Performance upgrades on 1982 Johnson 115. Any Ideas out there?

[maryhannaj]

Hello everyone. I recently purchased an old Glastron HPV165 Bass boat powered by a 82 Johnson 115(J115TLCNB). It has 108 to 115 compression on all 4, hyd. tilt/trim, good working fuel, electrical and cooling systems, Is propped with a steel 12 3/4 dia. 21 pitch prop, runs between 39 and 43 mph by GPS at 5500 rpm with a full tank, full livewell, myself and all of my fishing and safety gear at 7540 feet of elevation. Cavitation plate sits at abot 3/4 inch above the lowest point of the transom but is lacking a jackplate. The boat is rated at a max hp of 120. I am new to outboards but very handy with mechanical, electrical and hydraulic systems and the tools to work and troubleshoot them. Trouble is, i just dont know the tricks that come with good old experience. I am hoping that the good people here may be willing to help me out with that.
I want more power out of this motor. Any advice on performance upgrades, tweaking and tuning of any kind( that wont end up smoking the motor) would be greatly appreciated! Thanks so much for taking the time to read my post. I am hoping to hear from you!

 

[Bosunsmate]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

You could run a decarb like seafoam through there to see if you can increase the compression ratings, that will smoke it but in a good way

I dont know much about props, there is a prop section on here but a 21 pitch prop sounds very weighted towards top speeed, a lower pitch will give less top speed but more power.

 

[Bosunsmate]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

I see that its not sitting on the transom so you could drop it about an inch and a half or so to get it below the bottom of the transom.
Also thats quite a high elevation. I dont know about jet changes with elevation as I live at sea level but you could check that the carbs have the right sized jetting for that elevation. (especially if you had bought it elsewhere)

 

[Bob_VT]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

I would not touch the set-up of that motor. It is right at the proper height and your rpm's are perfect.

De-carbon the engine is a very good idea too. The 1982 is a crossflow head rated motor for horsepower and there are really no "performance" tricks for that year. The amount of money it would cost and the risk of making the motor less reliable are not worth it.

The glastron's are heavy weights when it comes to bass boat hulls. I would not be surprised if you had some wet foam which adds weight.

Best performance boost for the money is to look for a 1985 or newer V-4 120 HP evinrude/johnson ( a looper is the best and stay AWAY from FICHT motors) or a mercury, yamaha or suzuki which are all prop rated motors. Currently you motor is only (when running it's best and new)about 100 HP at the prop.

One other suggestion....... try a top speed run w/o that fin and possibly try a more aggressive stainless steel prop.

 

[emdsapmgr]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

If you were to install a set of 1 5/16" throat carbs, a set of 140 high compression heads and the 140 rubber intake filler blocks, you'd likely pickup some hp. Probably enough to increase the rpm's 300, which would require that you move to the next higher pitch prop. Perhaps pickup maybe 3 mph. Working on your setup (prop and engine height) are a great way to incr performance with little expense.

 

[maryhannaj]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

I did buy it here. But who knows where it came from before that. Although, the plugs are a pretty good shade of tan, at least at idle speed, with no backfires or hick-ups throughout full range of throttle. Like i had mentioned that i am new to outboards, that is usually a good sign for being within jetting range for bikes etc.. If it should be different, that would be great to know before I really do smoke it. And speaking of smoking it and the seafoam thing, I blew some powertune through it just last week in the driveway and it looked like a dang forest fire in my front yard. Im surprised the fire department didnt show up. Should that have made any type of immediate difference? Thanks for checking out the mount setup on the transom. I have thought that it looked a bit out of wack but also read that the cav plate should be right within that range. In your opinion, would It truly benefit by dropping the cav plate a full inch at least below the bottom of the transom? I also considered putting a jack plate on but didnt spend the bread on it it because of where the motor was sitting and its potential for adjustment range. Is there a true benefit to having a hydraulic jack plate for through throttle range adjustment or would a wrench adjustable jack plate serve the same purpose other than just being a cool option on the boat? I definatly only run it at higher speeds with just myself onboard so as not to put other people in danger but i have always liked trying to get the most out of whatever is within my spending range. Anyway, we just got our first dusting of snow on the mountain tops yesterday and the lakes will all be under ice very soon so i am gonna take it out and run the gas out of it tonight or tomorrow if possible and then start tearing the whole thing apart in the garage for an over the winter restore, something to do project. I will definatly be needing a ton of advice on that, and the knowledge of the best and propper re-mounting of the motor and any other performance effecting information that anyone may have to offer. Thanks for taking the time to respond to my post and any other information you are willing to help with would also be greatly apreciated. Thanks Bosunsmate!!

 

[kbait]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

From the perfect performance you've described, I'd winterize the motor and find another winter project! Unless you just really need to go 50mph..

 

[V153]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

I wouldn't monkey with motor height, Glastrons like it high. I've run em 2" above so at 3/4" you're not too high. Prop sounds about right. I would expect speeds closer to 50 with a light load. Though as mentioned the elevation could have something to do with it.

Those comp #s ain't the greatest, specially the 108. So do a de-carb as suggested. If that doesn't raise the compression much it might be time for a rebuild/rebore.

Having said that. The factory bolt on performance mods are bigger 1 5/16" carbs & reed stuffers, bubble butt exhaust tuner w/filler blocks, and hi-comp heads. Non factory bolt ons include jack plate/backset, performance prop(s), nose cone with low water pickup, trim tabs, etc. If ya got deep pockets'n wanna get into custom machine work then the sky's the limit.

Regardless, those models weren't particularly light to begin with. ~1000lbs dry is heavy for a 16' Glastron. Toss in a 300+lb motor w/controls & battery(s), 18 gal of fuel, full live well(s), passengers & gear, and it adds up purty fast. Weight is the enemy. How soggy is the hull? Old Glastron's are cool boats, my favorite, but were never renowned for their resistance to water intrusion/rot.

Good luck!

 

[maryhannaj]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

I received some more replies while respond to my first replies. Thanks again to everyone. This raises a few more questions.
1. What is the difference between hp rating at the prop or otherwise?
2. Will the use of 140 high comp. heads etc.. require the use of high comp 140 pistons therefore requiring machine work and a complete overhaul?
3. Would the different carb set-up require some kind of adapter kit and if so where might I find these parts?
4. Were Glastrons heavyweights in your opinion because of good design or just plain water absorbing tanks on water?
5. What are the pros and or cons for running the fins? They just came with the boat.

Thanks Bob_VT and endsapmgr for your replies as well. I have a feeling this is going to be a lot of fun...Maybe? I guess there is a first time for eveything and now it is time to learn boats. It's the first boat i have owned that wasnt propelled by oars and the rush of the speed on water was something completely different! I'm pretty sure i am gonna stick with it as long as I can squeeze out some dough for gas. And again, thanks to all!:joyous:

 

[V153]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

1) Your motor is crank rated. Meaning they achieve 115hp at the crank, not taking into account the loss due to transmitting it through the driveshaft/gearcase.

2) High comp heads or not, pistons are the same.

3) Carbs do not require any kind of adaptor(s).

4) That was a heavy model.

5) Try it without the fin'n compare your results with the fin on.

 

[maryhannaj]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

More good info . Nice fish Kbait and thanks for the cool old brochure pic V153. I am gonna find out pretty soon here just how waterlogged it is because wether it can be tuned up or not I still have a crazy need to know whats under that carpet, floor ect...I also suspect problems with the transome due to the mount bolt heads in the splashwell. They are pulling the glass inward slightly from what appears to be from the torquing over soft inner structure? On the comp numbers, a local marine tech once told me that anything above 80 or so was still good on those older Johnsons? I will run another comp test on it before i pull the motor to see if the powertune loosed anything up. Is there a rock solid comp test procedure I should follow because i dont remember that my manual offered up any such info or specified "good or Bad". Also, what is the best most effective way of winterization? Thanks everyone!

 

[boobie]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

Check the top secret files at the beginning of this forum for winterizing.

 

[Bosunsmate]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

Here it is
http://forums.iboats.com/johnson-evinrude-outboards/compression-test-jb-313963.html

Please do me a favour and add a couple of paragraph gaps in your writings as one big lot of writing pokes my eyes.
Id not buy a 80psi motor.
Anything over 100 yes so long as very even compression

 

[maryhannaj]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

Will do. Thanks.

 

[bob johnson]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

have you played with the trim while at top speed???? usually once you are at WOT if you raise the trim a littler at a time you pick up speed and rpms.....up to the point where your prop starts to catch air and whine with no power increase..... I have dropped down in pitch to raise rpms and got even more speed.....than I had with the previous prop!...but for that motor you are at an ideal rpm. i would weigh the rig on a junk yard scale and then try to figure your trailer weight( might even launch the boat and then drive the trailer over to the scale!)

you need to know if that boat is soaked with water logged foam flotation!!! you might be carrying an extra 400 lbs!....but.....43 is pretty fast...cant believe you should be getting more than that with an older motor like that

bob

 

[maryhannaj]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

It will actually whine to a higher rpm with no speed increase if trimmed full up wot. If I trim slightly back down it begins to sound as if the prop is digging back in and hit the 43 mark.
I had no idea wet foam could add that much weight either. Good to know.
I also re-checked the compression a few hours ago. Turns out it was only 109, 107, 107, 106. Not too proud of that. Time to start saving for some parts or something. Thanks Bob!

 

[Bob_VT]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

You probably will not see a return on a parts investment since your motor is not even running top compression. My V-4's (I have 2 right now) are running 120 PSI in one and 145 PSI in the other.

If you want larger carbs - you really need to have the ports machined to match that, a bubbleback exhaust also requires block machining and the spacers were just a trick OMC used to try to quiet things down.

I would advise not throwing parts on that motor for a small return and you can find a used motor (newer) faster - cheaper in the long run. You have a fishing boat - not a race boat

 

[maryhannaj]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

Understood for sure. I shoulI a have been more clear on what I mean about parts.
I meant for a clean up. . I agree with you about flushing cash on upgrades for a tired motor.
However, if I wasn't able to find something newer within my limited budget, I can go one over with still available parts from OMC.
I have been looking for slightly newer motors for a while now with no luck so far. And as for new, that just makes no sense on a boat that old. Plus, I don't think I have to tell you anything about cost.
So for now, it's what I have to work with. And, I want to be able to catch the really super fast fishes!
Thanks again Bob_VT.

 

[keefallan]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

You've got some decisions to make. You may be able to just hone the cylinders and re-ring it(don't know). The 1-5/16" carbs will make the biggest increase for you. Will the stock heads your compression should be around 115-120. With high compression heads 135/140hp, it should be 135plus.

 

[maryhannaj]

Re: Performance upgrades on 1982 Johnson 115. Any Ideas out there?

I'm gonna do some working on it today. May even take it out if it warmed up a bit today. When I do get the motor off I will open it up and have a look.
Thanks keefallan.