Still looking for some help

[rlc3854]

Mariner 75 HP, engage trasmission and throttle up the engine does not rev up except a little. In this position the engine wil every once in a while jump up in rpm's then fall back. I have an OEM service manual but it lacks a trouble shooting section. The engine wil rev up without the transmission engaged. Is it possible the prop thruster bearing is bad or the lower end gear problem. I need help with this,I wouldn't think it was that unusal of a problem.

Thanks.

 

[xjma]

Re: Still looking for some help

With the motor not running (obviously) and in neutral, how easy is it to spin the prop??

post the serial # and someone may be able to direct you to a manual with troubleshooting.

 

[rlc3854]

Re: Still looking for some help

Yes the prop spins freely. The motor serial number is 0G177761, 1994 75 HP 3 cyl. Mariner.

 

[CharlieB]

Re: Still looking for some help

Check compression and spark on all cyl's, even one dead cyl the motor will rev freely in Neutral but not have any power once shifted into gear.

Use a screw-in compression tester.

Spark must be able to arc a hot blue across a 7/16 gap when cranking on the starter.

 

[sschefer]

Re: Still looking for some help

Is the boat in the water when you're doing this?

 

[rlc3854]

Re: Still looking for some help

Is the boat in the water when you're doing this?

Yes I was on the water. The motor starts and idles fine, it just seems not able to gain rpm's. The motor does not miss or vibrate as if it was not firing on all cylinders.

 

[ezmobee]

Re: Still looking for some help

Yes I was on the water. The motor starts and idles fine, it just seems not able to gain rpm's. The motor does not miss or vibrate as if it was not firing on all cylinders.

They will run perfectly smoothly with a dead cylinder. Just won't have any power. I've experienced it myself. Not saying that's necessarily your problem but I wouldn't rule it out.

 

[rlc3854]

Re: Still looking for some help

I will run all the service tests for spark/dead cylinder. It very well could be a bad plug/coil ? I just thought that a 3 cylinder would shake like crazy if one cylinder wasn't firing. Thanks for you help guys.