Johnson 15hp convert long to short shaft.

[Rays14ft.]

Have a real nice 1994 Johnny 15hp (J15RLERE) long shaft. I would like to convert it to a short shaft to use on my 13ft Valco. Can anyone detail the swap as far as what all is needed, and possible parts sources. Im ok with used parts. Also what years will interchange. Thanks.

 

[ondarvr]

Raise the transom, much easier and will cost less. But...many people want long shafts, so you may be able to trade with someone.

 

[Rays14ft.]

I was looking at the jack plate idea. Seems they all offset the motor back 4 inches. That could be a problem as I only have tiller controls.

 

[ondarvr]

Much easier than a jack plate. Two thin pieces of aluminum that sandwich plywood that matches the current thickness of the transom, the plywood sets right on top the transom and the alumuinum covers the new plywood and down 12" or so down onto the existing transom. This is very strong and you can get the aluminum at a scrap metal place, or have it cut. A few bolts and you're done.

 

[oldboat1]

Thought I might take a look at that hull, and happened to run into one that has been altered like Ondarvr suggests. Looks good, and have to believe handling might be enhanced too: http://forums.iboats.com/forum/gene...questions-not-engine-topics/312140-valco-deal

Think I like it -- was going to talk about a motor conversion, which would still be a possibility, but think doing the transom might be a first choice.

HOWEVER, as an alternative you might look around for a suitable '90s parts motor. You need the shorter driveshaft, which would come with a substitute lower unit. Your water tube would need to be shortened (tubes are attached to the powerheads), and that is an easy matter. A shorter shift rod would also be part of the l.u. assembly on the substitute unit. (You want both a driveshaft and shift rod, because you can get hosed pretty good buying those parts separately.) I would think a lower unit could be had for two or three hundred, maybe less. Complete parts motors? Look around. I bought a '91 electric a year or so ago for $200, and that was probably on the high side -- think I would look for complete motors first, but keep an eye out for lower units. You need an old time marina with a decent boneyard and cooperative owner. Good project, however you go about it.

 

[Rays14ft.]

That's seems like a good idea vs. Changing out the lower unit. I looked at the Valco in the above link and it looks done nice. So if I redo my transom boards all together but 5 inch taller and cover in gauge aluminum? to do that I would need to cut open the channel aluminum that captures the current boards. Or do I stack the new boards on top of the current transom boards? Any guesses on thickness needed? Any mods to inner support leg? Sorry mods, this topic moved away from engine repair.

 

[scout-j-m]

So are the 93 and up models harder to convert than the 70's-92 models? When I did my 1982 long to short shaft all it required was a short shaft driveshaft, short shift rod, and cutting the water tube with a dremel. I had a parts motor so there wasn't any cost but I did look on Ebay and the driveshaft and shift rod could both be had for much less than $150 total if I remember right. You could also sell your removed longshaft parts back and possibly break even. This is all contingent on the conversion process being similar for your year model.

Making the transom extension is a perfectly fine alternative and is probably cheap but then you also have to drill holes in the transom which I would want to avoid personally.

 

[hardwater fisherman]

^^^ Some good points there. Also if you raise up the transom than you will be stuck with that motor. Where I live long shaft motors in that hp range are rare. My nephew built up his transom for a long shaft 15hp Merc. And he likes to fish on lakes that have a 10hp limit and now he has 2 other small motors that are too short. Just some thoughts.

 

[ondarvr]

It easy to convert it to a short shaft, you just need to find the parts.

You aren't stuck with a taller transom after raising it, reversing it is done by simply unbolting the riser and removing it, now you're back to the the short shaft length.

Drilling holes is a non issue, not even something to be concerned about.

You just stack the new plywood directly on top of the old transom, the only thing that overlaps down onto the old transom is the aluminum plate on both the inside and out side of the transom. This assumes that your current ransom is in good shape, if it's in bad shape you will need to fix what's wrong with it first.

 

[hardwater fisherman]

Ok stuck was a poor choice of a word . I know it can be reversed by just unbolting it. Also for the example I gave it would be a lot of work for a day of fishing. And if unbolted you would need to fill the holes and let that dry before using.

 

[oldboat1]

Another option would be a stationary mounting bracket (effectively, a transom bracket). Find a used one, or make one. Set the height for what you need for the current motor. Removal would be a matter of maybe four bolts.

Or....find a couple of transom clamps from a donor motor and add a mounting board for the height needed (another transom bracket, but without any transom through-bolting). Clamp the assembly to the transom and mount the motor. I've done this for an offset trolling motor mount on a Boston Whaler with a curved transom, and it works well. Make the mounting plate as fancy as you want to dress it up a little. Advantage is complete portability, and cheap to put together.

 

[Rays14ft.]

Ok guys thanks for all the advice. I believe I will go the raised transom mount

 

[thumbnut]

If you make it wide it might help keep water from spilling over the transom...wished I did that with mine...