Idle surge and trouble reaching 5600RPM

[bmorebasser]

75 hp, 93 Mercury 2-Stroke,

A month ago I decided to try SeaFoam, which I poured into my gas tank and ever since I have had issues with my outboard. During idle, it will have a power surge where the RMP?s will increase by a few hundred drop down a few hundred then resume at normal. In some cases, when I put the throttle down to get on plane it will get to 5600 RMP, then drop to 4000 RPM a few seconds later. If I keep the throttle down eventually it will power surge and reach 5600 RMP and plane the boat out. It can take some time for it to reach 5600 RMP I have replaced spark plugs and changed the fuel filter since with no improvement. Does anybody know why this problem has occurred and a solution?

Thanks.

Alex

 

[Barnacle_Bill]

Re: Idle surge and trouble reaching 5600RPM

First of all 5600 is too high for that motor. WOT should be around 5000 RPM. It sounds like you have some trash floating around in the carbs. Also if its never been done you need to rebuild your fuel pump using a kit from Merc as it contains new style check valves,

 

[CharlieB]

Re: Idle surge and trouble reaching 5600RPM

How BIG a tank?

How much fuel is in it?

How much Sea Foam?

Clean the carbs, install a water separating filter, test run using a small portable tank with KNOWN good fuel in the proper 50:1 mix.