It takes 20+ times pressing the start switches to get motor to engage

[Tom Minnick]

You could always jump your slave solenoid any day this happens and you’ll know real quick if it’s the problem. Again, your description is exactly what happened on my boat. I swear some of these things are designed to fail. Ie both my IACs fail every 150 hours.

I will try this

While it is logical to assume that both would not fail at the same time, don't fall into that trap. The best approach would be to trouble-shoot one engine at a time. Maybe the ultimate issue will be something common to both engines, but I wouldn't make that a hard assumption.

thanks

 

[Tom Minnick]

Strange. Still working on problem. Had a half hour free so I went to boat to find slave solenoid but had no luck. Decided to try to start motors. Hit toggles and fuel pumps engaged. Got distracted and about 90 seconds later got to fully engage toggles and both motors started. Stayed for an hour and tried several times to start while wainting some time between fuel pump engaging and full,start and they fire up immediately or on the second push???? Makes no sense

 

[Espos4]

While it is logical to assume that both would not fail at the same time, don't fall into that trap. The best approach would be to trouble-shoot one engine at a time. Maybe the ultimate issue will be something common to both engines, but I wouldn't make that a hard assumption.

Whatever the issue, they both didn’t fail at the same time according to post #7

 

[LTD.330]

... so I went to boat to find slave solenoid but had no luck ...

A couple of ways to find the solenoids. Go to the starter and follow the wires from the solenoid up to the slave solenoid, or go to mercruiserparts.com and look at the parts diagrams for your engine. On my 7.4s the slave solenoid is located under the plastic cover on top of the engine.

 

[daddyox]

On my mercruiser 5.0 mpi this is the part. Slightly behind flame arrestor near red circuit breaker. Mine would work sporadically as well. I couldn’t predict it.