Old motor conversions/power

[restornator]

I've read about the fuel pump conversion from a pressurized tank to single line, but what other conversions have been tried on these old motors?

has anyone tried replacing the cylinder head with a later model head w/ thermostat?

what about the horsepower difference from the FD-10 to FD-12 (15 to 18)? is it simply the carburetor? I also have a 12hp Gale Bucanneer similar to the FD-10, what shortcuts did Gale make to lose 3hp? and would it be reasonable to think that this motor could gain 6hp?

 

[jbjennings]

Re: Old motor conversions/power

Trying to get more power out of these motors is something that requires access to a lot of parts. Something that most folks don't have. I know that a very FEW select men that are OMC experts CAN squeeze a few more horsepower out of the 25's and such, but I haven't heard about anyone doing it on any motors below that. You can't squeeze three more out of the 15's from '53 through '58 as far as I know. I have noticed that the '53 and '54 15's seem to be faster than the '55 and '56 15's, but I don't know why. The 15's are different in more than the carb. for sure. I doubt you could change the heads out because the bolt holes won't match up, I don't believe, and it may change the compression as well---not sure. I personally don't really notice any difference in how my thermostat and non-thermostat motors run.
If you want to ask the guys that would no about this stuff (not me, really), you should hope F-R checks in or post your question on aomci.org on the ask-a-member section there. If it's worth knowing about an OMC motor, GarryfromTampa and F-R can tell you all about it.
JBJ

 

[F_R]

Re: Old motor conversions/power

12hp Gale is 2 1/4" bore, 17.89 cubic inches
15hp is 2 3/8" bore, 19.94 cubic inches
18hp is 2 1/2" bore 22 cubic inches

Before you ask, the 22 cubic inch 20hp and 25hp motors use different combinations of pistons, crankshafts, cylinder heads, and carburetors. So it is not a simple deal to make a 25 out of an 18.

Nor can you bore a 12 out to 15 or 18hp size because you run out of cylinder liner. Same with 15 to 18.

While on the subject, the Gale has aluminum connecting rods and bronze mains. The 15 has roller bearings except for the bronze wrist pin bearings and lower main. The 18 has all rollers.

So, as you can see, outside appearance has little to do with what's inside.

 

[restornator]

Re: Old motor conversions/power

thanks for the info. the real big question i forgot is how do you install a kill switch onto these motors? I have a 63 evinrude fastwin with the kill switch but i dont want to pull the flywheel off to see where the leads are grounded

 

[rjezuit]

Re: Old motor conversions/power

Short the 2 points together with a switch, that grounds them and they will not fire. When the switch is open, they fire when closed they are grounded.
Look here: http://www.duckworksmagazine.com/05/columns/max/3/free.cfm
Rick