Compression test question

[pamlicopanther]

Hello. I recently came across a 2002 Mercury 150 at a fairly cheap price. It needs several things, but before I start spending on it I wanted to check the compression and see if it is worth fixing. How can I turn it over so I can check the compression? It needs a key switch. If possible I wanted to check this before buying a switch.

Thanks.

 

[Barnacle_Bill]

Re: Compression test question

Hook a battery up then jump the starter solenoid.

 

[Chris1956]

Re: Compression test question

Also, Let a little gear oil out, and see if it is clean, clear or shows sign of water or metal filings.

 

[Crazyman1225]

Re: Compression test question

Get a battery and jump directly to the starter.

 

[pamlicopanther]

Re: Compression test question

Thanks for the responses.

I am sure this is a dumb question, but are we talking just an unconnected battery with just one wire from the positive terminal to the starter?

I may not even have to do this though. After further observation the right head screws were a little loose. I went ahead and pulled the head. It has no head gasket. Looks like someone intended to put one in but never did. The pistons and cylinder walls look fine. No scars or anything unusual. The thermostat isn't in it either.

 

[Dukedog]

Re: Compression test question

2002 doesn't have head gaskets. Its an o-ring head motor............

 

[pamlicopanther]

Re: Compression test question

2002 doesn't have head gaskets. Its an o-ring head motor............

Thanks - It doesn't have the o-ring in it. I see where it should be but its not there.???

 

[SeaKaye12]

Re: Compression test question

heh...that's an interesting one.

For sure; they didn't take it apart for no reason; did they....

Chuck

PS. If you do end up wanting to check compression (after re-assembly ) hook up the battery normally and use a $15.00 remote starter switch at the starter solenoid to allow it to crank over with the plugs OUT and the ignition OFF.

 

[pamlicopanther]

Re: Compression test question

heh...that's an interesting one.

For sure; they didn't take it apart for no reason; did they....

Chuck

PS. If you do end up wanting to check compression (after re-assembly ) hook up the battery normally and use a $15.00 remote starter switch at the starter solenoid to allow it to crank over with the plugs OUT and the ignition OFF.

Thanks Chuck. I will give that a try - If I take it that far.

Looks like it ran hot on that side and the head was removed and they never tried to fix it. The thermostat is missing on that side too, so I am guessing it may have caused the problem.

Funny thing is everything in the cylinders looks to be alright. Nothing is cutting into the cylinders and the pistons don't have any holes burned in them or anything. There is the coloration in places on the pistons and places on the cylinder walls that you see when metal has gotten very hot.

If all these parts haven't been melted could this be usable?

 

[Dukedog]

Re: Compression test question

Pull tha divider plate and take a peek at tha skirts. One of tha main things ya can't see is tha crank and bearings so keep that in mind................. like said, loose bolts, missing t-stat. Chasin' a heat problem. JMO

 

[pamlicopanther]

Re: Compression test question

Pull tha divider plate and take a peek at tha skirts. One of tha main things ya can't see is tha crank and bearings so keep that in mind................. like said, loose bolts, missing t-stat. Chasin' a heat problem. JMO

I will look in there and see how it all looks. Are you looking to see if anything was melted? Is it possible for a motor to overheat and mess up the gasket but still not quite get hot enough to completely ruin it? The only time I had an outboard overheat was with an old Johnson 115 I had. It was no question - It burned a hole in the cylinder wall where the head attaches to it.