86 Mariner150 want run in the water

[Leonard Ray]

Took the carbs off , put them in carb cleaner for two hours and rebuilt them. Spark is good on all cylinders,drained the fuel, took the oil tank off and cleaned it and changed the oil.All cylinders have 110 or better.Timing is good.NOW when you put it in the water it will not even start but with muffs and a water hose it will run all day.WHAT AM I MISSING HERE!

 

[Leonard Ray]

Re: 86 Mariner150 want run in the water

Had the boat to two differant boat mechanic and they have no idea what is the problem is ! Number one and number four have 90 pds. compression and the rest have 110. Everything else is great. ANY IDEAS !

 

[stikboyy]

Re: 86 Mariner150 want run in the water

Will the boat try to start when in the water? Does it fire and die?

Try setting the idle rpm higher because when the boat is in the water the water creates a pressure that the exhaust has to overcome. Stemming off of this, there could also be a restriction in your exhaust passages somewhere which is creating a pressure that the exhaust is able to overcome when out of the water but unable to overcome with the added water pressure.