90hp mercury runing eratic

[mudbug141poppy]

have 1989 90hp merc have not run it in over year,dumped the old fuel&put in freash added sea foam,started up idel out of ramp area,got on plane run fine then motor dropped down to 2000rpms.after awhile picked back up again,did this several times,got worried came home,what do ya think

 

[mrallen007]

Re: 90hp mercury runing eratic

Could be several things. It's worth doing some routing maintenance first. You may as well put in new plugs and a new fuel filter. Check your linkages too. I've found mine broken before. That was fun. Routine maintenance and eyeballing the motor for obvious problems may just fix it and save you time and money. Then you can start looking into the more complicated junk.

I had some similar symptoms. I found the ethanol in my fuel was eating away at my fuel lines. It was depositing black gunk that used to be fuel line in the fuel pump and filter. Thankfully the filter kept it from my carbs. You might check your fuel system for deposits like this to see if you my have some broken down fuel lines gunking up your fuel pump or fuel filter or maybe even your carbs.

Other than that, I'd check into servicing your carbs. In my limited experience, any fuel left sitting in the carbs in an off season can cause issues. They seem to be pretty finicky and often need to be cleaned and adjusted at the beginning of the season even when they ran fine before.

 

[mudbug141poppy]

Re: 90hp mercury runing eratic

have changed plugs and fuel filter,will take to lake again,hopefully sea foam will clean carbs