4.3 mercruiser running lean.

[bluewater19]

I have a 2003 17 ft glastron 4.3 mercruiser 190 hp carb motor with a little over 2oo hrs on the stock plugs. I thought I would change out the plugs. After pulling and reading the plugs I found the following readings.<br />cylinder 1 and 2 were somewhat lean(white electrode with a little erosion), and the rest were fine (Light red in color with no erosion). The plugs are the stock AC double platnum.<br />I assume you read the plugs the same as you would on a car right?<br />Is this normal with this carb'd motor?<br />The motor runs great, I get good mileage, 4800 rpm WOT with a 23 pitch high five prop.<br />The boat starts right up every time. I just don't want to burn a valve or hole a piston<br />Thanks

 

[outboardguy]

Re: 4.3 mercruiser running lean.

Every motor that I've pulled plugs out of lately has the same description as yours,Lean. With the E.P.A.and C.A.R.B putting all the restictions on emissions at the factory level,Mercruiser has been setting them lean and plugging the idle mixture port.I would say it is probably normal and won't damage your engine.The major problem I've found with the lean run condition is that a lot of boats come in with a dieseling problem,if the mix was just a bit richer it would eliminate quite a few issues.

 

[trog100]

Re: 4.3 mercruiser running lean.

yes running lean can have its problems.. not saying u should do this.. i wouldnt dare.. he he.. but those plugs designed to stop factory settings being altered can be tapped out..<br /><br />i might be simple minded but to me.. if such things needed adjusting from time to time years ago.. they still do..<br /><br />trog100

 

[Richard Petersen]

Re: 4.3 mercruiser running lean.

Outboardguy. Does a advanced case of dieseling turn into Percolating of Fuel or Vapor Lock if bad enough after a power run? Thanks.