Mercury 40 HP problem....HELP!!

[SpeckWick]

Black Crow, there is a strong stream of water coming out of the motor. If the impeller was the issue, wouldn't that be noticable by a lack of water spitting out? I've only had one occassion where that happened and it was when the air temp was below freezing and I quickly turned the motor off. When I restarted it the stream was fine, and has been since.
Thanks for the help and advice everyone. I'm sure a mechanic is in my not too distant future. I will try the spark thing, replace the plugs and the bulb and hose. Can't hurt after 6 years to replace the bulb and hose anyway. I'll do the things I know I can do without breaking it, and if that doesn't work I'll give in and let someone who knows what they are doing look at it. With $4.00 a gallon gas and all it is tough to have to drop money on boat motor repair right now, but you gotta have your priorities.....right?

[fishing buddy]

My 50hp did the same thing and it was the power pack.

[crappie cowboy]

I think I may have posted about this once before, but it's back, and worse. I have a 2002 Mercury 2 stroke 40 HP with auto oil injection. When I run in low RPM, it dies or runs really sluggish. I had this issue before and was advised to idle it up, which I did, along with changing the plugs and it seemed to work, but now the problem has returned. Only now I have trouble getting it refired when it dies. I have to put the throttle at least half way(in neutral of course) to get it to start sometimes after it dies or after it sits off for a while when I shut it off to fish. Also, late in the day last time out the motor ran extremely sluggish even throttled all the way. Almost like the boat was really loaded down. I took the plugs out today and found the lower plug had quite a bit of oil on it. I cleaned it off and plan to change both along with the oil filter, but I can't figure out why they keep fouling every six months or so. Is it because I need to run a higher grade gas? Could the oil injection be adding too much oil? Not enough gas through carb? Is there a carb cleaner that I can run through it that works at all? Sorry for all the questions. I really don't have the funds or time right now to take it to the shop. If it's something short of tearing the carb apart I can probably do it. Please help.

By the way, I use regular grade gas and Pennzoil Marine XLF oil, if that matters.

Speck Wick,
You ask about changing the oil filter, I have the same motor but have not seen any oil filter on mine, ... where is it ?.

crappie cowboy

[Barnacle Bill]

Speck, you need to verify what your problem is first. Electrical or fuel? Make sure you have a strong spark at all spugs. You can do this with a cheap spark tester available from your local auto parts store. If spark is good try pumping the primer bulb when it starts to die. If it acts like it wants to pick up speed then you have pin holes in the fuel pump diaphram. With the description you give it could be either problem.

[Downwind]

Had some similar problems w/ a 90 Merc. Ended up being the fuel line from the fuel filter to carbs had broken down and small pieces of rubber had entered the carbs. Mech. said merc engines were bad about the inside of these lines deteriorating because of gasoline, especially in older motors. Mine is a 98. They have since started using a different type of line that does not break down inside.

[ky-slabseeker]

It would not hurt a thing to dump a can of sea foam in your tank and see if that helps....If you have an onboard fuel tank chances are you vent will probally located in your gas cap on the boat....

[grubby]

some of the vents on the inboard tanks are just a hose that goes to the side of the boat to a screened vent. You can disconect it and see if its pluged up. If you have indoor outdoor carpet in your boat the little pieces of that stuff can get in your vent and plug it up. If some of the pieces got down in your tank through the vent it could have your screen in the tank thats right below your gas line coming out of the tank If it has a b-nut and elbow where you gas line come out of your tank take it off and see if its open and clean. had this happen on my 85 hp and it drove me crazy until I found it. i replaced the bulb and fuel lines and still had a problem. but found it and haven't had the joy of it comeing back cause I removed all the carpet and put TUFF STUFF in it instead. Sounds like you got a gas line plugged or its drawing some air from some where. GOOD LUCK.

[hunt4crappie]

I have a 2003 Merc 40 hp 2 stroke and had the same problem. In my case the problem was the valve in the hose line bulb had gone bad. Replaced the bulb and everything was just fine. I would try this first before spending a lot of money on other things.

[Wannabe...]

I'm no mechanic, but if you can borrow a portable tank and run a new line an bulb to the motor then try it, you can either eliminate or narrow down the problem to the fuel delivery system. If it's starving for fuel, it could be a small crack in the line, or the bulb or a vent in the tank as was suggested. However, since you're fouling plugs, you may have some other issue as well.

Also, you mentioned a fuel cleaner. I use Seafoam in every tank and go through the decarb process as well. Once you eliminate the fouling issue, I would recommend you decarb it with Seafoam or something similar since the oil has not been getting completely burnt due to the problem.

Oh, and no one mentioned the fuel filter. It could need changing.

Wannabe...

[Slipcork]

Sounds like to me that the low speed jet on the carb is about half stopped up or the float is sticking open and flooding out. How does it run at WOT?


They say that a can of SEA FOAM in the gas tank is called a "tuneup in a can". Bout $8.00 a bottle and does the gas tank and motor well. Cleans the carb's as the motor is running.