Proper length outboard shaft

[Jonathan Burnett]

I have a 12' aluminum boat and want to power it with an 8HP longshaft Evinrude outboard.<br /><br />The transom measurement on the boat is 16" from top to bottom of the hull. <br /><br />The outboard shaft length is 27" from top of mounting bracket to the Propeller Shaft. So the propeller shaft is 11" from the bottom of the boat.<br /><br />The beam of the boat is 50" at the Transom.<br /><br />The boat is rated for 10 HP.<br /><br />What do you think? Will this be a safe arrangement?

 

[snapperbait]

Re: Proper length outboard shaft

It'll push it, how well?<br /><br />Best bet is to run an engine with a (short) 15" shaft with your 16" transom...<br /><br />For best performance, the plate on the engines lower unit just above the propeller, the anti-ventilation plate (aka, cavitation plate), should be close to being even with the bottom of the boat...

 

[Jonathan Burnett]

Re: Proper length outboard shaft

Thank you for the advice.<br /><br />If I use this longer shaft outboard, will there be any adverse or unsafe handling characteristics? This is the only outboard I have at the moment.

 

[snapperbait]

Re: Proper length outboard shaft

Adverse or unsafe handling characteristics? Adverse, performance wise, yes... Unsafe, I'd say no... Go for it..

 

[Jonathan Burnett]

Re: Proper length outboard shaft

Thank you Snapperbait.<br /><br />How will performance be affected?

 

[Jonathan Burnett]

Re: Proper length outboard shaft

Thank you Snapperbait.<br /><br />How will performance be affected?

 

[rickdb1boat]

Re: Proper length outboard shaft

Just lower speeds. Any way you can build up the transom with wood or metal?

 

[Jonathan Burnett]

Re: Proper length outboard shaft

That's a good idea. I'll give it a try.<br /><br />Thanks rickdb1boat

 

[lund17]

Re: Proper length outboard shaft

Two years ago I got a good deal on a slightly used 15 for my 14' tin. Problem was a 20" shaft on a 16" transom. I got a piece of 1/4" alum. plate and and folded it over(need a heavy break)the transom from top to bottom with a plywood spacer above the old transom. Bolted everything together like a big samwich and it worked splendidly. Sorry no pictures but alum. is easy so don't be afraid to try. Good Luck!

 

[Solittle]

Re: Proper length outboard shaft

Dad - I run a 1974 9.9 longshaft Johnson on the back of my 12' alumnium skiff with no problems. The rig will get the wife & I up on plane quite nicely (& we ain't small folk). Granted it "should be" a short shaft and looks kind of awkward but it works and works quite well.<br /><br />Howard

 

[cobra 3.0]

Re: Proper length outboard shaft

...just stay away from the shallows!