Troubled Merc

[fishbonez]

Ok fellas I'm reaching the end of my funds and any advise is appreciated....Here's the low down: I've got an 03 Mercury 90hp saltwater series ( and dont say "well..there's your problem) that had been running fine. I'll try to keep it simple here. I got a standard service done (plugs, filters, impeller, water separator, etc.) first trip out it lost power. Almost like i had chopped the throttle back even though it was wide open. I can usually make it out from Shields ramp to about the first stake before it happens (so say 20-30 min run time). I can shut it down and play for an hour, fire it up and its still in the same "slow mode" condition. I'm usually forced to come back in at about quarter throttle speed or less. And always at some point headed back I'll shower down on it and the motor will respond like no problem was ever there, I've always come back with full power.

Had the carbs cleaned....it was no cure, there was water in the tank...it was siphoned off and problem is still there. I will say the problem was progressively getting worse, powering down sooner and for longer periods until the water was drained. I was able to get to the second stake before it happened again, but it still continues to do the exact same thing every time.

The primer bulb doesn't ever flatten out, it idles fine, pisses fine and oils fine while in this lack of power mode. its not an overheat issue and the fuel and oil pumps are fine.

If it was something electrical it has to be and intermittent problem, and most electronics don't go from good to bad and back again...right? What kills me is the motor is afflicted on the way out and cures itself sometime on the way back in....every single time. After putting a grand into services so far, I need to keep these guys in check and try to narrow the focus to get the best use of their time.

Anything helps...lets hear what ya got to suggest

[tin can]

I would suspect something in the ignition system. I can assure you, from past experience, a bad electronic part will cause an intermittent problem.

If it is one if the electronic ignition components, diagnosing which one is a problem. The mechanic can't test for the bad part until it fails. If the motor won't act up, he can't fix it.

I don't know who's been doing the work, but I can tell you Fred, at Parkway Marine, is familiar with the problem.

[FUTCHCAIRO]

WHAT T.C. SAID, I WOULD STILL BE SUSPECT OF A WATER PROBLEM SINCE YA HAD WATER ISSUES BEFORE.
PA

[MudDucker]

I had a very similar problem. After mucho money, the guys in Lake City figured out that the mechanic at Mike's Marine in Panacea had removed the oxygen sensor for cleaning, but had not replaced the $3 foam gasket. The gasket was leaking and fouling the oxygen sensor. Good luck!

[What a mess]

I got a used motor for my boat when I first tested it it would go into low speed safety mode I thought I had bought a bad motor, in my case the prop was wrong and as I trimmed up it would over rev and a limiter would kick on but mine had an alarm that sounded when it happened since the I had them reshape my prop at Gator and it is doing fine. It does not sound like this is your problem but maybe that will help someone else along the way. Is a limiter coming or is it just crapping out?

[procraftwes]

I had the same problem with my merc.. turned out that the power packs were going out so it would run great for about 30 min then went into limp mode..from what i was told mercs have 2 power packs and they usually dont last for more than about 4 years.. im not saying its your problem but id at least do a spark test it sounds ignition related..

[fishbonez]

Thanks for the suggestions. I was starting to think it could be an ignition problem like a bad coil till I had Shields take a look and they found the water in the tank. They pumped out the water and ran to the light house with no problem. I hate to pay for a joy ride, but I know if they run it out longer they will encounter the problem, like T.C. said they cant find it if its not acting up.

[What a mess]

Do you belong to a vessle towing service? Great time to join may save some coin.

[Steve Stinson]

I second the Procraft"s vote above for the power pak. I had a 115 hp Merc do the same thing to me years ago and the symptoms were exactly as you describe. You can tell the difference between a fuel problem and an ignition problem by the way the motor acts when the problem is occurring. A fuel problem will most likely surge and change rpms more gradually. Also, you can normally make the symptoms change by pumping the fuel primer ball while under way.

Ignition problems tend to shut down cylinders, which changes the rpms more suddenly.

Hope this helps. - Steve Stinson

[Natureboy]

It's a Mercury cuz, that's your problem! Slap a Yamaha on the back and go fishin"

[Hula Popper]

I once had a Ford pickup that did exactly that -- ran fine, then started starving for gas.

It took me weeks for figure it out. I had picked up some bad gas -- had water and other junk in the tank -- and a piece of crud -- a small chunk of rubber -- had gotten sucked from the tank to the fuel line.

The rubber would float up the line to a wide spot -- a section of hose that connected two brass fuel lines -- when the truck was stopped. Then the truck ran fine, if it sat parked long enough.

But once you drove it a few miles, and as fuel moved through the line, the rubber piece got pulled down into the smaller diameter brass line, where it blocked the flow and starved the engine.

Ran fine, then sputtered. Stop the truck, fool with something long enough, and truck ran fine. Then sputtered.

It was only by accident that I discovered the probem -- I was taking off the gas tank to drain it and I removed the section of hose. The piece of rubber fell out.

Truck ran fine after that.

So, maybe when you got all that water in your tank you also got something else that is blocking the flow of fuel after you get underway.

[MudDucker]

It's a Mercury cuz, that's your problem! Slap a Yamaha on the back and go fishin"

The problem I described was with a Yammy. Overall though, I would rather go grey than black.

[procraftwes]

i would make sure you had the carb bowls drained of the water that was in the tank.. or just take it to porter marine they do awesome work..

[cmccord]

I have had a similar problem on a Johnson in the past. However, the problem was not with the motor, rather it was with the fuel/water separator (fuel filter). Even if teh water was siphoned out, there may have been enough to bother the filter, or it could be full. That is a relatively cheap test fix. Good luck, I know that problems are no fun at all.

[reelbad]

You also might want to take a look at the check valve where the fuel line comes out of the gas tank, that ball can stick and cause the gas to not flow like it should. Mine was bad on a 150 Merc. Good Luck.