Differences between ’50’s era 30, 35 and 40 hp big twins?

[instigator]

quote Pappy:

quote Chris_P:

You CAN bolt a 40hp powerhead, onto a 35hp Super Quiet from ’58/’59 and have a sleeper. As stated, you cannot bolt a 40hp powerhead onto a 25/30/35hp single wall exhaust motor though.

Wanna’ bet?
I bolted up a ’74 40hp single wall exhaust to a 1957 35hp. single wall exhaust engine. Have to cut an eyebrow at the forward end of the lower bearing housing on the crank and match it on the mid section and use the later model gearcase……… Been there done that!
Getting the clamshells to fit was the fun part (Ignition is different) plus a couple other smaller issues. If you cut the late model ventilation plate to match the 1957 profile and paint it nobody is the wiser!

GREAT post!

Typically I listen to all the experts then try it anyway 😆

I mounted a Mercury gear case (for alternate gear ratios) to a couple of hot rod OMC’s so most issues can be tackled.

[chris-p]

Ok, the average guy couldn’t do it! 🙂

I had not considered a single wall exhaust 40hp, that is interesting and good to know thanks! I was only thinking of the superquiet 40hps going onto a single wall 35.

Interesting stuff Pappy Ill play with one of those combos one day.

[adam1961]

The Gale 40s used the single wall mid section right through the years. I like to snap those up when I see them at less than 1$ per pound

[reivertom]

Us "jake leg mechanics" will just stick with buying complete motors that just need a little TLC, and act like we’ve really done something. You Resto-mod guys and hotrodders amaze me ….you all never say "it can’t be done"….even if sometimes it shouldn’t be done! A Merc lower unit on an OMC???? Blasphemy!! :^)

[1946zephyr]

I actually did that, Chris. On the last RDS-21B I owned, I had a 1968 Lark X powerhead on it and it ran nicely. The Lark had a bad lower, so I used the powerhead on a motor that I was using.

Hey Pappy, how about using a 40hp Gale powerhead, on a ’57 clamshell style Big Twin? Would that adapt any easier than the 1971, on Johny/Rude 40?

[wbeaton]

You don’t need counter rotation for motors this small. I helped a friend setup twin 18 hp and 25 hp OMC’s on his 14′ Feather Craft Hawk. Both sets of motors performed beautifully back there. I’m putting a pair of 1962 Johnson 40’s on my cabin cruiser. Twins are every mans dream 😉

Wayne
Upper Canada Chapter

uccaomci.com

[1946zephyr]

Nice sets of twins 😉

[instigator]

Very cool! Love it.

[instigator]

Here’s my project hull.
Notice how wide the motor board is. Most of this model were narrower for a single motor.

BTW, found another 35 on craigs but of course it’s 2 hrs away, as they all are.

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[instigator]

The final pc’s of the puzzle.

Pick these up next weekend.
‘1957 35’s.

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