Volvo 5.0 GXI problem with twin engines

[MD Cruiser]

I have a 2003 cruiser with twin volvo 5.0 GXI engines. I am stumped by the problems I have been facing for the last week and a half. <br /><br />I took a four hour trip back a few weeks ago and the boat ran like a champ.<br />Last week, I took the boat out and the Starborn engine was VERY sluggish above 3000 RPMS....so much so the port engine was carrying most of the weight.<br />I checked the throttle linkage and replaced the fuel water seperater filter.....took it on a test run, still sluggish in that engine. Brought out a test gauge and the good engine was running 13.5 volts at the battery and the bad engine was running 12.5 at the battery.<br />In the middle of the week, I swapped the batteries and tried the boat yesterday. It ran great for the first 15 minutes under load, then all of the sudden the PORT engine (the one that now has the other battery) drops from 3500 completely off plane. I bring it back down to 2000 rpms and start cruising home....give it a few minutes....it comes right back on plane, runs fine and then 5 minutes later....port engine drops rpms very quickly....backfires once in a while when I try to stay on the gas and just running bad after it comes off plane.<br /><br />Today, I brought the battery in to have it diagnosed....tests out fine. I will be replacing the battery altogether and I am also planning on doing the fuel filter on both engines again.<br /><br />There were no warning alarms but the port engine has always run a little hot (need to do the impeller/ thermostat this week)<br /><br />My question....this seems like a heat related failure....if the battery tests out alright....what is going on here??? Has anyone seen anything like this?<br /><br />Where do I go next?

 

[muc]

Re: Volvo 5.0 GXI problem with twin engines

Sure does sound like you need a new battery tester.<br />Try a new battery (problem moved when you swapped them)<br />Might want to test fuel pressure next.<br />Good luck Muc