Merc 5.0 falls on its face

[carrollcountybuckhunter]

Hello all, I'm new here so bear with me. A few months ago I became and owner of Wellcraft 210 Classic. I've finally had the time to take it out on the river for a shake down. It's ran great on land other then a low idle. Today we left the dock and after clearing the no wake zone I shot the gas to her. She rolled up on plane but spit and sputtered and fell flat on her face. At 3,000 RPM she would run kinda ok but dropped on its face anything above. I managed to pull the screen/strainer out of the carb and it looked good. It does have a canister fuel/water filter on it as well but I was unable to get it off to have a look. We closed it all back up and gave a few more tries and it did one time run over 3,000 at 30MPH but had a noticeable miss to it and soon feel on its face again. Put it in neutral and it will rev fine and dandy but as soon as you put it in gear and put a load on it, it falls flat. We anchored up and salvaged the rest of the time with some swimming. On the way back in I couldn't go even at half throttle or it would stumble and stall. We did notice one side of the exhaust (dry exhaust) seemed to put out more smoke or steam then the other. Not sure what's up with that since that's where the water dischargees. I'm kinda thinking to pull the filters, and plugs to have a look but the steam or smoke issue has me worried a head gasket is blown.

Any ideas on what you guys think is going on ? Any help or info will be greatly appreciated.

 

[alldodge]

Hello all, I'm new here so bear with me. A few months ago I became and owner of Wellcraft 210 Classic. I've finally had the time to take it out on the river for a shake down. It's ran great on land other then a low idle. Today we left the dock and after clearing the no wake zone I shot the gas to her. She rolled up on plane but spit and sputtered and fell flat on her face. At 3,000 RPM she would run kinda ok but dropped on its face anything above. I managed to pull the screen/strainer out of the carb and it looked good. It does have a canister fuel/water filter on it as well but I was unable to get it off to have a look. We closed it all back up and gave a few more tries and it did one time run over 3,000 at 30MPH but had a noticeable miss to it and soon feel on its face again. Put it in neutral and it will rev fine and dandy but as soon as you put it in gear and put a load on it, it falls flat. We anchored up and salvaged the rest of the time with some swimming. On the way back in I couldn't go even at half throttle or it would stumble and stall. We did notice one side of the exhaust (dry exhaust) seemed to put out more smoke or steam then the other. Not sure what's up with that since that's where the water dischargees. I'm kinda thinking to pull the filters, and plugs to have a look but the steam or smoke issue has me worried a head gasket is blown.

Any ideas on what you guys think is going on ? Any help or info will be greatly appreciated.

Howdy

Yes pull and replace the filters, all of them including the one in the carb.

Next replace the raw water pump impeller. The impeller is inside the outdrive and the drive should be removed to do this.

Lastly, for us to be able to help you correctly we need to know the engine serial number or at least the year

 

[carrollcountybuckhunter]

Not sure of the serial number but the motor is an 1988.

 

[alldodge]

If you have a hew design fuel pump it will be the one in this link. Item 2 is your fuel filter
http://www.mercruiserparts.com/Show...0&bdesc=FUEL+PUMP+AND+CARBURETOR+(NEW+DESIGN)

If you have the older design fuel pump it will be in this link and filter is item 3
http://www.mercruiserparts.com/Show...0&bdesc=FUEL+PUMP+AND+CARBURETOR+(OLD+DESIGN)

Looks like there is not a filter in the carb, and you should rebuild the carb if the filter does not fix your issue

 

[Maclin]

If it has points style ignition then it just may be time for a tuneup.

 

[carrollcountybuckhunter]

I'm pretty sure I have the old style pump. I managed to disconnect fuel line from carb and inspected the thimble sized screen/filter. It looked fine. I'm gonna pull the spin on fuel filter off this week and have a gander at that. It does have a points style ignition on it. The guy I got it from claims the motor has been rebuilt and only has around 250hrs on it. Thanks for the advice and let me know what else I could check. Maybe I'll post a few pictures of what I'm dealing with. There's also a reset button near canister fuel filter. Looks like it's wired up to circuit breakers. Not sure what it's for.

 

[Redwing4900]

I had this exact issue with my '88 3.0 liter a couple of weeks ago. The clear hose connected to the carb was filled with gunk which made me wonder how it got there. When there is fuel in that clear hose the fuel pump is bad. I pulled off the clear hose cleaned it out, then disassembled the fuel pump and cleaned out more of the same gunk very carefully with some wd40 so I wouldn't ruin the diaphragm. Put it all back together now she runs perfectly. Check your fuel pump my humble opinion. Good luck!

 

[thumpar]

I had this exact issue with my '88 3.0 liter a couple of weeks ago. The clear hose connected to the carb was filled with gunk which made me wonder how it got there. When there is fuel in that clear hose the fuel pump is bad. I pulled off the clear hose cleaned it out, then disassembled the fuel pump and cleaned out more of the same gunk very carefully with some wd40 so I wouldn't ruin the diaphragm. Put it all back together now she runs perfectly. Check your fuel pump my humble opinion. Good luck!

The clear tube has nothing to do with the running of the engine unless there is a fuel pump problem. It wouldn't even be there if it was not for safety when the diaphragm goes bad. If there is no fuel in it is it fine.

 

[Redwing4900]

My point was that I was wondering why there was anything in this line. Since I had something in there I could have changed the fuel pump, but I didn't, cleaned the line out so I could see something in this clear line in the future and also cleaned out the fuel pump, problem solved.

 

[airshot]

HMMMM......a 21 ft' Wellcraft with a 3.0 4 cylinder that does 30 mph at a little over 3000rpm just doesn't add up. You might want to check the ratio on your outdrive and see if it has been replaced with the wrong gear ratio. Not that that would cause a poor engine performance I do believe it is time for a complete tuneup and filter replacement but your speed and rpm don't add up for that heavy of a boat with a 4cyl motor.

 

[carrollcountybuckhunter]

HMMMM......a 21 ft' Wellcraft with a 3.0 4 cylinder that does 30 mph at a little over 3000rpm just doesn't add up. You might want to check the ratio on your outdrive and see if it has been replaced with the wrong gear ratio. Not that that would cause a poor engine performance I do believe it is time for a complete tuneup and filter replacement but your speed and rpm don't add up for that heavy of a boat with a 4cyl motor.

You are correct. I'm not sure why I stated 3.0 because it is actually a 5.0 (305). The air cleaner must of been off a 3.0 cause that's what's on the air cleaner but it's for sure a 5.0. You'll have to excuse me on that mistake, was a long day and I was all but asleep when I posted. LOL !

 

[carrollcountybuckhunter]

Is there a way I can edit the thread title to this ?

 

[carrollcountybuckhunter]

Ok so I took the boat to work with me this evening and a coworker that has several years experience in marine mechanics helped take the carb apart. It was a bit dirty but not as dirty as I was expecting. The spin on fuel filter wasn't that bad as well. We took 1 spark plug off to have a gander and it didn't look bad as well. The clear tube that runs from the fuel pump and up is clogged for sure and he mentione the choke looked to be way out of adjustment. We are gonna soak the carb and parts in some carb cleaner and rebuild it anyhow. Any more suggestions of what to look for ? Maybe timing and vacuum ?
There was a tag on the carb which I think is the serial number.

MCM 200
1389-9670

Found some numbers stamped on the carb as well.

13899670
7303

And the boat is a 1988.

 

[Eric 3.7LX Alpha 1]

There is a MCM 200 and it is a GM 305 but they stopped making the 200 in 1987.

In 1988 the GM 305 was called the 5.0L Not really a big deal but the engine would probably be an '85, '86 or '87..... depending on Serial #

see the chart

 

[Maclin]

Keep in mind that it is very common to have a prior year model drive train installed in the the "next" year's boat models as they work through old inventory.