28 SPL - Long to short convert

[saxis]

Worried about being able to get my Lark VII 40 running on my 14' Fleetform (controls might be shot, Selectric may not be working, needs many other repairs), my brother has an 80's Johnson 28 SPL. He had the powerhead replaced about 3 years ago, ran it for one more season before he had enough and bought a new Suzuki 25 4-stroke. The 28 SPL is just sitting in his shop and he mentioned a while ago that I could use it. The motor wouldn't idle very well despite regular maintenance and tune-ups and he does a lot of trolling. Lately I've been considering my options: Repair Lark 40hp, Brand New 4-stroke, Used hard-to-find 20-40hp remote/electric start/short shaft or Cheap 28 SPL from my brother.

The 28 SPL is almost too good to pass up, aside from the fact that it's a bit rough-running. But, it actually DOES run, recently rebuilt, has all controls and it pretty much boat-ready. Except, it is a long shaft and my boat is 15". I did notice that it looks like it has just a 6" extension though, bolted between the LU and motor. How simple is it to convert these to short shaft? Will I need a new shift cable and drive shaft, or do these just have removable extensions also?

 

[tashasdaddy]

Re: 28 SPL - Long to short convert

easier to do a transom elevator or a jackplate, and leave the motor alone. what year is the 28spl model #??? just could be a carb adjustment, or need a cleaning and kit.

 

[saxis]

Re: 28 SPL - Long to short convert

easier to do a transom elevator or a jackplate, and leave the motor alone. what year is the 28spl model #??? just could be a carb adjustment, or need a cleaning and kit.

The exact year/model # I don't know: Mid-80's. Seems he mentioned at one time that it was an '87. I might be able to use a jack plate, but I have a tiny transom/back end to work with, and it would look extremely odd at the least...

He had it tuned several times by a Johnnyrude dealership, even rebuilt by them and the motor never did idle well in his 5+ years running it. He would never take it back to them because they low-balled the quote to rebuild and ended up charging nearly double.

 

[tashasdaddy]

Re: 28 SPL - Long to short convert

this is a 1966 with a jack plate i built and a 1955 with the same type jackplate.

 

[marquette]

Re: 28 SPL - Long to short convert

i put a 1986 28 SPL on one of my boats last summer. i looked for a short shaft conversion and as far as i can tell there never was a short shaft version. that piece that looks like a 6in extension in the middle of the shaft is normal for that motor. i was told that the 28 spl was primarily marketed to be a cheap motor for pontoon boats. the part that really sucked was that the 28spl is on the long side of tolerence for a long shaft motor and my transom was on the short side for a 20 in transom. i ended up using a mini jacker to get the motor to the right height. but as far as trolling or staying running mine runs as smooth as any 25-35 johnnyrude from the 80's. i have no problem with the way it runs or idles. it is pretty good on gas. gets about 30 mi per 6 gal tank running WOT between corpus christi and baffin bay. prop selection isn't all that limited but a little harder to find than for a 25-35hp thru hub exhaust. if the mechanic he took it to can't get it running right i would look for another mechanic. it's a pretty lightweight motor so one of TD's transom elevators should work just fine with it.

 

[sturdavj]

Re: 28 SPL - Long to short convert

I also own a 1988 28SPL, from what I understand the "L" represents long shaft.

What I am not sure about is if they made a 28 hp that was not an SPL model.

Seems to me I read somewhere this motor is a conglomeration between a 25 & 35 hp; a 25 top end with a 35 lower end.

Someone will jump in here and let us know if I got backwards, or totally wrong......

 

[tashasdaddy]

Re: 28 SPL - Long to short convert

the SPL stands for special. it is a 30 hp motor with out auto oil mixing, and other features. it only comes in the long shaft. BRP site shows 2 motors the US built and the Venezuela built motors.

same for the 48 spl 88spl 112 spl.

 

[saxis]

Re: 28 SPL - Long to short convert

I also own a 1988 28SPL, from what I understand the "L" represents long shaft.

What I am not sure about is if they made a 28 hp that was not an SPL model.

Seems to me I read somewhere this motor is a conglomeration between a 25 & 35 hp; a 25 top end with a 35 lower end.

Someone will jump in here and let us know if I got backwards, or totally wrong......

I've heard similar: The "SPL" was part of the model, "28 Special", as that's how it is listed in the J/E 2-70hp Shop Manual. I just saw a few pages preview, but it did not have the exploded view of the 28 SPL. It's kind of a strange crossover, because there are many references in the manual about "use part C (except 28 Special)". Like this excerpt: "All models (except the 28 Special) use spiral bevel gears for smooth, quiet operation.". It looks really confusing, as you have a section for 2-25hp, then a section for 25-70hp, and the 28 SPL is referenced all over the place...

Cleaning up that old Lark 40 is looking better all the time...

 

[saxis]

Re: 28 SPL - Long to short convert

the SPL stands for special. it is a 30 hp motor with out auto oil mixing, and other features. it only comes in the long shaft. BRP site shows 2 motors the US built and the Venezuela built motors.

same for the 48 spl 88spl 112 spl.

Looks like it...

28 Special Models: This engine is factory-equipped with a 5 in. extension housing.

 

[sturdavj]

Re: 28 SPL - Long to short convert

28 SPL= Special; makes more sense.

I am embarrassed to admit it but for some reason I had it in my head that SP stood for Special and the L stood for Long shaft.

No doubt about it, the manual for my motor is a different kind of bird.

 

[CATransplant]

Re: 28 SPL - Long to short convert

Well, if the extension is bolted in, it's probably possible to convert it. The problem is the drive shaft. If there isn't a short one that will work in that powerhead/lower unit combination, then you're hosed...unless you can come up with a way to shorten yours by exactly the length of the extension. A really good machine shop could probably do it, using a sleeve coupling on the joint, about midway up the shaft. Any error in the length should be on the short side. If it were me, I'd make it 1/16" short, just to make certain. The splined top end has enough room to compensate for that. Too long, though, and it won't work at all. There's no reason it wouldn't work, but the coupling would have to be capable of handling the 30 hp or so. Perhaps a welded coupling.

Then again...there might just be a short-pattern driveshaft that would work. What I'd do is start looking at the 25 and 35 hp models around those years. Look for a matching part number for the long driveshaft. If you can find that, the short driveshaft for the same model should work. The extensions are all 5" long, as far as I know.

A nice puzzle to solve.

 

[marquette]

Re: 28 SPL - Long to short convert

the 28SPL is a combination of new and old. the powerhead is the same as the 35hp that was redesigned i believe in 1976 that was then used for the 25 &30hp also when they were redesigned in the early 80's. all three motors went to a lower unit with thru hub exhaust when they were redesigned. the 28SPL has the lower unit without the thru hub exhaust that was used on the 25hp Commercial. which i have been told is the same lower unit that was on the 25-35hp before they were redesigned. my factory manual covers all five motors the same except for the lower leg(on the 28SPL & Commercial) and tune up specifcations based on hp. some say the old style lower unit was better because it was simpler to maintain and didn't weed up as easily and others say it is not as efficient as the thru hub design. i bought mine because it was cheap. it's a 1986 i bought in 2008 and the paint wasn't even worn off the skeg. i paid $400 and haven't regretted it at all. it starts, it idles, and pushes a 15ft fiberglass narrow tri hull just fine.

 

[Tolly family]

Re: 28 SPL - Long to short convert

I just finished converting a 1988 28 SPL to a short shaft and can tell you exactly what you need to do. Remove the 5? extension, get a shaft from a older 25 or 30 hp short shaft engine that doesn?t have thru hub exhaust ( I think anything from the about 1971 on will work), get the shift rod and the shorter water tube that goes over the drive shaft also. Cut a 5? section out of the water tube and rejoin the 2 pieces with a union. Put it together. If you can?t find a shift rod just cut 5? off the old one and use a Dremmel to make a small notch for the bolt. The older 25 and 28s are actually 17? from the mount to the cavitation plate so I mounted mine up 2? and bolted it on my 11? Whaler. How I found out what shaft would fit was by cross referencing the original 28 shaft and finding out it was also used in lots of older 25 and 30 hp engines so I just found a short shaft 25 hp 1981 donor for $50.

Dan

 

[CATransplant]

Re: 28 SPL - Long to short convert

Great info. I looked around a little, but didn't go back that far with the driveshaft. That solves the problem.