Compression Problem 1980 25hp Evinrude E25RCSA

[maza62]

Ok, so I had my engine overheat (wouldn't start afterward) and I checked the compression and had 30psi in both cylinders. I replaced the cylinder head gasket, thermostat and seal, and the water cover gasket. The compression went up to 85psi in both cylinders after these replacements, but I still could not get it to turnover. What is next? Exhaust cover gasket?

 

[Bosunsmate]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Throw some oil in the cylinders, see if you can get it too increase compression a bit and free any rings if they ended up getting stuck.
Check for spark, as electric parts can get stuffed during an overheat, especially the coils on the hot head.

WHY DID IT overheat?
If you have dropped the LU, see if you can run it without the hose for about 15 secs, as if it is starting with no water coming in to it then you will have to suspect a leak somewhere

 

[phillnjack2]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

when you say turnover, do you mean its siezed or what ?

cant see how you done compression test if it dont turn over !!!!!!!!!!

if you mean it wont start then you need to find out what distance the spark is jumping,must be 7/16 minimum air gap.
then look at the fuel and make sure that is getting in there. pull the plug wires and keep it turning for about a
minute then check plugs to see if they are wet.
if dry you have fuel starvation problems.

just a couple of ideas to be getting on with.

phill

 

[bonzoscott]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

I agree. If it won't turn over, it's locked up. Must have seized, but yes, don't know about that compression when it's locked up.

 

[Bosunsmate]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

I think he means it didnt start, as thats what is meant by "turn over" in NZ, but we will see!

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Yes it won't start, sorry for the confusion. It overheated when the water pump broke and I didn't notice it until too late. What compression should I have?

 

[Bosunsmate]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

A bit more but it should still start on muffs at that.
Check you have spark

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

OK got my compression to 115 in both cylinders and got it to start up. But.... I can keep it running very long just dies out on me especially at low rpms. Any thoughts?

 

[Bosunsmate]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Thats excellent, a good recovery from 30psi
Check you have strong spark on all plugs.
When it dies out out try hitting the choke to see if that fixes it temporarily.
Compare both plugs after running it a few times, see if one looks dramatically different and try pulling a plug and checking if it shows one cylinder is doing all the work

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

I have a spark on both and to keep it running I have been using higher throttle. Both spark plugs look good. And yes choke helps out some of the time.

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

So, took it for a test ride and here are the problems:

-to start it up I have to have full throttle with choke on (hard to keep running), sometimes will start with normal throttle
-when running at higher rpms it will surge
-when throttle is wide open feels like it slips and the rpms go through the roof (spins out?)
-sometimes wont shift unless I either start it up in forward or I spin the propeller then shift it

Any thoughts?

 

[Bosunsmate]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Might be a slipping prop bushing or cavitation or both.
How low is the anti-cavitation plate below the hull?
Get someone to keep priming the fuel bulb at high throttle to see if fixes the surging. it might be a worn pump

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Lowered the motor a little no cavitation. Priming the bulb didn't work and still having the trouble with starting it and keeping it running.

 

[Bosunsmate]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

sounds like a slipping prop bush. you need to mark it and retest for slippage
does hitting the primer help when surging?
Have you tried keeping motor off and priming bulb to check the floats seats are not failing?

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Ok so the problem now is that in order for me to start this up I have to have full throttle and to keep it running (hard to do) I have to have full throttle as well or it will die.

 

[Bob_VT]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Your carb is clogged. The low speed passages are clogged up. Rebuild the carb

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Will do, it will be my first time with the carb.

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Ok took apart the carb cleaned it up. I didn't see anything clogged up but we will see when I put it back in if that did the trick.

 

[maza62]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Rebuilt the carb and we are good to go again. Thank you everyone for your help, I learned a ton.

 

[Daviet]

Re: Compression Problem 1980 25hp Evinrude E25RCSA

Glad you got your problem fixed, and you learned a lot at the same time.