Bought a 1999 Larson 186 lxi 3 weeks ago w/ 1998 4.3GS PBYC engine and SX outdrive.
A LITTLE HISTORY: Guy I bought it from said the engine was missing last time on the water. He was the 2nd owner and had it only one season. He thought it was a bad carb. Not being a mechanic himself he took it to one who installed a brand new Quadrajet 4 bbl 4.3l-OMC carb. I have the receipt. It was put on June of this year. Guy says mechanic told him that after he took old carb off that he didn't think that he was having carb issues afterall - that he thought it was probably bad gas. Guy still paid for the new carb to be installed, filled up the boat with new gas on top of the old gas, went to the lake and it was still missing badly. He changed jobs and didn't have time to deal with it. I get a good deal on the boat so I buy it. Before even putting it on the water I rebuilt and re-upholstered the engine compartment cover which was falling in. Then drained all the gas from the tank. Had a friend who worked as a marine mechanic for 6 years come over and do a check up on the boat. Checked compression on it and one cylinder was dead and one was weak. Pull the head and had two tuliped intake valves. Had the head fixed and reinstalled a few days later.
THE ISSUE: After reading countless threads/posts on this forum about the possible causes for tuliped valves the general consensus seems to be that its most likely "RUNNING TOO LEAN", followed by "OVER PROPPING". Being the 3rd owner of this boat I have no clue as to how the boat was tuned previously or if it was over propped. The Volvo Penta Manual states that this engine came with a HOLLEY carb, NOT a Quadrajet. So, we are trying to start from scratch with the new head and tune the Quadrajet the way it should be WITHOUT being too lean in order to avoid tuliped valves again (if that was the cause).
WHERE WE ARE TODAY: Engine fires up and runs fine on the muffs. BUT we are having a hell of a time finding specs on this Quadrajet carb (MODEL: "QJE 4.3L-OMC"). Buddy called the former marine place that he worked trying to get specs and they had no info on it. Called autozone where it was purchased and no luck there either. My buddy keeps mentioning the "CFM" for this carb model. Obviously we just need to know how to properly tune this thing. Any guidance on this matter from you fine gentlemen would be more than appreciated. My buddy has got it running smooth at idle on the muffs but without any carb specific specs we feel like we're shooting in the dark. It may not matter but is there possibly any info I can get from the carb itself, like a serial # or something, that can help me locate data that would help us out? Thanks again
This is the carb (only this exact one is for a 5.0, not 4.3):
A LITTLE HISTORY: Guy I bought it from said the engine was missing last time on the water. He was the 2nd owner and had it only one season. He thought it was a bad carb. Not being a mechanic himself he took it to one who installed a brand new Quadrajet 4 bbl 4.3l-OMC carb. I have the receipt. It was put on June of this year. Guy says mechanic told him that after he took old carb off that he didn't think that he was having carb issues afterall - that he thought it was probably bad gas. Guy still paid for the new carb to be installed, filled up the boat with new gas on top of the old gas, went to the lake and it was still missing badly. He changed jobs and didn't have time to deal with it. I get a good deal on the boat so I buy it. Before even putting it on the water I rebuilt and re-upholstered the engine compartment cover which was falling in. Then drained all the gas from the tank. Had a friend who worked as a marine mechanic for 6 years come over and do a check up on the boat. Checked compression on it and one cylinder was dead and one was weak. Pull the head and had two tuliped intake valves. Had the head fixed and reinstalled a few days later.
THE ISSUE: After reading countless threads/posts on this forum about the possible causes for tuliped valves the general consensus seems to be that its most likely "RUNNING TOO LEAN", followed by "OVER PROPPING". Being the 3rd owner of this boat I have no clue as to how the boat was tuned previously or if it was over propped. The Volvo Penta Manual states that this engine came with a HOLLEY carb, NOT a Quadrajet. So, we are trying to start from scratch with the new head and tune the Quadrajet the way it should be WITHOUT being too lean in order to avoid tuliped valves again (if that was the cause).
WHERE WE ARE TODAY: Engine fires up and runs fine on the muffs. BUT we are having a hell of a time finding specs on this Quadrajet carb (MODEL: "QJE 4.3L-OMC"). Buddy called the former marine place that he worked trying to get specs and they had no info on it. Called autozone where it was purchased and no luck there either. My buddy keeps mentioning the "CFM" for this carb model. Obviously we just need to know how to properly tune this thing. Any guidance on this matter from you fine gentlemen would be more than appreciated. My buddy has got it running smooth at idle on the muffs but without any carb specific specs we feel like we're shooting in the dark. It may not matter but is there possibly any info I can get from the carb itself, like a serial # or something, that can help me locate data that would help us out? Thanks again
This is the carb (only this exact one is for a 5.0, not 4.3):
