1976 Johnson 115 Rebuild/Upgrade Help

[tux16090]

I am looking for some help/advice on rebuilding/upgrading a 1976 Johnson 115. I will break this up into sections for better understanding. I also do not know a lot about boats, so sorry if anything is stated wrong.

1. What I know/don't know.
I do not know what model the engine is or where to find it. I am pretty sure it has been in AZ its whole life, so just fresh water, no freezing temperatures, and a relatively dry climate, aside from when it was on the water. It had the heads pulled off probably about 20-30 years ago, but nothing else. It was running at the time but allegedly was bogging down. It is clean inside the cylinders, and the whole engine for that matter. (given its age, it has a bit of dust and oil, but looks great otherwise)

2. What needs doing
At the very least it needs head gaskets. (I don't know what gaskets to get because I don't know the engine model, if they are different from one 115 to another in the same year) I probably have to replace all the fuel lines because I am sure they are not good anymore. And to solve the bogging down issue, I think new plugs, and a carburetor rebuild. (correct me if I am wrong).

3. What I would like done
A. It would be nice to get a bit more power out of the engine, but I do not know how that can be accomplished specifically. Can the cylinders be bored out safely, and if so how much, what pistons and/or rings would be needed, and how much difference would it make? What about a carburetor upgrade? I am not sure if there would be anything else that can be upgraded within reason, or if it would make a noticeable difference.
B. It would also be nice to get a bit better fuel economy out of it if possible. I hear as it is it is/was not very good. I would plan on skiing with it, so don't know if both power and fuel economy are possible, or if that is a propeller issue.

Summed up, what head gaskets do I need? Are there any ways to increase performance and/or fuel economy. Is there anything I should look at/replace on the engine aside from fuel lines and the gear oil?

Thank you to anyone that can help.
Edit. I added some pictures of the engine, and I added some oil in the cylinders to avoid rust. And yes, I do know there is a little bit of junk in the cylinders, and I will clean it out before running the engine.

 

[Faztbullet]

Sorry but boring will not make any noticeable HP increase. That motor is pre prop rated HP and is only about 90-95 HP at propeller. You dont have trim so best option is to true heads and install gaskets. Then check compression, if good then check spark and rebuild carbs and fuel lines. Head gasket fits all V-4 3.5 bore engines...part # 318358. Only recommendation for a upgrade is to swap to newer style magnet starter as they spin a tad faster and draw a few less amps.

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[racerone]

Fairly obvious that it is a 1976 model 115 HP.-----Find yourself a 1974 to 1976 model 135 HP donor motor.---Rebuild it with WISECO pistons.---Better / less gas consumption is just not going to happen.-----A simple and rugged motor.----I skied many miles behind a 115 HP 1974 model back in the day.----A powerful beast.

 

[tux16090]

Thank you for the information. I was hoping there might be an upgraded carburetor or something like that for more power, but maybe not.

 

[racerone]

To go from 115 HP to the 135 HP you need to fit exhaust tuner ( not just bolt on ) the pieces.---Bigger bore carburetors.---Intake fillers ??--Cylinder heads.--A donor motor is the best option.

 

[oldboat1]

You are at a disadvantage if you do not know what that motor is capable of beforehand. A dirty or poorly cared for engine will give little clue as to what it might do if properly cleaned and prepped.

If this motor can be repaired for what you want to do or spend, I would go for it, then decide whether you need something bigger to suit your needs. In other words, bring it back and then decide.

 

[racerone]

So the cylinder heads were taken off 20 years ago and then the motor was set aside ???----They must have seen something.----Post pictures of cylinder walls.

 

[tux16090]

The reason it sat so long is not because the engine was bad, but because it stated getting worked on in the 90s (roughly) and then it had to be left behind because of an out of state job (not in AZ). That job lasted, I don't know, 20 years, and until recently the boat has been in a different state (AZ), and had to wait. After moving back to AZ (where the boat has been its whole life), now there is enough spare time to work on the boat and engine. Hopefully that clears a few things up. Also the boat has only had 2 owners that I know of. It was gotten in the late 70's early 80's, but has been in the family from at least 81 or 82.

TL;DR. It had to be left unfinished because of time constraints, and now there is time to work on the boat. The engine had no major issues.