sudden loss of cranking power
 

A friend brought his boat to my place yesterday said they had been out water skiing and stopped to change skiers, and nothing. Had to be towed in. I checked the killswitch, breakers, its got 12 volts to the starter. The fuel pump cycles with a turn of the key.
I'm stumped, any ideas? It's a 5.7 volvo penta,

12v to the starter remote wire when you turn the key, and 12v at the main cable connection? If you dont get 12V when turning the key at the remote wire, I'd check neutral safety switch first. If you are getting power there, and at the main post, probably the starter. Make sure the main ground at the engine from the battery is clean and tight also.

If the switched wire to the starter show's 12 volts + the main battery cable going to big lug on the starter shows 12 volts when you turn key to run

I may think that it's possibly the S T A R T E R.

LOL.

Said he had starter checked , not sure how they did that ? Told him it wasn't a starter problem but im tending to agree with you. Thanks I'll do more checking, I also did play with the shifter some but it started raining on us , so I told him to bring it back over later . Thanks
Ken

I loose (even slightly loose) main battery connection can cause this. Can be on the NEG or POS terminal. Simple check would eliminate this possibility.

Agreed with all of the above. You may try to smack the starter with a hammer a couple times to see if it starts working.

If that "fixes" it, get a starter.

I'll check all of the above thanks again , forgot about about rapping on the starter.boat only has 93 hours, so that kind of led me away from starter issue, but chit can go bad in 1 hour or 1000 . Should have listened to my own mantra at work , test it all yourself, I don't care what you tell me!

big solenoid on the front of the engine. jump across 2 big terminals. that will take out all the key, neutral switch, trim switch possibilities. if no crank, no noise and no voltage drop, starter is bad. couple of clicks, remove and clean every battery wire at both ends. block grounds especially. plus the red batt selector switch.

Have you checked the battery? It may have a dead cell.

Battery is new.
haven't had time to look at it again, and he's out of town now.
thanks again ken

Had the same thing happen on a 454efi this spring. Cranked at home but at the ramp it was dead. After lots of checking and etc it was the starter. When I got it off and checked it with a pair of jumper cables nothing happened. Dropped it on the ground to jarr it and tested again and it worked. I still put on a new one. Cheap insurance if all your voltages check out good.

:Well it turned out to be a bad relay. Another friend with much better electrical skills than me found it.