Replace Mercarb by a Rochester?

[pike hunter]

Mercruiser 5L, 1992, mercarb carb. Do you think I can get better overall performance with a Rochester 2 barrels with the 2 idle mixture screws vs the mercarb with the one mixture idle screw.<br />Having only problems with that mercarb. It has been rebuild,everything else has been double check and still not working ideally to get my full confidence.<br />Main problem left, is after a run and sitting for lets say 10-15 minutes, very hard to start; never sure if it would start again. The other day I had to use the kicker to return dock (12 miles run) <br />Wife has a good one: this boat is allergic to water

 

[lilmandavis]

Re: Replace Mercarb by a Rochester?

is it overheating? does it just die like theres no fuel? does it crank over easily? are you sure its the carb?

 

[Mile-High Mariner]

Re: Replace Mercarb by a Rochester?

Sounds like a vapor lock issue. Mercruiser actually issued a Service Bulletin related to methods of cooling the fuel line in certain applications - you might want to query the Search app for "vapor lock" and see what you find. The MerCarb is actually a great carburetor, but it's, well, a CARBURETOR! If I'm not mistaken, MerCarbs are actually just Mercury Marine's rendition of a Rochester carburetor, produced by MCM after Rochester discontinued production of their marine carburetor line.

 

[Laddies]

Re: Replace Mercarb by a Rochester?

Actually the Merc Carb is Mercury Marine cheap version of a carb that worked very well for many years, that is trouble some, the first couple of years prodution had many update kits for dealer to try to get them to work properly, the newer ones are better but trouble some but that don't sound like your problem I don't quite understand if the engine is not cranking or not starting.

 

[DJ]

Re: Replace Mercarb by a Rochester?

There are aftermarket carbs out there. If you change, MAKE SURE you use a marine rated carb. There is a big difference regarding safety and fuel spillage issues.<br /><br />However, no carb can overcome a weak fuel pump or vapor lock issue.

 

[pike hunter]

Re: Replace Mercarb by a Rochester?

lilmandavis: no overheating,does crank over easily,after checking everything I think it's the carb (maybe a bad casting?)<br />Laddies: engine is cranking but don't start or barely start after playing with trottle.<br />DJ: Yes I will buy a marine carb.<br />I may be wrong with that change but can't see what else can be wrong.

 

[Laddies]

Re: Replace Mercarb by a Rochester?

Pike hunter run the engine till it acts up, then remove the flame arrestor and ck to see if the choke is not opening, if it is and the carb is flooding toy should see excess fuel running down the throat of the carb, if not have someone pump the throttle to see if there is fuel in the carb, if it don't squirt fuel then take a squirt can and squirt fuel down the throat replace the flame arrestor in see if it will start. THe wyou will have a idea if it flooding,vapor locked or if the problem is fuel or spark