Stumped

[Boatrookie2]

1978 Rude 115HP

Ok, here is the pic that I had a few days ago on "leakage". I was able to raise the cylinders in compression from 110% to 120%, 0% to 30%, 90% to 110%, and 40% to 60% with only putting Marvel Mystery Oil and Carbon Cleaner. It was a very good day.

Plugs are getting sparks evenly, gas is good, battery is charged, and she won't start. What kind of troubleshooting should I be doing in order to understand what is going wrong?

(It'll get right to the point of starting then just quit, very frustrating. I thought maybe blockage in fuel, pump might be bad. Filter might be dirty, something in fuel handpump line, that's about all I could come up with. It'll backfire as well but won't start.)

 

[iwombat]

Re: Stumped

Sorry to say it, but.

If those two low compression holes are your bottom cylinders, you toasted a powerhead with a lean carb. If they're on the same bank (left or right) it's probably a blown head gasket.

No way you're going to get it running right until you fix the compression problem in those two holes - whatever it is.

 

[ezeke]

Re: Stumped

Take the Cylinder heads off and inspect. Take the bypass plates off and inspect. Take the exhaust cover off and inspect.

Best case is blown head gaskets which is not likely on both sides. Next is rusted piston rings, which is certainly possible with the improvement, and even moreso when the worst compression is on the bottom. Anything else and you probably will need to tear the engine down. You might as well get to the inspections and cut to the chase.

 

[Boatrookie2]

Re: Stumped

Wow

Yep, it is the lower two cylinders that have low compression. Should I just go ahead and order to Carb kits and start the rebuild?

If rebuild, can I just honed the cylinders or do I have to re-bore and go with larger pistons?

 

[iwombat]

Re: Stumped

You've got to get in there and inspect those holes and see what's what. Let's hope for just a case of stuck rings.

 

[R.Johnson]

Re: Stumped

That cylinder with 0 compression is not going to be good. I would not order anything in the way of parts till you look at that. Then you can probably order lots of parts.

 

[Boatrookie2]

Re: Stumped

Should I just go ahead and take the whole thing apart, both sides? Or just focus on the side with the 0 compression?

 

[R.Johnson]

Re: Stumped

Both sides.

 

[iwombat]

Re: Stumped

Yep. Pop both heads and remove the lower inspection covers. Take some pictures and post them up here.

 

[Boatrookie2]

Re: Stumped

This is what I found. The cylinder with the 0 compression had the top of the piston head "eatin" up as I would describe it. Its on the cover as well. As far as the exhaust, not sure what I am looking for. But when I turn the flywheel, I can definately here suction in all three except for the 0.

I also was able to see thru the exhaust hole of the 0 cylinder that the "o" ring was broke near where the top was damaged. That could be cause for air to seap thru. But as for the smoothness of the cylinders, there weren't any dings or dents from what I could tell. What do you guys advise?

 

[ezeke]

Re: Stumped

Could you take a closer picture of the area in the circle? If not try to describe what you see. I think the water deflectors missing entirely, which may be part of the problem.

You might want to go to the BRP parts catalogs and print out the parts diagram and parts lists for your engine so we can use the same names for the different parts. You will need the diagrams for the cylinder and crankcase to start with.

http://epc.brp.com/default.aspx?brands=ej&lang=e

 

[ezeke]

Re: Stumped

If the cylinders look good, you might want to tear the engine down and see about rebuilding it. If even one of the piston rings is gone, that would be the recommendation. I'm guessing you have lost at least one piston ring and maybe part of a piston.

That's the reason for removing the bypass covers and exhaust cover. You can turn the flywheel, move the pistons back and forth and get a pretty good idea of what's up.

 

[Boatrookie2]

Re: Stumped

I would love to rebuild it. I know that i will have a hard time though but I am willing to get in there and at least try. In terms of price...I am asuming it would be cheaper that I do it myself? I know there are parts that a mechanic has to do for me like honing or boring out new cylinders. If the walls on the cylinders are still smooth, do i need a reboring or honing?

Yeah, i know what you were talking about. There was a water passage restrictor down there but it looked in bad shape. There was only a single bead down there though.

Thank you for the link, I have also a Clymers and the Manufacture's manual for the 1978 Rude 115 motor. So, I am ready to go with the dismounting. Where do I find a flywheel tool to take that off?

 

[iwombat]

Re: Stumped

Just looking at the last picture, it looks like you've got some scoring in #4. Maybe that's just the picture though. Honing isn't tough, and you can probably do that yourself. It's not going to be much to have a shop do that for you either. In order for the new rings to seat properly you will need to have those cylinders honed though. Don't skip that step! If they need bored, you'll have to buy new oversized pistons to match.

 

[Boatrookie2]

Re: Stumped

In the process of a re-build, would I need to get all new pistons and o rings or just new stuff for the 0 compression cylinder?

 

[iwombat]

Re: Stumped

Could be any of the above depending on what's worn. Best to take the block to a shop once you've got it dismantled and have them measure the bores against your pistons. If the bores are all in spec, you'll just need to replace your #4. If any are out of spec, then you can just get those holes oversized and re-bored. I'd let an outboard machine shop make the call though unless you know what you're measuring and have the tools.

BTW: They're called piston rings, or just rings. (O-rings are little black neoprene seals.) And you need to replace them all regardless of whether you keep the pistons or not.

 

[HighTrim]

Re: Stumped

Where do I find a flywheel tool to take that off?

You need a harmonic balancer puller, however upgrade the bolts to #8 hardened.

 

[iwombat]

Re: Stumped

Just thinking a little ahead here.

You might consider having a shop put together a short block for you. If you've never torn apart a lower-end, I'd sure recommend going that route. That way you don't need to fuss with bearing assemblies, rod-cap alignments, or any of that stuff. You'll still need to put the heads on, assemble the intake and install it on the powerhead.

Just a thought.

 

[Boatrookie2]

Re: Stumped

Thanks guys, I'll keep you posted.

 

[R.Johnson]

Re: Stumped

The only way you can tell if just honing will do the job is to measure. you have to measure the diameter of the cylinder, and measure the taper of the cylinder, if any. These, and other spec.'s will be in the service manual. For a successful rebuild, you must stay with in these spec.'s. Measurments are the first, and most important part of the job, and they can be quite time consuming. The tool's needed can get quite exspensive, one reason why most of these jobs' get farmed out.