Mercury 90HP Saltwater Edition (2-stroke) starts but won't run

Hi, this is a question about my 2003 Mercury 2-stroke (3cyl) 90 HP Saltwater Edition.

My boat has sat idle for the past couple of years and I tried starting it last spring with old fuel. It started and quickly died. This happened several times and then the battery gave out. I charged the battery and put her back to sleep for the summer.

The stripers are running, the bathroom renovation needs to be finished, and I need a day off. I tried starting the boat again, with new fuel this time, and I'm experiencing the same thing. She starts, with choke, runs for a few moments (maybe fifteen seconds) and then dies. I generally don't like to use the throttle when starting boat engines but I've tried in this circumstance thinking it may help move the old fuel out. Same thing, except with the throttle and some adjustment I can get her to run for almost half a minute or so, then she dies.

This engine has always run great and I think I hurt it by trying to run it on the old fuel last spring.

I think I've run through this starting procedure enough to get the old fuel out. What's next?

I'm looking for the simplest step here as there are too many other chores in the way of a major repair. Any quick checks or possible solutions you can think of would be fantastically appreciated.

And no, I'm not going to take it to the mechanic... yet.

Thanks,

Dennis

You will need to remove the carbs and clean them. That is going to be your starting point and 99% of your problem.

Big mistake trying to use old fuel! Now comes the $$ and effort to correct that. Sorry.

Jeff

Looks like you are going to have to pull the carbs and clean.

first & easiest place to start-pull drain plugs on carb bowls-spray a carb cleaner into bowls really flood it-do this several times-replace carb bowls plugs,pump up fuel bulb & start-this worked for me on a 40hp mariner-then by marine type STABIL & treat gas in tank assuming it's still fresh-use stabil year round if this fixes problem

Well, looks like my worst fear is met. Clean the carbs seems to be the only option. Looks like I have a winter project... another. Ha.

Will keep you posted on the progress.

Thanks.

Dennis

While I doubt this will be the only issue, you may find that part or all of your fuel hose/pump bulb has deteriorated and needs replacing. The carbs are highly likely to also need a good clean.

I just ran across this old thread and thought I would follow up on it. Rather than pulling the carbs I decided to begin less intrusively and started with the suggestions of Chuckwill00.

I drained the carbs and then sprayed them inside thoroughly with either Mercury carb cleaner or Marvel Mystery Oil. I really cannot remember which. (I know I bought the Mercury cleaner... I just can't remember if I used it right off the bat... probably). I covered it all back up and let it sit for a couple weeks. The old fuel was dumped into the car and I started with a fresh batch of Premium Octane treated with Marine Stabil. I started the engine several times and as before it would start but not run. I started the engine enough times to make sure the new fuel was thoroughly mixed in the carbs and put her back to sleep. I let it sit for another couple weeks and tried again. This time I got her to run on the third or fourth try and have not had a problem since. This was a couple years ago and the engine continues to run beautifully.

So if you are experiencing a starting problem where old fuel has been part of the mix, I suggest taking your time and letting some cleaners do the work they were designed for. Pulling perfectly good carbs apart was never a high priority on my list of things to do. I'm really impressed at how the carb cleaner and stabile resolved this problem. This engine continues to run so well out on the water it's unbelievable.

As Wynjim55 mentioned I did need to replace the exterior fuel hose and bulb as well. They simply deteriorated from what I assume was weather and UV rays - not sure if the fuel was a factor here or not.

Dennis