95' Johnson OceanRunner 115 runs great on land, dies above 1/4 throttle at sea.

[Ace08093]

Hello iBoat folks. I used to post here quite a bit back in the day but I couldn't remember my account info for the life of me so I had to make a new one.

So I came across a boat I got for a steal, a 19' chapparall open bow with trailer and a 95' johnson 115 OceanRunner motor. Only caveat was the motor didn't run when I bought it. I found one of the two ig. coils was bad, replaced it, and she purred on land.

Took it out to the river this afternoon and she fired up great, idle'd and warmed up just fine in the water but when I went to throttle it up in forward or reverse it would die seemingly as soon as the butterflies opened. I could sit there all day and putt down the river in gear at idle, but soon as I gave it any throttle it would just die.

Before I took it out, when I first was diagnosing the no-start, one of the first things I did was a compression test. I had 115-115-115-90, which at first seemed like one cylinder was F'd but I dumped a bit of oil in that cylinder to coat the rings (it had sat for about a year), gave it some time, cleared the cylinder of excess and tested it again and she came up to 115 across all cylinders (almost perfect).

I figured out one coil was bad, I swapped it out and she fired up nice. I warmed it up, re-did the compression test after it was good and hot and got 110-105-110-95. One cylinder, the same one, still coming in a bit low but within 15% of the others so I highly doubt that's my problem. It idle's pretty well, maybe a little rough but seems to be comperable to other motors I've heard idle.

Here's the beach though - I can start it up on land, put it in gear and it'll rev all the way up with absolutely no issue at all. Only dies under a load.... So I mean the only way I can really recreate my situation is to bring it to the water which would be a big chore if I'm just running with a trial-and-error approach.

Any advice on where to start with this? It almost seems like once it's under load the choke is stuck on, like it's just dumping fuel into the cylinder and not getting enough air... But it revs up perfectly fine when not under load.

 

[racerone]

There is something wrong.-----Take heads off for inspection.

 

[boobie]

Will your spark jump a 7/16" open air gap on a spark tester ??

 

[Ace08093]

Will your spark jump a 7/16" open air gap on a spark tester ??

yes. It's a very strong spark, I tested it at 1/2"

 

[boobie]

Squirt some premix fuel in the carb throats when it's acting up and see what happens.

 

[Ace08093]

So... Upon further inspection it looks like I have three vacuum lines that are just kind of floating about. One coming from the intake manifold on the right bank behind the carbs - the same one on the other side goes down to a fitting below the carbs, but there isn't an identical fitting for the opposite side visible. Another comes off the front of the crank case and has a T connector on it, both going nowhere and finally one seemingly coming off the top of the fuel pump area thats just kind of hanging around. I don't know how I didn't notice these before, but I'm gonna guess that's a big part of my problem. With the motor idling on muffs I plug these three lines with my fingers and the idle smooths out significantly.

So... I've been searching for about 30 minutes and even purchased a service manual from a sketchy website (was legit at least) and nothing has a damned vacuum diagram in it. Any idea where I could find a proper vac diagram?

 

[McGR]

Two of the three probably go to the air silencer - one goes over the nipple on the bottom the other slides in the hole in the top. These won't have much effect on engine performance. Not sure about the third one, pics might help.

 

[Ace08093]

Two of the three probably go to the air silencer - one goes over the nipple on the bottom the other slides in the hole in the top. These won't have much effect on engine performance. Not sure about the third one, pics might help.

I finally found a diagram for it after hours of searching and you are indeed correct. All the lines that are hanging around go to the air silencer, which no longer exists.

I found in neutral in the water it runs fine and will rev up fine, even sounds great, but in gear it will die before the butteryflies even move - soon as the timing advance starts moving it just immediately dies. Not even enough time to squirt fuel into the carbs. Not even a putter. Just running fine and dead as soon as the timing advance moves an inch.

I'm familiar with the sound a two-stroke makes when it's starved for fuel and you crack the throttle, and I was half suspecting that to be the issue until I noticed the butterflies aren't even having a chance to open. It's dead before the timing gets to full advance.

Could that be part of the problem? Shouldn't the butterflies start opening soon after the timing starts ramping up, or is that supposed to get to full advance before they start opening? I can take a video of it all working tomorrow if it would be helpful. Earlier today I mixed a can of sea foam with a gallon of gas and ran it through for 15 minutes or so. I had the can laying around anyway, figured it can't hurt might as well let it soak for a day.

 

[Ace08093]

So... I must apologize to Racerone for half ignoring his initial reply to this thread. I spent the afternoon converting a barrel into a test tank so I could play with the carb adjustments properly, swearing it was a fuel issue. After an hour of tuning I came to the realization this thing was definitely misfiring intermittently. After running the seafoam through it and warming it up I re-did my compression test and found, again, 125-125-125-95.

I pulled the head off the bank with the 95 compression cylinder and this is what I found. Clear gouging and marks on that cylinder with low compression. Sad day for me... But nobody can say I didn't try. Should have just done this in the first place but I'm a stubborn bastard.

So... I have no quarrels with rebuilding this motor. In fact I'd enjoy doing it. But do you fellas think that level of scouring can be corrected with a honing bore? I'd spend the hundred bucks or so on a good one and have no problems spending a few hours with it and a micrometer honing these bad boys out, but is it worth it?

I'm going to start hunting for part prices. Local boat shop told me about a grand for everything but they were including *everything* and, lets face it, parts house markup is ridiculous. I'm sure I can find much cheaper online. I mean really all I need are pistons and rings, assuming the crank bearings are in good condition when I tear the case apart.

So I suppose what I'm asking now is recommendations for an online parts store and recommendations on a good cylinder honing tool.

 

[racerone]

Is this day and age of computer controlled machining and inspection that -----within 15% is a joke.-----No further comments from me on this project.