starts fine on ears but not in water

[rustybeater]

I have a 1993 90hp johnson that starts right up on the hose but when you put it in the water it takes a couple of tries to start it. Some times it will start in the water idle rough and die a couple of times before you get it going, this happens only in the water. I have heard that low compression could do this so I did a compression test but every cylinder is between 110 and 115. I was trying to find what it should be and I think these numbers should be ok. I am new to boats and do not have much experience with outboards or 2 cycle motors. thanks.

 

[BonairII]

Re: starts fine on ears but not in water

Common problem. There is no backpressure on the motor when run on muffs. Check spark quality(spark tester). When were carbs last serviced?

 

[Monte1961]

Re: starts fine on ears but not in water

Compression #s are fine. When was the last time engine had a good tune-up? Post back results and welcome to iboats!

 

[rustybeater]

Re: starts fine on ears but not in water

Not really sure when the last time it had a tune up was. I just picked up the boat about a 2 months ago. I changed out the spark plugs just the other week. I will test the spark later today and let you know.

 

[archcycle]

Re: starts fine on ears but not in water

Great thing about these older 2 stroke motors they are simple and you can put your hand on just about every component to test it. Buy a real Johnson factory manual on ebay. Not an aftermarket one like Seloc. Even the most difficult problems can usually be tracked down with using just a ratchet set, a peak reading voltmeter, and systematic troubleshooting. All of the systematic troubleshooting info is in the factory manual. Even charts of if X then check Y.

To make it run you need compression, fuel/air mix delivery, and a spark.

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