I have twin 502 Mag MPIs in my Formula. Today after a lunch stop when I went to accelerate the port motor hits 3000 then starts falling back like ignition loss. Then I noticed that it did it when the strbd motor hit 3500. So I switch the batteries from ALL to 1 which effectively gave each engine one battery and the problem went away, but it seems like the stbd engine is about 100-150 rpms weak?????? Anyone ever seen this before? BTW, I have always run the batteries on ALL and it has worked fine till now.

Can't help much with your mystery but running on both is not good. Even two brand new batteries will not be totally alike, so the weaker of the two will be seeking a charge and the good one will be getting slightly over charged which in time will kill the good battery.

Phil

ttt

Ted,
as your looking at the switches, rune the left one on 1 and the second one on 2. Thats what Carl told me to do when he hooked them up. any questions call me...Rob

More info on the subject.

Dave

Ditto on what Dave has posted. Now I would check altinator voltage output at the back of the altinator.

John S.

Cool thanks for the info guys, must have missed that one

Both my dash gauges (Livorsi) show 13.8-14 volts when humming along so I don't think voltage is the issue. After Rob's post I suppose I should remove the switches and trace the wires to each battery to see how it's wired. Hope I didn't smoke anything by running on "both" for all this time. This is the first time in about 10-15 hours of operation that anything acted funny. Maybe the right motor seeming to be down 100-150 is just the tach??