Ok Crazy Compression!

[UPchuck]

So to day for ****s n giggles, i Checked the compression on my 77' 75hp rude. and the results are in........ From top to bottom i got 140, 70, 140. this was checking before firing the engine. so i started er up, for a good 5-10. and checked again. Same thing, but i noticed when i pulled the plug after running, there were water dropplets on the center plug. Stuck valve right? all input is mucho appreciated

 

[guy74]

Re: Ok Crazy Compression!

Sounds like a bad head gasket, not sure what "Valve" you could be refering to. Next step would be to pull the head off and inspect the low cylinder.

 

[UPchuck]

Re: Ok Crazy Compression!

im new to this, so no valves to get stuck on a boat motor?

 

[UPchuck]

Re: Ok Crazy Compression!

could it be the rings? or could a head gasket alone cause the loss of compression?

 

[SolingSailor]

Re: Ok Crazy Compression!

No, two-stroke engines have ports, not valves. If water is getting in to a cylinder, there is likely a breach in the head gasket.

 

[guy74]

Re: Ok Crazy Compression!

X2 ^^^^^ The clue that makes me think it is probably a head gasket is the water you found, low compression and water in cylinder are good indicators of bad headgasket.

 

[boobie]

Re: Ok Crazy Compression!

X 2 Again.

 

[patrick4266]

Re: Ok Crazy Compression!

Sounds like you may get lucky and your low compression is caused by a leak into the water jacket from a bad head gasket. A easy fix if you know what your doing. Take the head off and have it tested at a machine shop to be sure it has not warped. You could do it your self if your any kind of a machanic.

 

[UPchuck]

Re: Ok Crazy Compression!

well, i got the water cover off no problem, but i got 2 bolts siezed in the head. iv soaked it with pb, with no luck, my brother in law has a spray that freezes the bolts that he said worked really well, so im gunna try that next.

 

[Ibl0wstuffup]

Re: Ok Crazy Compression!

A torch will help get it loose if the freeze doesnt work. Just be careful and put some wet rags on anything nearby you dont want to get hot.

 

[UPchuck]

Re: Ok Crazy Compression!

So. Last night i tried freeze off, and that didnt work. tried an impact wrench, heat, and finally i put the breaker bar on it. Go figure it broke. The head still refused to come off. The bolts that were froze were the ones on the bottom of the middle cylinder. so after the bolts broke, i re heated and started the drilling. got about half way thru the bolts, and hit it with the torch again. a few strikes with the dead blow and i started to get some movement, and it finally popped off. And the bolts ever so easily twisted out with a pair of vice grips. snd there was my blowout right in the middle of these 2 screws. I figure the leak caused the screws to rust and bond to the smooth throat of the cylinder head cover. But problem solved, and im thankful i didnt have to drill into the block!!!!!

 

[Sixmark]

Re: Ok Crazy Compression!

Now you need to properly chase and clean the threads for those bolts to avoid potential problems when you assemble it.

 

[UPchuck]

Re: Ok Crazy Compression!

Update:
Yesterday I ordered all my parts from marineengine.com . I ordered
thermostat
thermostat gasket
thermostat cover gasket
water cover gasket
head gasket
and a new temperature switch (what is this for) it was the most expensive at like $65
oh and an oem manual off ebay
also went to tractor supply and bought 18 new bolts for the head. (grade 8) or whatever but they are case hardened

All were in stock on their website and shipped yesterday, and im supposed to recieve them on tuesday!
Also for good measure im taking the head for a nice cleanup on tuesday! I figured I might as well or i will be going thru all this again!
I want to rebuild the waterpump, but i cant seem to find the parts on marineengine.com. Any suggestions? Its a 77 75h evinrude.

 

[BonairII]

Re: Ok Crazy Compression!

finally i put the breaker bar on it.

That's always a big "No-No" IMO. If a bolt won't loosen with a ratchet...it's time for PB Blaster and/or heat.

 

[UPchuck]

Re: Ok Crazy Compression!

Hahaha ,Yea, i tried all that and nothing worked. but its taken care of now.

 

[86 century]

Re: Ok Crazy Compression!

I would bet they have the water pump parts you need at this place called iboats.com.

 

[UPchuck]

Re: Ok Crazy Compression!

Ha hahaha . Yea i realized that last night after my post. twill have to wait another week for that.
So can someone tell me what purpose the temperature switch serves?

 

[Daviet]

Re: Ok Crazy Compression!

Makes a horn sound if your engine overheats.

 

[UPchuck]

Re: Ok Crazy Compression!

*UPDATE*
Earlier this week i put the engine back together. and all is well. i have 130 on all 3 cylinders. Took it out on the water today, and it ran better than i think it ever has, or atleast it felt that way. smooth idle, ran strong, and just sounded sooooo good! Thanks for all the help guys!