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merc sportjet 90 won't start in the water

nathan20328's Avatar

Join Date: Jul 2008
Posts: 2

07-14-08, 02:55 PM   #1  
merc sportjet 90 won't start in the water

My 1994 regal rush jetboat starts fine on dry land with no water hooked up (started and stopped several brief times with no problems) but when I put it in the water, it'll start, run rough, and then stall and won't start back up unless I take off immediately and even then it continues to run rough. Am I somehow getting water in the fuel and how can that happen? I'd appreciate any input from anyone out there. I-boats hasn't given me any input at all. Thanks very much in advance.


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thezster's Avatar

Join Date: Aug 2005
Posts: 2,268

07-14-08, 04:29 PM   #2  
Just a thought... when your boat is on the trailer (out of the water) the engine (which I assume is carburated rather than fuel injected) is sitting at a different angle than when it is in the water... this can sometimes affect the float angle in the carb, causing fuel mixture issues when you try to start it. That being said - it sounds like a carburation issue rather than your thought of water getting into the gas simply because the boat is in the water.

On the other hand, if there is water in the gas tank, that varying angle can also cause water (which sits in the bottom of the tank) to enter the pickup tube before gas does.

jdnsmcluer's Avatar

Join Date: Aug 2008
Posts: 8

08-12-08, 01:37 PM   #3  
Sorry just a little late! I have the same boat. Mine did the some. I found that the carb. bowl vents were pluged. I removed an cleaned the vent system. These are the three tube between each carb. on the right side of the boat. I had another boat with this exact engine do it this year too. May have to soak carbs in a cleaner over night.

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