1094 Mercury 75HP Compression

Joined
Feb 25, 2019
Messages
68
My Mercury compression reading are
1- 95
2- 95
3-90
4-85

Here is what has been replaced. Spark plugs, trigger, impeller, lower end oil, carb kits on both carbs. Stator tested bad but not replaced yet.

My engine runs and idles on the hose, in the lake it idles but in forward gear it will not get over 15 to 1800 RPM’s . Before I spend more money and time putting on a stator will this fix this issue or am I completely out of luck because of the compression readings?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,944
I am going to assume you have a 1984 4 cylinder 75 hp. a Serial # comes in mighty handy when someone claims to have an Engine produced in the Era when the Magna Carta was signed

Try a different compression gauge. You have all the plugs out when doing this test, and are cranking the engine until the gauge reads no higher? In addition, is the battery fully charged?

If the numbers are low with a different gauge, then pull the transfers cover off to have a look at the piston skirts and to check the Piston rings for tension
 
Last edited:
Joined
Feb 25, 2019
Messages
68
That is correct it is a 1984 the serial number is 6559264. I did have all the plugs out and the engine was hot when I tested. I also let it turn over until the gauge was at the highest possible point. I just got the gauge brand new it was the first time I used it, but it was a cheep one from Harbor Fright.
 
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