2004 Mercury 225X ProMax - 255 hours - Slightly down on power, tiny stumble at idle.

**bb21xd** · 07-04-2019, 07:57 AM

Originally Posted by Greg G

Did you test your fuel pressure to get a reading?

Fuel pressure is 41 psi. Reeds are good. Going to water test in the AM.

**Hebert519** · 07-04-2019, 01:11 PM

curious as to what you would do if voltage is too high ? Im troubleshooting an opti right now and my merc gauge reads 14.1-14.2 when running

**bb21xd** · 07-04-2019, 02:16 PM

Originally Posted by Hebert519

curious as to what you would do if voltage is too high ? Im troubleshooting an opti right now and my merc gauge reads 14.1-14.2 when running

14.2 volts while the engine is running isn't too high in my opinion, I see that with trucks quite often. I think its a problem if you get above 15 volts.

**bb21xd** · 07-08-2019, 01:28 PM

FIXED! It runs great now!
Thanks for all the suggestions!
Replacing the spark plugs fixed the uneven 'stumble' at idle. Draining the fuel tank completely and replacing the gasoline with fresh 93 octane E0 fixed the top end.
Also found a slight crack in the air hose that pressurizes the oil tank.

**RSWORDS** · 07-08-2019, 04:17 PM

Originally Posted by bb21xd

Fuel pressure is 41 psi. Reeds are good. Going to water test in the AM.

41 is a bit high.

Do the VSTs in the pro max have the screen in the return like the 3 liters that likes to clog up, run the pressure high, and foul plugs?

**bb21xd** · 07-25-2019, 10:21 AM

Originally Posted by RSWORDS

41 is a bit high.

Do the VSTs in the pro max have the screen in the return like the 3 liters that likes to clog up, run the pressure high, and foul plugs?

The Factory Service Manual lists the fuel pressure range at 39-41 psi.