Hi all...
I'm battling some really poor performance and fuel economy issues. I'm still going through the usual list (props, bottom growth, weight, recheck timing, do a vacuum test, etc....already did a full tuneup) but I hoping for some advice on 2bbl Mercarbs vs 2 bbl Rochesters (twin 1999 5.0L, Bravo 2 in a Bayliner 3055).
When I got the boat it was in rough shape and the carbs hadn't been serviced as far as I could tell (nor much else!). At the first sign of idle and performance trouble last year I took another boater's advice (verified by several boaters on the 'net) and replaced the original Mercarbs with equivalent Rochesters from I5 instead of rebuilding the Mercarbs.
Since then I found a bigger culprit on the performance issues, but after fixing that one motor still isn't reaching WOT (500-600 short), the other motor is a little short (100-200 but that could be simply because the other one is creating drag?), and the fuel economy is TERRIBLE (roughly .5 mpg or worse at cruise rpm according to the FloScan).
I'm thinking of rebuilding the Mercarbs and putting them back on. Any feedback on this? Are the Mercarbs and Rochesters supposed to be the same CFM? Any reason to think the Mercarbs would be more efficient? Less? Any other advice on possible causes of the problem?
On a related note, if anyone is an expert on Rochester two barrels....I noticed that one of the carbs has three tiny holes along the rear edge of the 'deck' around the top of the barrels i.e. if you're looking down into the carb, there is a ledge around the top of the barrels that then curves down to form the barrels themselves. The other carb does not have these holes. Coincidentally, this motor is getting the worst fuel economy and that won't reach WOT spec.
Any help/ideas are much appreciated.
Edit: Maybe this is more about I5 than it is about Rochester carbs. I'm starting to see some posts from people who tried them and had problems with running too rich, etc. My problems could easily be due to running too rich. Does anyone have an opinion or experience with I5 rebuilt carbs, specifically their Rochester 2bbl replacement for Mercarb?
K
I'm battling some really poor performance and fuel economy issues. I'm still going through the usual list (props, bottom growth, weight, recheck timing, do a vacuum test, etc....already did a full tuneup) but I hoping for some advice on 2bbl Mercarbs vs 2 bbl Rochesters (twin 1999 5.0L, Bravo 2 in a Bayliner 3055).
When I got the boat it was in rough shape and the carbs hadn't been serviced as far as I could tell (nor much else!). At the first sign of idle and performance trouble last year I took another boater's advice (verified by several boaters on the 'net) and replaced the original Mercarbs with equivalent Rochesters from I5 instead of rebuilding the Mercarbs.
Since then I found a bigger culprit on the performance issues, but after fixing that one motor still isn't reaching WOT (500-600 short), the other motor is a little short (100-200 but that could be simply because the other one is creating drag?), and the fuel economy is TERRIBLE (roughly .5 mpg or worse at cruise rpm according to the FloScan).
I'm thinking of rebuilding the Mercarbs and putting them back on. Any feedback on this? Are the Mercarbs and Rochesters supposed to be the same CFM? Any reason to think the Mercarbs would be more efficient? Less? Any other advice on possible causes of the problem?
On a related note, if anyone is an expert on Rochester two barrels....I noticed that one of the carbs has three tiny holes along the rear edge of the 'deck' around the top of the barrels i.e. if you're looking down into the carb, there is a ledge around the top of the barrels that then curves down to form the barrels themselves. The other carb does not have these holes. Coincidentally, this motor is getting the worst fuel economy and that won't reach WOT spec.
Any help/ideas are much appreciated.
Edit: Maybe this is more about I5 than it is about Rochester carbs. I'm starting to see some posts from people who tried them and had problems with running too rich, etc. My problems could easily be due to running too rich. Does anyone have an opinion or experience with I5 rebuilt carbs, specifically their Rochester 2bbl replacement for Mercarb?
K
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