cooltoys61

Just a real stupid question here. Is it possible for a bad batt(maybe bad cell) to prevent one motor from getting enough juice. I tried to start by switching power from both batts on the selecter to that motor but it would barely turn, I had to retard the timing to start it or limp home on the other. Other motor spun well. Guess it's the starter,,it would be the one on the inside.

Edward R. Cozzi

Had a Cigarette 38' with the same symptom.
After much fooling around it was the ground cable at the bellhousing from the battery.
How does it turn over cold?
Some bad starters work okay when cold.
Isolate the battery and load test it.

SmallPP

Easiest battery load test is to measure battery voltage at the terminals during cranking. Should not drop below 9.5 volts. If it does, shes pretty tired with not much reserve capacity left. Yes check all cable ends. You can also do a quick check by using jumper cables from the battery negative to the engine for a quick check of bad ground. If you are changing starters, try to use the smaller body late model permanent starters. They are much more powerful, lighter, quiet, and use less current. Plus, they are OEM in later applications.

88Fount33

This being my first twin, I tried to start my starboard engine from my port battery, it would not hardly turn over. Later found out here that my boat did not have a block to block ground wire (heavy duty starter type). I installed this and now either battery can start either engine, no problem. My old Fountain is like two totally isolated engine/drive/fuel systems with the only common link being the battery selector switch. The way it was explained to me was I was trying to draw starting current through the 10 gage accessory equipment ground, had to have the complete high current path to the "other" battery.

Lmarth

Not a stupid question at all! I had a similar problem last summer where the first engine I started would turn over slow and then pick up speed and start. It acted just like a BBC that had come up to temp and had too much initial advance. The battery selector switch had both batteries connected together to start either engine. I believe I inputted to a post on this kind of problem with all the particulars. I can't remember what the static voltage was for the two batteries, but I do remember that when I load tested the batteries, one had essentially no voltage output (bad cell). I'd make sure all connections were clean and follow Ed's suggestion to load test the batteries and go from there to the starter,etc.If wired together, a bad cell(s) in one battery could pull down the other. In this case, one motor spins fine so I'd follow the sequence I've outlined and look at connections to that starter and load test that starter.Let us know what you find. Lou

Lmarth

At the risk of beating this to death, I went back and found the thread I referenced in my post on this topic. It was "Extra Battery" dated 8/19/04. What was interesting was that with the two batteries in my boat connected together, A meter showed 12+ volts statically on both batteries even though one had bad cells. When I removed both batteries, the one with the bad cells showed only 6 volts and virtually nothing with a 50 amp load on it. Point is to make sure each battery is isolated when ya check it. For what it's worth...