Mercruiser starting problem when warm

[mlegrand]

1988 Sea Ray with 260 hp Mercruiser 350 GM 5.7L eng. Thunderbolt IV Ignition. Starts great and runs fine until at operating temp for about 10 minutes. Turn the engine off and when try to restart, get nothing - no clicks, no sounds, nothing. Cools down for about 10 minutes and starts great again. First happened on the water skiing, but could later reproduce at home just letting it idle with earmuffs on. Gets to operating temp, and then can't start. At times, it would start if I held the key over to the start position and waited 5-8 seconds. In-dash voltmeter will show 12 volts, but needle will sluggishly come up to 12. Have replaced slave solenoid and main starter solenoid on starter (Delco starter). After replacing starter solenoid today, started great and when at operating temp would start and stop great at first. Then it did same thing - no sound, no click, nothing as I turned the ignition to start. Held it there for 10+ seconds and still nothing. When it cooled down, it now no longer starts at all. Have not tried it cold yet. Tried 2nd battery but same problem. Beginning to suspect a bad wiring connection. Again, not starting at all now and no sound when hit ignition. In-dash voltmeter registers 12 volts when turn key on. Have not tried tracing voltage back through solenoids and starter yet. Am going to try to jump straight to solenoid on starter next to see if pinion engages and starter turns over. <br /><br />Is it possible the starter switch in dash is bad? Voltmeter in dash bad? Wiring harness not making good connection? I'm guessing the wiring harness is up under the dash - does anyone know of other wiring harness connections I should check? Am I on the right track or is there some other component I should be looking at? Starter appears to be OK since it kicks right off when it works. Hope to verify that by bypassing everything and putting jumper cable with 12 volts directly to solenoid to see starter engage. Would appreciate any experience others may have in this area or other suggestions.

 

[johnkc]

Re: Mercruiser starting problem when warm

check the main wire harness connector at the engine ,it is the large round rubber connector.in 88 i believe it was towards the front of the starboard manifold,just above the slave solenoid. wiggle it,and have some one turn the key to see if you get the engine to turn over.be careful don't get caught up in the belts and don't let the engine start.<br />it should have a hose clamp on it ,pull it apart and check it out ,put it back together and clamp it if it didn't have one.

 

[loadnet]

Re: Mercruiser starting problem when warm

MileGrand, if what JohnKC said doesn't help you, you'll have to start at the back of the ignition switch to make sure you have juice going TO and FROM the switch.<br /><br />Probe the BATT terminal with a test light to check for juice coming in (the minute the problem occurs) <br /><br />If you have juice to the BATT terminal great..<br /><br />Now Probe the SOL terminal with the key in the START position. - If the SOL terminal does not light up I would say you have a bad ignition switch.<br /><br />If the SOL does light up, you know the problem is further down the line.. so go down to the starter and probe the starter selonoid terminal with key in START position to see if juice is getting to the selonoid on the starter. If it is...you may just have a bad ground somewhere.<br /><br />Make sure your shifter is square in neutrual position while testing so to rule out your intermupter switch.<br /><br />Wiggle the shifter handle around in the neutral position while holding the key in the START position to see if she fires up.<br /><br />Remember to connect the water muffs in the event the sucker starts up on you during testing. <br /><br />PB

 

[mlegrand]

Re: Mercruiser starting problem when warm

Thanks for the good input from both of you. I picked up a good multimeter today and will work through all your suggestions over the next few days.

 

[mlegrand]

Re: Mercruiser starting problem when warm

Resolution: my father, who is not a boat guy but a great mechanic, had also flagged the wiring harness as a point of failure when looking at a schematic I emailed him. Went out to the boat cold and it would not turn over...again, no sound, nothing. Checked the battery and it was good and the volmeter on the dash was registering 12-13 volts. Just to rule out the starter, I took at portable 12-volt battery and jumped the solenoid just to hear the starter kick in - it did. Went to the wiring harness which was right on top of the engine above the slave solenoid. Took it apart. Had some oily film on the connectors. Wiped them and took a round file and filed the male and female metal connections. Put the harness back together and it started immediately with no hesitation. Let it run for 30+ minutes starting and stopping it throughout. No problems. I also noted that my voltmeter needle is sticking and not part of the problem - I tapped the glass when it did not come up and the needle immediately jumped to 12 volts with key on. Thank you gentlemen for taking the time to answer my post and for the good info.