of engine and tohatsu seem the worse as there is a flat on the leg ,, though some boats can get a lot of spray kicking up and back into the boat and a slight drop in speed also the engine is going to be 5 inches lower so it means that the engine will have to be tilted up sooner when running in very shallow water and if you pick up a plaggy bag or diver in the prop you will have another 5 inches or so to lean out and clear the prop ,,advantages are that the engine wont airate or cavitate as much if going over big waves or in tight turns as the prop is always below the water ,

to stop the spay side of things i just cable tie some thick rubber spray deflectors on the leg above the water line and infill the flat on my leg with a shaped block of wood as in the pic below.

[joebhoy18881977]

I have now just installed a marine ply raiser on my transom to raise it by 5 inch, works well, speed better.



Any pics matty