Problems with 1977 115 evinrude

[codybullard]

I bought this boat a month ago, and the first 5 or so times I took it out it would run 40mph at 5500rpm all day like a dream considering I paid $900 for it. Well last weekend I was on my way back to the ramp to go home and it bogged down no weird noise no nothing. I knew that it had to be missing so I pulled all plugs and one plug had no gap, not sure what its called but the hook on the tip of the plug was smashed all the way down. So i gap it to .040" like the other three and it runs fine for about 10 minutes and it does it again. I put another washer on the plug to back it away from the piston and its running better but tonight when I took it out it will only reach speeds of 25mph @ about 3000rpm. At first I was thinking the rod bearing was bad but its well lubricated and I figure that it would lock up if that were the case, so now I am stumped. If anyone has a clue what the deal is I would really appreciate it, sorry so long.

 

[emdsapmgr]

Re: Problems with 1977 115 evinrude

You need to take a compression check, esp to check that bad hole with the compression on the other three. You have something going on inside that cyl to damage the tip of the plug, or you have the wrong plugs in the engine..... I'd pull the plug, shine a light inside and see how it visually compares to some of the other cyls. Possible you have thrown a ring, and pcs of it have hit the plug tip.

 

[codybullard]

Re: Problems with 1977 115 evinrude

Thanks for the quick reply, I havent completed a compression check yet because I dont have the gauge to do so, but looking in the spark plug hole it looks fine no sign of anything wrong, not even carbon build up like I was kind of hopeing for. So now I am afraid I have bigger problems. How common is it and what do you think would cause me to wear out the wrist pin bushing?

 

[emdsapmgr]

Re: Problems with 1977 115 evinrude

The piston pin rides on needle bearings, as does the rod on the crank. It's more common for the rings to go in these engines than the bearings. Maybe you sucked in part of a reed.
Rent a compression gauge from an auto parts store. Once you know the compression, pull the head in question.

 

[codybullard]

Re: Problems with 1977 115 evinrude

I still havent gotten around to getting a compression guage yet...well actually I havent been anywhere neer my boat this weekend at all but I have been talking to several of my buddys about the problem I am having and everyone keeps telling me that my reed valves are deteriorating and sucking threw the engine. What are the reed valves made of for them to do this? I had never heard of reed valves until now, I had a different idea of how a 2 stroke outboard works I guess. I will get that guage this week and share what I find out, but thank you for all of your help! This is my first boat and dont know much about boats at all, and I dont trust mechanics where I'm from.

 

[emdsapmgr]

Re: Problems with 1977 115 evinrude

If a reed valve goes, it can cause the internal problem you mention. Also, you will get fuel spitting back out of the carb on that bad cylinder. Run the engine without the airbox cover and see if you get any spitting back out of the carb throat.

 

[codybullard]

Re: Problems with 1977 115 evinrude

Well I finally got a compression gauge and the cylinder that has given me problems has no compression at all. So the fun begins!

 

[codybullard]

Re: Problems with 1977 115 evinrude

after taking head off I found that piston 3 looks like someone smashed it with a pneumatic ice pick or something... the damage is alot worse than I would have ever imagined. I tried to upload pics but cant get it to work.

 

[emdsapmgr]

Re: Problems with 1977 115 evinrude

Likely the top ring let go. A common failure mode on these crossflows. The broken pcs of the top ring pound themselves into the head and piston crown, then blow out the exhaust ports. You may find ring pcs down in the exhaust cavity in the lower unit. A proper repair will involve a complete teardown. You will need at least: one new piston, 4 ringsets for sure. Personally, I would replace the head, too.

 

[codybullard]

Re: Problems with 1977 115 evinrude

I have priced a new piston, rings, gaskets for everything, wrist pin and bearings, head, and its not too bad but with the cylinder damage that I have, it might get pricey. Can I press this cylinder out? It doesnt really look like I can, and if not, about what should a machine shop charge to bore it and where can I find an oversized piston for it?

 

[emdsapmgr]

Re: Problems with 1977 115 evinrude

Check with some local marine shops and see who they use for boring. If possible, you are better off boring the factory sleeve oversize rather than pressing in an replacement standard sleeve. You can get factory (usually .030 over) oversize pistons, ringsets from any Bombardier dealer that will match identically (same weight) with your current pistons. You can run your current carbs as is on that oversize cylinder.