1995 mercury 200 XRI efi 2.5 liter compression test low.

[NC bass fishing]

I have a 200xri efi serial#0G146366 that I just did compression test on and all cylinders tested 85# give or take a psi. The engine was warmed up and at work throttle is there anything else to check for cause for low compression or just time for rebuild or new powerhead.

[EuropeanAM]

Fully charged, good, amply rated battery connected?

ALL spark plugs removed from the engine?

Repeated the test with a separate, known-accurate compression gauge?

Tend to suspect one of the above may be the key.

[NC bass fishing]

Full battery and all plugs removed but it is cheap tester from harbor freight going to get another tester to verify results

[jtipton91]

Thats your issue. Mine was low on harbor freight gauge. Good compression on a rental gauge from auto parts store

[NC bass fishing]

I bought another compression tester from O'Reilly's and compression tested 115psi on #1 and 120-121 on other five cylinders. Been having idle issues and just checking everything to find what the issue is. Going to do link and sync once the dial indicator I ordered arrives have already replaced stator,trigger,voltage regulators and coils and plugs. Tested spark on all cylinders with 7/16 spark gap all good. Also found bleed system filter plugged and replaced it.

[NC bass fishing]

I ran compression again with snap on compression tester that borrowed from mechanic friend and pressures were 125-127 on all cylinders. I think I may have found idle problem ran boat on portable tank and it idle dead steady then hooked up on board tank and it started idling badly again after a few minutes then hooked back up portable tank again in a few minutes dead steady idle again. Looks like need to empty main tank have some bad fuel thanks.

[leonreno]

Also check the fuel lines, they may be failing on the inside.