DonS need expert advise on Mercarb

[pike hunter]

Mercruiser 5 liters serial # OD 709798<br />Carburetor: 2 barrels Mercarb<br />Problem: flooding<br />Explanation: I use my boat for salmon fishing on Lake Ontario. So trolling is the way to go. In the past I use to have a Mercruiser 4.3 LX with Rochester 4 barrels and never have any problem.<br />This year I trade my boat and now got a 5 liters with a 2 barrels. Rebuild the carb because flooding and still after a few hours of trolling it's start to run with a lot of smoke (black) and after maybe 5 hours of trolling the plugs are finish. Going back to shore, motor miss, backfire in the carb etc... Should I install a 4 barrels or is there a cure for my Mercarb?<br />Thanks for the answers<br />I need to fix that problem I almost lost 2 weeks of my holidays with that problem.

 

[achris]

Re: DonS need expert advise on Mercarb

Hi Pikehunter,<br /><br />I'm not Don, but I can offer some suggestions. <br /><br />The symptoms come on slowly, so the first thing I thought of is a float that is leaking, with a small hole in it. As the float fills up, the fuel level rises, causing the flooding. <br /><br />Some other things worth checking are fuel pump pressure. If the pressure is too high, then it could be pushing the float off its seat, causing flooding. Make sure the float chamber vent isn't blocked. When you rebuilt the carb, did you replace the needle and seat? <br /><br />As you open the carb up again you can check the needle and seat and the float.<br /><br />Good luck.<br /><br />[edit] Just thought to ask, the plugs, are they all black and sooty or oily?<br /><br />Chris.....................

 

[pike hunter]

Re: DonS need expert advise on Mercarb

Thankd for the advises. I check the float, I will have another look on the float chamber vent, needle and seat has been replace. The plugs are very, very black. I will also have a look on the pump pressure.<br />Thank's

 

[Don S]

Re: DonS need expert advise on Mercarb

Also make sure the float level is set to spec. Too high will cause flooding also.<br />Have you tried adjusting the fuel mixture using a vacuum gauge.<br />You might even want to do a comrpession test on the engine, since it seems to take a while before it starts causing problems.<br />Personally, I think prolonged trolling is awfully hard on a V8. Have you thought about putting a 4 stroke kicker on your boat for trolling?

 

[pike hunter]

Re: DonS need expert advise on Mercarb

Also make sure the float level is set to spec. Too high will cause flooding also.<br />Have you tried adjusting the fuel mixture using a vacuum gauge.<br />You might even want to do a comrpession test on the engine, since it seems to take a while before it starts causing problems.<br />Personally, I think prolonged trolling is awfully hard on a V8. Have you thought about putting a 4 stroke kicker on your boat for trolling? <br /> <br />

Float has been set to spec<br />Fuel mixture has been set by "ears"<br />Yes I plan to install a 4 stroke but not this year and I think I should be able to trolle with my V8. Many guides around are doing so<br />Should I replace the Mercarb with a Rochester 2 barrels if I don't go for a 4 barrels. <br />What are the jets size available for the Mercarb?