TOPIC: Short to Long Shaft Conversion

Is it possible to convert a short shaft motor to a long shaft?? And if so, what exactly is involved?

The motor is a '70 1350...

Yes it is possible.
Find a long shaft mid-housing and lower unit and after you remove your short shaft exhaust tuner tube and replace that tuner tube with the one you got with the long shaft stuff, simply install your 1350 exhaust extension plate with this longer tuner tube and then plunk the 1350 on top. U-R-Dun
Best to find a long shaft mid that has all (10) power head stud holes, but an (8) hole mid with work. Just understand that it is critical that you use the exhaust extension plate that is currently in your 1350 rather than whatever EEP might be in the donor long shaft mid.
The donor long shaft mid can be from some of the 650-4cyl Mercs, some of the 800 & 850-4cyl Mercs, 950ss, 1000ss, 1100ss, 1250ss, 1350 and early 1150. (basically any big 4 cyl or inline-6 Merc that uses the thin EEP type mid-housing). '72 and later won't work as they use a very thick EEP and totally different shape of exhaust outlets through the EEP.
The lower unit is best if taken from a 650-4, 800 or 850-4, or any inline 6 after '67 that has the longer shift shaft and is designed to mate with the tuner tube behind the water pump housing.
There are several gear ratios available in the mentioned lower units. 1.78:1, 2:1, & 2.31:1 that can be chosen to best suit the size and weight of the hull to be used. (light-n-fast: 1.78:1, heavy load: 2.31:1)
Thom

Do you mean that you do not like the big fat dumb looking extension kits that make the motors look goofy Thom??

I have a 1350 mid with pwr tilt brackets and rams

Thom, really appreciate the info and i might be picking your brain on this further here soon.

Sent you an email Jim...

Dr. Frankenmerc has been seriously traumatized in the past by extension kits and I can't blame him! They are a real pain to install and the ones I've seen haven't been very well engineered. I've seen some extension 'stub' shafts with severe wear on the splines, this would indicate inferior metal or poor heat treatment.

Much better to find a longshaft tower & lower unit as the Dr. suggested and build 'er the way E.C.K. intended!

I had a '71 1350 LS/PTT on a 16' Sidewinder and it sure did scream! That was a great motor. Besides the PT&T I installed on it, one real nice improvement was using the later-style swept-back-fin lower unit. These are found on '79 and newer Inlines and if you're using the motor on a high-performance hull, will be a great aid in preventing blowout at faster speeds. Besides they look cool!

I picked up the bottom end of a Mariner 115 last year, it's got the later-style L/U and I'm gonna build a '72 1400 powerhead for it. That should run at least as good as the 1300, it'll have the advantage of improved exhaust passages in the powerhead & tuner plate.

Check on eBay, every once in a while you'll see a decent deal on towers and lower units, too.

Your local Craigslist is also a great resource for parts. The one in our area is brimming deals on motors and boats, too bad I and the Dr. are both full up!

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

I just recently went the other way from Long to short..
I had picked up a 1977 115 that had the conversion add-on
so I pulled all the extension stuff out,
Had 5" spacer for the tower, the drive shaft, the water tube,
the shift rod, and the exhaust housing. Pulled all the longer
studs out also. Then everything went back together as a short
shaft late model just great. I have all the left over
conversion kit pieces to sell if someone is interested.
Danny Leger

Did you get another boat Danny? Inquiring minds want to know!

Frank

Frank:
No, no new boat.. Just finding some motors to help out
some of the PC group..

PC1000 wrote:

Did you get another boat Danny? Inquiring minds want to know!

Frank

Darn it. I was hoping you got another Power Cat Danny!

I didn't have much time last night because of a meeting I had, but was able to remove the control box and get it in my shop. New cables should be here today and I want to be ready to install them. Since getting the boat rigged up I haven't had a chance to start the motor, plus I don't believe I hooked up the throttle cable correctly, so either tonight or tomorrow night I'll try and get the new cables in and start that old merc. Leaving after work Friday and out of town for the weekend, so no playing with my boat this weekend!

Thanks for all you do Danny.

Frank

Danny,
Here's a 15C waiting for new love!
Maybe you can share this with the PC guys.

portland.craigslist.org/nco/boa/1736122837.html

I have attached an E-D-B-D picture, but there are better pixs in the CL ad.
Thom

Thanks, Dr.
I had been tracking that one for awhile on Craigslist..
Problem is we do not have many in our owners group in the
Oregon area. There are several folks that would love to
buy this boat, but its too costly to transport.
Danny Leger

Dr_Frankenmerc wrote:

Danny,
Here's a 15C waiting for new love!
Maybe you can share this with the PC guys.

portland.craigslist.org/nco/boa/1736122837.html

I have attached an E-D-B-D picture, but there are better pixs in the CL ad.
Thom

Found a complete 1970 longshaft 115HP for 100 bucks locally...its obviously sat outside for a while as all the red is gone off the cowling but its all there and in very straight shape. If its got good compression and spark, ill make a runner out of it...if not, its got a good longshaft mid and lower that should work fine with my 1350.

Thanks guys for all the help! Jim, i still might be bugging you for a lower and Thom, i might have a few questions about doing the actual conversion once i get tearing into it...