Just looking to find out what the compression should be at or near for this motor. I was told by a marine dealer that the reason i am not running top speed is that i may have lost a cylinder. Was gonna do a compression test to start with.
Thanks
Matt
It's easier to ask for forgiveness than it is to ask for permission.
225 is between 100 and 110. Should be no more than 15% difference in all cylinders. Warm the motor then pull kill switch all plugs and open butterflies wide open to do test.
Richard
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kllr bee »</TD></TR><TR><TD CLASS="quote">225 is between 100 and 110. Should be no more than 15% difference in all cylinders. Warm the motor then pull kill switch all plugs and open butterflies wide open to do test.
Richard</TD></TR></TABLE>
+1
If the compression checks out ok, move on to a "Spark Test" on ALL SIX CYLINDERS.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
Appriciate the info fellas, I assume by spark test is to change the plugs or check for spark by pulling one out at a time and grounding and checking for spark?
Am i in the right ball park?
Another thing if i would have dropped a cylinder would i still be making 57-5800 rpms at WOT?
The engine does smoke alittle when started but when warm no smoke at all. When I'm running no cutting out or missing can be heard. I will start with the small and work to the bigger things.
Thanks again
Matt
It's easier to ask for forgiveness than it is to ask for permission.
"Spark test" refers to connecting all spark plug wires to a "spark tester" and spinning the engine over to watch for spark.
An alternative is to utilize a timing light.... clip the inductive pickup to each plug wire (one at a time) to make sure the light is "flashing" (less desirable, but acceptable method).
If you're at 5700-5800 RPM's.... you may have a setup, prop, or hull issue at the root of your issue, however. Very difficult to make that RPM range with a cylinder down "completely".
Still recommend checking.....
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
Mercury Parts, Mercury Outboards, Smartcraft & Accessories, Injector Service, TDR Reeds- BBC Sponsor
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