Problem changing from long shaft to short shaft

[jimchardy]

I just purchase a 40 hp 4 cycle merc short shaft motor and previously had a 20 hp evinrude long shaft. The merc has an 11 degree pitch 3 blade stainless prop. My boat is a 16' tracker and the distance from the top to bottom of transom is 20"<br />I have difficulty maitaining power-if I open up the tiller throttle all the way, the I get a high revving sound from the motor but no speed-my guess is that I am experiencing caviation. If I gradually increase the throttle, it will come up to plane but will not alway hold plane-sometimes it kind of wallows. I have a humminbird with a speedometer indicator-shows top speed of 18 mph.<br />Any diagnoses or solution would be appreciated.<br /><br />jimchardy

 

[Coolmaker]

Re: Problem changing from long shaft to short shaft

You can always cut the transom down 5"..... Then the short shaft will work... -)))))))

 

[Laddies]

Re: Problem changing from long shaft to short shaft

Why did you think a short shaft engine would work on a long shaft boat, I don't belive mercury builds a extention kit, years ago there was a company Bay Pattern in Ohio that built kits for mercury outboards

 

[DHPMARINE]

Re: Problem changing from long shaft to short shaft

The guys above have it.You need a long shaft motor.I made this mistake 22 years ago.Haven't gotten over it yet.<br /><br />DHP

 

[NathanY]

Re: Problem changing from long shaft to short shaft

You could try a 5-7 inch setback. Motor does not have to be as low in the water when a setback is used. Or maybe a jackplate?

 

[jimchardy]

Re: Problem changing from long shaft to short shaft

Originally posted by Laddies:<br /> Why did you think a short shaft engine would work on a long shaft boat, I don't belive mercury builds a extention kit, years ago there was a company Bay Pattern in Ohio that built kits for mercury outboards

 

[jimchardy]

Re: Problem changing from long shaft to short shaft

I HAVE CHECKED WITH A LOCAL BOAT DEALER AND THEY THINK THEY CAN GET ME A BAY EXTENSION KIT INTALLED FOR AROUND 500.00 THAT IS A LOT LESS MONEY THAN ANY OTHER OPTION I CAN IMAGINE.<br /><br />THANKS FOR THE INFO

 

[wilde1j]

Re: Problem changing from long shaft to short shaft

Have you checked here (and other places the make jack plates)?<br /><br /> http://www.bobsmachine.com/ <br /><br /> http://www.cabelas.com/products/Ccat420001.jsp <br /><br />Way less money (~ $200) + labor (not much).