What to do next ?? Bad Compression TEST

Kleverrr1

Seaman Apprentice
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Jun 21, 2009
Messages
37
I just did a compression test on my 88 Johnson 70hp, this is what I got. I did the test with with hi idle lever up and all 3 plugs out. I got 62 on the top, 30 in the middle and 59 on the bottom. Where do I go from here and how much should I be preparing to pay to repair this problem. I was willing to do carbs, VRO, plugs, water pump, but I would think twicw before pulling pistons and all that stuff. I will leave that to the PROs if that is my last option.

Thank you in advance for all the help and suggestions
 

petryshyn

Commander
Joined
Oct 3, 2001
Messages
2,851
Re: What to do next ?? Bad Compression TEST

Try a thorough decarb and see if you get lucky and raise the compression. If the compression doesn't come up into a tolerable level, pull the head and hope for a head gasket.
Odds are good you'll likely need pistons, boring and a overhaul. $1500 - 2000 to repair it at a shop if its salvageable.

Good luck :)
 

iwombat

Captain
Joined
Jul 12, 2006
Messages
3,767
Re: What to do next ?? Bad Compression TEST

Those numbers are way low. Right now I'm suspecting either the test or the gauge. Maybe you can describe your test a little more.
 

Kleverrr1

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Jun 21, 2009
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Re: What to do next ?? Bad Compression TEST

Well the test gauge is fairly new... and here is the full story.
To week ago I had my engine serviced at my local marine shop. They said everthing was fine they told me that my comression was 85/83/84. I had noticed a small leak in the oil hose at the VRO before I dropped it off for service. They said there was no leaks and everything was good. I asked about the leakage that I seen on the lower cowl they said a little leakage is normal. I said ok great all is ready to go, 2 days later out to the ocean I go starts go at the launch. I go slow for 15 minutes in the no wake zone, once I am out to wide open ocean I do what anyone waiting all year would do. The first WOT of the season,,, what a great feeling,,,,well it only lasted about 5 minutes and it was all over dead in the water. I could not get it started to make my way out had to be towed out. Went home checked fr that oil leak because I remember seen a youtube video saying a leak in the VRO hose would cause the pump to pump oil much more often and flow the engine. So I pulled the plug soaking wet in oil. The manual choke lever was not in the correct position so I figured maybe when put the cowl back on I may have moved it, my fault. I cracked out the oil a little at a time left the plugs out for few days cleaned them change the impeller while it was down. I put everything back together yesterday put the hose on started it right ran it for 5 minute turned it of and went to start it again and wouldn't start at all.I pulled the plugs back out and the had some oil on the but not as much as before since I also made sure the hoses where tight myself this time. I did hear a small knocking nosie as I raised the idle bar when it was on so I did a compression test today and thats what I got. I will check the head gasket tomorrow because I did see a small puff of smoke some where on the block when I shut the key off. I got dark on me and will continue to accept suggestion to what I can do to get back on the water.
 

Kleverrr1

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Jun 21, 2009
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37
Re: What to do next ?? Bad Compression TEST

The test was done with the engine cold, the fuel line disconected all 3 plugs out and the gauge in one hole at a time from top to bottom. I had the choke lever up all the way on all 3 cranks which were at least 7 rotations with a freshly charged battery.

I appogize for the long posts but I really need to get back on the water.
 

tashasdaddy

Honorary Moderator Emeritus
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Nov 11, 2005
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51,019
Re: What to do next ?? Bad Compression TEST

pull the cylinder head. 85/83/84 were low, but within 10%.
 

Kleverrr1

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Jun 21, 2009
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Re: What to do next ?? Bad Compression TEST

What should I look for when pulling of the heads cover??
Will the head gasket need to be replaced after opening?? or only if needed
 
Last edited:

tashasdaddy

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51,019
Re: What to do next ?? Bad Compression TEST

head gasket must be replaced, and bolts torqued, then retorqued after 5 -10 hour running. you are looking for fragments, loose, sloppy fitting pistons. thru the flywheel looking for scratches on the cylinder walls.
 

jonesg

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Feb 22, 2008
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Re: What to do next ?? Bad Compression TEST

grab the top of the pistons and give a shake back and forth.

I'd try another compression check.
 

iwombat

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Jul 12, 2006
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Re: What to do next ?? Bad Compression TEST

Sounds like you did the test right - 7 rotations w/ plugs out should be enough. Reason I asked is, last time I had a reading like that it was a bad valve in a brand new gauge. But, the shop's readings are fairly low too. No doubt about it, time to remove the head and see what's going on.
 

Kleverrr1

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Jun 21, 2009
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Re: What to do next ?? Bad Compression TEST

Well when it rain it pours...lol I picked up the needed head gasket today just in case that is the problem. I started pulling off the head cover to see what's going on in this block. It started well 4 bolts off what a breeze, oh no broke a bolt tried a few more and removed the ones that would come off. I have 5 bolts that are stuck on there. I sprayed the frozen bolts with PB blaster for now and will let them sit untill tomorrow, I swear by that spray it get everything to loosen up. I guess I'll pull out my old power drill and left handed bit and screw extractor and prepare for a tuff day tomorrow. The shop where I purchased my gasket a 70 hp engine block with good compression in stock and for sale to replace my block if need, they are asking $500.00 for it. Wouild it be better to rebuild or swap out engine blocks. I am trying not to spend too much money on this because I hope to repower sometime late next year with a 90 hp E-Tec.
 

petryshyn

Commander
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Oct 3, 2001
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2,851
Re: What to do next ?? Bad Compression TEST

If your first post is accurate, I would buy the block. If you didn't see any evidence of water on #2 plug, $500 is not going to go very far in a marine shop to make your motor happy.
 

tx1961whaler

Vice Admiral
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May 31, 2008
Messages
5,197
Re: What to do next ?? Bad Compression TEST

Don't try to use a screw extractor on a corroded in head bolt. It will likely just break off, then you'll really be having a bad day.
 

R.Johnson

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Sep 24, 2003
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4,446
Re: What to do next ?? Bad Compression TEST

I would really suggest a repair shop here.
 

Kleverrr1

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Jun 21, 2009
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Re: What to do next ?? Bad Compression TEST

How can I remove the frozen bolt on the head I already broke one and there are 4 more that won't move at all. I don't want to break any more so I sprayed them and let them sit for a day went back the next day still nothing. Sprayed again and let sit for an other day with no result again. I was looking at my engine block and it doesn't look like it was ever opened at the head. The paint seal of black paint is un-touched, maybe since they put it together in 1988.

What kits would I need to buy to redo the complete head job??
 

rottie98

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Oct 11, 2007
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Re: What to do next ?? Bad Compression TEST

I would try an impact gun but be careful
 

jonesg

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Feb 22, 2008
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Re: What to do next ?? Bad Compression TEST

Try tightening first then loosening ..carefully.

Then try the blue wrench,
a gentle warming around the bolt then try tightening bolt first before loosening.

A machine shop can remove any broken bolts if you don't have any luck.
 

Kleverrr1

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Jun 21, 2009
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Re: What to do next ?? Bad Compression TEST

I had no luck,,, from the bolts that I did remove I can see some build up off gunk. I not rust but a thick white powder type looks like sand but cant be....I hope. I'm thinking of picking up some titanium drill bits and drilling out the bolt that broke. The others may need to drilled out too since they are very likely to end up breaking. :confused:

What kit or kits will I need for the rebuild? B/C after all this trouble I think either way I am going to do it.

Thank for all the help
 

wilde1j

Vice Admiral
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Apr 15, 2002
Messages
5,964
Re: What to do next ?? Bad Compression TEST

The white is aluminum oxide (and maybe some salt, if a saltwater motor). I'd try a little more aggressive heating, attempt to remove while still hot.
 

Kleverrr1

Seaman Apprentice
Joined
Jun 21, 2009
Messages
37
Re: What to do next ?? Bad Compression TEST

Will heating them cherry red while on the block cause any damage to the heads or the block? I didn't want to heat them before b/c I was not sure
 
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