1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

[phillnjack2]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

well while youve got it that far down i would rebore the whole thing and fit new pistons and rings ,new mains,new big and small ends
and check the conrods have not got any bends in them.
Have the crank measured to make sure its true, and fit new seals etc everywhere.
you have to realise this is gonna be just like a brand new motor when finnished and will last you a long time if kept well lubricated and cooled.
Its 30 years old now, so expect a lot more years from this engine once all done nicely.

Youve been lucky as in no broken bolts, that already has saved a lot of time and money.

keep the pictures comming, its good to see rebuilds done in pics.


phill

 

[Faztbullet]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

If any of the cyls two are too out-of-round (beyond factory tolerance) you will have to have those two cyls bored .030 over

just a note...you dont have to bore .030 as you can get pistons from .010 -.064 oversize, go with the smallest oversize that cleans up the bore.Also mike the good cylinders to see if they are past wear limits or out of round as these cylinder wear in a taper and around intake/exhaust ports due to side thrust.Mike the pistons too as the life/performance of a 2 stroke is the skirt of piston along with rings...

 

[dicarlo]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Do any of you have the specs on this engine? (What the tolerances are for the cylinders) I ordered the service manual but it wont be here until next week. Id like to get the head to the machine shop Monday.

Also by boring and going to bigger pistons is that going to gain me much in the means of power?

 

[Faztbullet]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

What the tolerances are for the cylinders

3.500 is standard bore and anything over 3.503 is worn and needs boring........

Also by boring and going to bigger pistons is that going to gain me much in the means of power?

Maybe 1-2 hp.....

 

[GeneH]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

I like to get an engine completely torn down and measured before sending anything to the machine shop. That way there are no "surprises" later on. You could discover the crank is bad. What do you do then? It may change your direction. Good luck!

 

[Joe Reeves]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Completely torn down is standard procedure.

 

[dicarlo]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Everything has been torn down. It all came apart nicely with ease! No broken or stripped bolts either! Just dropped the head off at the shop to get the cylinders mic'd up and then I will order pistons and all the parts. Hopefully its not too messed up and can be bored.

Wanna get this thing back together soon!!!!!


Ill post pictures during the rebuild. But the main problem was the over heating from the water deflectors, and seeing that this is not so uncommon.

 

[dicarlo]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Completely torn down is standard procedure.

So got a call from the machine shop today. They say that is needs to be bored .040 over. Is this possible for this engine? I am having trouble finding pistons larger than .030 over.

I didn't see anything specifically about this in the service manual.

 

[rolmops]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

You should ask the machine shop people if they can resleeve.

 

[Joe Reeves]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

I am having trouble finding pistons larger than .030 over.

Check with WISCO

 

[dicarlo]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Check with WISCO

Talked to Will at Premiere Marine in Orlando today. Great guy! Stocks them and has a great price. The shop ended up wanting $110 per hole for boring...that is more than double most other shops. Looks like this project is gonna take me longer than I hoped. Hopefully bringing it to the guy I should have in the first place, bit of a drive but shoulda did it to begin with!


REBUILD SOON!!!!

 

[Faztbullet]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Personally I would not use a Wiseco.... You can get rebuild kits for that engine if you shop around. The kits I sell have all the internal bearings for crank, rods, piston and the pistons and gasket set and pistons are cast like the OEM pistons. I use/sell these kits all the time and never had a problem on any, just wish they carried more Etec sizes....

 

[Joe Reeves]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Personally I would not use a Wiseco.... The kits I sell have all the internal bearings for crank, rods, piston and the pistons and gasket set and pistons are cast like the OEM pistons.

I find that strange. Having been a serious minded mechanic for many years, the last fifteen of which were in the Tampa Bay area (retiring in 1991), I found the Wisco pistons to be of top quality all around. The many engines that I rebuilt were always received satisfactory by my customers with never a comeback.

The Wisco pistons did however (at that time) require a four (4) hour idle break in time which if ignored might create problems. However, I stressed this requirement upon my customers who adhered to that one inconvenience. Whether that requirement is still in effect, I have no idea.

 

[Faztbullet]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

The Wisco pistons did however (at that time) require a four (4) hour idle break in time which if ignored might create problems.

Still have to let em go thru several heat cycles to temper up as the forgings are soft, on a crossflow the cooling system must be in tiptop shape
for these to temper properly and takes about 6 hours to do properly. The molly coating they now apply is for break-in purposes and is gone in about 2-3 hours...

 

[V153]

Re: 1980 Evinrude 100HP - Low compression on 2 cylinders. Need help

Never ever had a problem with Wisecos. You just gotta correctly perform the break in ceremony ...

 

[Maschine]

I found this thread and I also have the same situation. I removed the small window on the side of the engine. It allows me to see the Piston and the rings. The psiton is in good condition. It moves nicely and the crosshatching on the cylinder sleeve is visible.

I am unable to move the rings so I am assuming they are stuck... I've oiled them and will see if they loosen up. We did have good compression before we attempted to fix a lower unit issue with the rear shift ( oil pump ). But now we have 60 on cylinders 1 and 3 ( port side ).

I removed the Cylinder head, and the gasket is new. I did notice, the bolts came off rather easily. I am thinking they weren't torqued.

Anyhow - stuck rings - worse case scenario, tear it all apart to get to pistons ? ( its a shame as the engine ran well )

MODERATOR EDIT: Please review the forum rule about posting to old threads and avoid piggybacking your issue to an existing thread. It is best to start your own thread.

 

[brodmann]

You're tagging on to a thread from 2012. You probably need to start a new thread. You lost compression as a result of fixing a lower unit issue?? Did you remove the power head to address this lower unit issue? The gasket that goes between the powerhead and mid section could have been damaged and it would cause this problem. The rings are compressed when they are in the cylinder. You can't move them when they are compressed in the cylinder.