crazy mercury 900

[baird]

I have a 79 mercury 90hp that runs like a top as long as its hooked to the muffs revs up idles revs in gear out of gear starts fine over and over. It does everything its supposed to like a new one until you put it in the water and then its hard to start wont idle and if you can get it to run long enough it wont hardly push the boat around. I think It might be scared of the water.any suggestions

 

[nathanhooper]

Re: crazy mercury 900

I am going to bet guys will want you to test the compression in order to give a adequate answer to your problem. I have a 1979 90hp also. Is yours distributor-less?

 

[Chris1956]

Re: crazy mercury 900

After the compression test proves the motor is serviceable, the next thing to check is the idle mixture settings on the carbs. They sound too lean, or the carbs are dirty. Have you checked the link and sync?

 

[dutchdog]

Re: crazy mercury 900

Had a Johnson that did the same thing. Check for water in the cylinders. Mine ended up being a cracked block.

 

[baird]

Re: crazy mercury 900

the compression is 125 +or - a pound on all cylinders. it has a distributer and supposidly the carbs were just checked. I do notice a mist of gas coming back out of the throat of the bottom carb when its running thanks for the help.

 

[Chris1956]

Re: crazy mercury 900

Check to see if any of the plug wies are arcing ot ground. Those older wires can break down.

They probably set the carb idle mixture on the hose, instead of in the lake. Open the top carb 1/8 turn and see if things get better. Follow with the mid carb, and then the bottom carb. Test acceleration after each adjustment. The trick is to have them set pretty rich to allow acceleration, but still lean enough to idle decently.