TOPIC: shaft length

Hi all,

I have been in search mode for a larger engine to re-power my boat. I have come across quite a few 55 and 60hp loopers on craigslist, but just from looking at the pictures I cannot tell exactly if they are a short shaft or longshaft.

On the old big twins it is easy to tell because of the obvious 5" spacer in the lower unit. Is there a way to tell with the late 60's early 70's loopers as well?

If I do happen to find a good longshaft for cheap is it possible to convert it to a short shaft? What all does that entail? Is it as simple as removing a spacer and getting a shorter shaft / cutting down water tubes, or are these more complicated.

Sorry for the long post... I appreciate any info you can give.

Scott

Hi, Scott, I've attached a pic of a 55hp Shortie Johnson Twin for reference. You'll note the short distance from the "horse collar" lower wraparound cowl, to the lower unit. A Shortie Three will be very similar in appearance.

On the older JohnRude motors with a 5-inch extension, how easily they convert back to short shaft depends on how the conversion was done in the first place.

If the long shaft kit was installed after the motor came from the factory, there typically will be extensions on the water tube(s) and shift rod. Those can be easily removed or changed to short shaft configuration.

Whereas if it came from the factory as a long shaft with extension already installed, more likely it'll have longer water tubes and a longer shift rod coming out of the lower unit.

In the latter case, you could cut 5" off the water tubes but you'd still have to deal with the too-long shift rod. 2 ways to do that, cut 5" off the rod and grind a groove in the end, or dismantle the lower unit and install a short shift rod.

And in any case the longer driveshaft would have to be changed-out to a short.

Hope that clears it up a bit. Of course, it'd be a lot simpler to find a short shaft motor, but they're getting quite rare nowadays!

Cheers..........ed

Scott - the Short shaft motors are more difficult to find because fewer were sold. Unlike the earlier OMC engines These later models have significant differences between short and long shaft configurations.

The exhaust towers are once piece - no extensions.
The motor tilt casting and swivel pin are different lengths.
The drive shaft must be changed - and it is NOT an easy swap.

Short shaft parts are around, but they are usually pretty costly. If you have no choice, then you can do the conversion, but it's a fair amount of work. Probably best to try for a shortie from the get go.

I clicked a photo in the boneyard for you today. Notice the long shaft in the background and the shorty in the foreground. Look at the distance from the exhaust relief ports to the lower unit flange. Also, note that the lower motor mount on the shortie is WAY up on the exhaust tower as compared to the 20" model.

Good luck with the search - hopefully before Summer you will have found one.

Hi Guys,

Thanks for all the info. The pictures really help me to visualize short vs long.

Still no real luck finding one, but I did run across this craigslist ad: grandrapids.craigslist.org/boa/4875213900.html

If you look at the last picture, it shows what looks like a 5" spacer. I'm guessing that this engine was originally a short shaft and someone converted it to long? It seems that this would be easier to convert back to a short shaft.

I am half tempted to pick this engine up as a spare, but haven't fully decided yet. I contacted the seller and he is going to run compression for me.

motoscott909 wrote:

If you look at the last picture, it shows what looks like a 5" spacer. I'm guessing that this engine was originally a short shaft and someone converted it to long? It seems that this would be easier to convert back to a short shaft.

I've got a spare extension .....but it is for a Merc

Sure enough! It is indeed a shorty with a leg extension. The drive shaft is the big unknown, but it also appears to be a short one. The lower unit is hydro electric, so no shift shaft to deal with. I'd say it's worth looking at - at least for parts. It is likely a 1968 or 1969 - but I believe a later 70-75 powerhead will bolt on.

I was trying to find the same thing, a short shaft looper. Thought I found one and drove 150 miles to look at it. Got there and it was a 20 inch shaft. The young man that was selling it called it a short shaft because he thought the extra long shafts were long shafts and the regular length (20") were considered short shafts. He is probably right because I found out later that 20" shafts are usually referred to as "short". Well I ended up buying the motor because it was a low houred 1979 55 hp Evinrude. He said it was his grandpa's and it set in the garage most of its life and was never stored with gas in the carb. He'd crank it every now and then. So I snatched it up for $600 because it was worth every bit of it. I built a bracket and built my transom up 4 inches because my 61' Crestliner runabout was designed for a 15" shaft. Just an idea, but a bracket might be something for you to think about if you can't come up with a short shaft.