'77 Mercury 1500 Compression Test - #6

[Kargh]

Compression tested 1-5 today. All read between 128-135 but I cannot possibly get to #6.I have the OTC 5605 Deluxe kit and the ends on the hose don't spin freely (not sure if they are suppose to or not.. didn't want to mess them up by trying to force them). How on earth do you test #6? Is there some sort of adapter that I don't know about?

I've looked around a bit but I've not found any mention of anyone having that same issue.

 

[Texasmark]

Okaye, let's be practical. Numbers 1-5 are right where you want them. Any reason to suspect #6 wouldn't follow the pattern? Plug look the same as the rest? Flashlight and mirror looking into the spark plug hole, with the piston all the way up, does the crown look like the rest? If so on both counts, I'd button her up and be on my way.

 

[3rdtimesthecharm]

You can get a stubby compression tester on oldmercs.com. It should work in that area.

 

[Kargh]

Okaye, let's be practical. Numbers 1-5 are right where you want them. Any reason to suspect #6 wouldn't follow the pattern? Plug look the same as the rest? Flashlight and mirror looking into the spark plug hole, with the piston all the way up, does the crown look like the rest? If so on both counts, I'd button her up and be on my way.

This was my assumption but... I also like to be thorough. Its not doing anything that seems to indicate any sort of issue -- I just wanted to make sure that I wasn't completely stupid and missed an obvious way of accessing that one.

 

[Texasmark]

This was my assumption but... I also like to be thorough. Its not doing anything that seems to indicate any sort of issue -- I just wanted to make sure that I wasn't completely stupid and missed an obvious way of accessing that one.

Over the years I always had problems with the lower cylinders and the cowling. On Mercs, back in the 50's it was the upper and lower cylinders on the classic 4s. The top cowl was bolted on and only the midsection clamshell came off unless you found a fancy gauge or unbolted it. Back in the 70's I had an 850 and the upper cowl was removable. Much nicer.

 

[Chris1956]

Probably #6 compression is fine. That is usually the case. However, I just install a 90* brass elbow with the correct NPT thread between the compression gauge and the business end of the gauge, and I can then get to all 6 cylinders.

The second choice is to unbolt the cowling support (6 bolts), remove the fuel line from the pump, and remove the lowest piece of cowling (4 ss screws), and maybe the rectifier wires, and push the lower cowling down to expose the #6 spark plug hole.

 

[Texasmark]

Probably #6 compression is fine. That is usually the case. However, I just install a 90* brass elbow with the correct NPT thread between the compression gauge and the business end of the gauge, and I can then get to all 6 cylinders.

The second choice is to unbolt the cowling support (6 bolts), remove the fuel line from the pump, and remove the lowest piece of cowling (4 ss screws), and maybe the rectifier wires, and push the lower cowling down to expose the #6 spark plug hole.

That's a hell of a lot of trouble to be a purist on a pretty much sure thing in the first place. But it's not my call so why mouth off at all? Because that's how I feel. Yeah but it's not your engine. Humph!

Good luck whatever you decide.
Mark

 

[flyingscott]

You need to check #6 I have a 90 hp tohatsu in my shop right now compression on #1 is 130 #2 125 #3 25 not a typo 25 psi on cyl #3. Go to the auto parts store and get the parts to make a 90 deg adaptor for the tester.