Slow Cranking

[Gatorfan]

I have Twin Yamaha F115's. The Starboard motor cranks just fast enough to start while the port motor cranks like a champ. Both motors start off the same battery (which is new). I have gone over all connections from battery to the starter and ground connection. I Ohmed the battery cables out and did not see anything that would indicate a bad cable. I swapped the starter of the slow motor with the good motor it did not change anything, the slow starter worked fine on the port motor. I checked the voltage at the starter and it was 12.3 volts before cranking and it dropped to 5.8 Volts while cranking. The other motor has 12.3 volts before starting and 8.9 volts while cranking like a champ. I have no ideas as to what I need to check next???

 

[rodbolt]

Re: Slow Cranking

both engines have problems, why would you only have one starting battery?
do a forum search on a voltage drop test.
any Idea as to the age of the engines or saltewater usage ?
but the voltage drop test will isolate the failed component.

 

[JB]

Re: Slow Cranking

Howdy, Gatorfan.

Welcome to iboats.

Voltage at the starter when engaged: I would call 8.9V acceptable but 5.8V indicates trouble in the starter high current circuit.

An ohmmeter isn't going to tell you enough. It takes only 25-30 milliohms to drop that other 6.5V.

Check voltage when the starter is engaged. . .at the battery, at each cable connection, at the solenoid input and output terminals. No one of those points should show more than 1V drop from the voltage at the previous measurement. One of them will show a 4 or 5V drop, and that is where your low resistance (low, but too high) current block is.

Good luck.

 

[Gatorfan]

Re: Slow Cranking

Thanks for the advice I found that the ground for the starter cable was corroded almost 8' back. I replaced it and it now runs like a champ.