'79 Evinrude 115hp dies suddenly after a few minutes on plane

[Joe vandenEnden]

Hi gang. Long-time shopper, first-time poster.
All your past posts have been helpful is steering me the right direction, but I'm stuck now.
After warming up, the motor just dies after a few minutes at WOT or a half hour idling down the river. 10 minutes to cool, and runs again for another few minutes.
New iBoats coils made it start easier, but didn't fix the problem. Finer pitch iBoats prop jumps the boat out of the hole a little quicker, but same problem. Carb is soaked and sparkling clean.
Piston #3 has a ding, with matching ding on cylinder head (I understand this engine suffers from broken piston rings). Very slight leak of water through head gasket while running.
Compression:
2 (118) 1(95)
4 (100) 3(59)
Throwing a spoonful of oil in the bad cylinder brings it up to 141, but goes back down to 69 after running for a few minutes on the muffs.
Is this the right tree to be barking up to track down the engine-stall problem? The motor runs great right up until it doesn't at all. Again, it's very sudden.
Thanks for your help.

 

[interalian]

Have you checked the head temperatures? Waterpump could be failing, or a swolen water deflector rubber in the block could be blocking the water flow. Sounds like you're describing a 'hot seize'. Don't run it unless you're sure it isn't overheating.

 

[jakedaawg]

hmm, wonder where my original reply went...

anyways, if you already replaced the head gasket sounds like you are in for a bit of work. Not many easy fixes for that bad of compression.

 

[Soddy]

Our newly purchased 73 Grew with 160 hp Mercruser ran for a few minutes and then died After a while we could start again. We found crud at the fuel tank valve. We removed the tank ,cleaned it and put in a new fuel line. problem solved.

 

[jakedaawg]

Folks, he has 60 pounds of compression. Its shot. No fuel line, no water pump, no nothing gonna solve that.

 

[interalian]

^ true, but the 'sudden stall' and runs after it's cooled really sounds like hot seize. Damage has been done already. I didn't see where the head gaskets had been replaced unless extrapolated from 'ding on the piston and one on the head'. Teardown and fix or scrap it, but I'd want to know why it died.

 

[Joe vandenEnden]

Thank you all for the responses. It seems I have a winter project on my hands
Thanks again,
Joe

 

[interalian]

No Title

Look for this when you pull the heads. Good luck.

 

[Joe Reeves]

After warming up, the motor just dies after a few minutes at WOT or a half hour idling down the river.

Compression:
#1 = 95
#2 = 118
#3 = 59
#4 = 100.....

You've got a 59 psi compression reading difference between the lowest and highest cylinder reading. The engine is in the process of tearing itself to pieces. It doesn't matter what is causing it to stop running right at the present time... BUT... think....................

1 - Overheating to an extreme and seizing.
2 - Fuel pump failure.
3 - Fuel restriction.

For now, think..... Engine overhaul... OR... Engine replacement.

 

[Joe vandenEnden]

Thank you, both of you. The rubber deflectors do indeed look torn up.
I've never gone so deep as a rebuild. Is it as simple a replacing a piston and ring along with honing the cylinder?
I'm not afraid of breaking anything; it's already very broken.

 

[jakedaawg]

Thank you, both of you. The rubber deflectors do indeed look torn up.
I've never gone so deep as a rebuild. Is it as simple a replacing a piston and ring along with honing the cylinder?
I'm not afraid of breaking anything; it's already very broken.

Quite a bit more to it than that. Interalien did a good rebuild thread. Search his started topics. That will give you am idea.

 

[interalian]

Quite a bit more to it than that. Interalien did a good rebuild thread. Search his started topics. That will give you am idea.

Thanks Jake. My rebuild thread is in my signature. Don't know if photobucket still lets you see the pictures - I may host them elsewhere or embed them directly when I have some time.

 

[Joe vandenEnden]

Awesome write-up interalian. I'm inspired to grab this sucker by the nuts and give 'em a shake.
Thanks again to all.
Will update as events dictate.

 

[Joe vandenEnden]

No Title

So, two of the pistons were in super bad shape, and 3 of the cylinders moderately scored. Of 8 rings, only 3 weren't broken in pieces. Frankly, I'm surprised this thing ran at all.
Two new pistons going in, and all new rings. Honing the cylinders was the easiest job I've ever done.
Still need to buy rubber tubing to make new water diverters.
Again, many thanks to interalian for the terrific write-up. Couldn't have done it without you.
Further updates as events warrant.

 

[Joe vandenEnden]

No Title

sorry, I can't figure out how to delete this redundant post

 

[jbuote]

No expert here, and not really advising, but more a question.

I'm wondering why you're only replacing 2 pistons?
​You're already in there.. Why not replace them all and not worry about them?
​Bring the whole thing back to "New".. (Or as close to new as possible) since it's all torn down anyway.
That would probably be the move I'd make.
​
I think I might be worried (in the back of my mind) if I didn't replace them all, that I might have to rebuild again if another one goes....

​Is there something that indicates you only need to do 2 as opposed to replacing all of them?

​Again, not advising for or against anything.. Just curious as to how (and why) you chose to do just 2?
​Thanks!

 

[interalian]

Did you check the cylinders for wear before deciding what to do? If they're worn past a certain point, or tapered, a re-bore and oversize slugs are in order. As you mention it was super easy to hone, you probably didn't need to take much material out and it may be OK, but it's a lot of work and money to R&R without knowing for sure.

 

[jakedaawg]

If either of the pistons you are keeping had broken rings you are making a mistake. They must be replaced or they will break the new rings in short order. It just in the nature of the ring grooves. If they broke rings they are worn beyond reliable use.

 

[Joe vandenEnden]

Thanks guys.
After duty and import charges into Canada, I don't have the clams to replace all 4 pistons. The two already cost me nearly $500, and I'm broke now.
Still waiting for the two new ring sets, but the new pistons are already in. Not a hard job, really.
One of the pistons I'm keeping had no broken rings, and has no scars on the skirt. The other keeper didn't have a big break, and only a minor scar. If it shatters another ring, then I'll replace it I guess.
Funnily, the cylinder with the best compression had the worst cylinder scar (shaped like a ring segment, of course).
I sure hope this rebuild fixes the stalling problem. I don't have any hair left to rip out.

 

[interalian]

Pity you didn't mention you're Canadian. When I did mine last year, I got 4 OE pistons 0.030 over for C$129.95 each, which included rings and pins, from a shop in Ontario. Where are you?