89 150 mariner lost top end replaced burnt rectifier ran ok for ten minutes and then lost top again , but rectifier looks ok

[bluebear57]

I had issues on this motor and ran a post and got a lot of help. Got sick was not able to go out and double checking to see if what I tried had worked ,appreciate all the help, I did notice I had a burnt rectifier. It melted on the hot wire coming in when all this started my temp gauge shorted out blew out the fuse going to the rectifier the boat wouldn’t start at all replaced the fuse and then replace the rectifier Took it out yesterday for the first time in months started up ran great wasn’t 100% but it would come on up hit 4500 RPMs and after about 10 minutes It just slowly started dying shut down and it would start right up but you could not get to rebel over 1200 .I idled back to the ramp , and would stop to fish offf and on all day on all day, with same results. And then the last in was idling back to the ramp I started it up and very slowly increase the throttle and this time it would come back up to 4000 RPMs with small increments on the throttle, I had tried this all day and this is the first time it worked,took about 35 seconds to slowly get it back up there and it would run,checked the rectifier and it looks fine. I don’t know what else could be any ideas would be greatly appreciated.

 

[QBhoy]

Have you done a compression check ? Is she getting oil ? You pre mixing the oil, I presume ?

 

[Chris1956]

You can disconnect the yellow wires at the rectifier and insulate them. Now the condition of the rectifier will have no effect on the ign system.

Remember that the battery won't charge, so this is for test purposes only.

 

[bluebear57]

Thank very much for your time and response,if I disconnect the stator wires , will the engine then rev up, what will this tel me if it runs ok ? Stator or rectifier? And I just rebuilt the motor last year , got good compression and I do mix my gas and oil, Ithanks again for your response

 

[Chris1956]

If the engine runs well with the rectifier disconnected and poorly with it connected, suspect that the rectifier is shorted to ground.

The stator charging coils and the stator ign coils share a common steel core, so they are capable of influencing each other's behavior.

 

[bluebear57]

If the engine runs well with the rectifier disconnected and poorly with it connected, suspect that the rectifier is shorted to ground.

The stator charging coils and the stator ign coils share a common steel core, so they are capable of influencing each other's behavior.

 

[bluebear57]

W which one would cause the motor to lose top in power. It all started after the fuse blew to the rectifier I replace a rectifier and it ran pretty good about 10 minutes and then lost top in again. Would you think rectifier or stator ? Thank you

 

[bluebear57]

I can only run with water muffs right now , but it runs the same thanks would a bad stator cause the condition I described? Thanks

 

[Chris1956]

Do you have spark to all cylinders? That motor has 1 stator, 2 switchboxes and 3 triggers. The stator has both low speed and high speed windings. I believe the stator switchover to high speed windings is about 2000 RPM. You will therefore need to test spark at high speed as well.

Lost spark to 3 cylinders may indicate switchbox failure. Lost spark to 2 cylinders may indicate bad trigger.

Obviously at least part of the ign system is good.

Also check the wiring. Melted wires can cause shorts to ground.