farmerrick53
Contributing Member
Last year I obtained a 18' starcraft supersport with mercruiser and 140hp sterndrive. manifold and block were cracked and other problems. I had another 181 complete low hour motor with bad head. I built one out of 2 and she seems real solid. The manifolds were different in respect to carburetor bolt layout, one had older Rochester but was cracked, other had mercarb 2bbl but was clearly bigger carb. I am a fisherman so performance is not as important as reliability and economy. I found a sierra kit for the mercarb and went through it, set it to recommended specs, and float was too high, It would dribble on idle and miss and flood. I lower float and trolls fine now.
Now for the questions, when disassembled, this had a rubber stopper in the passage way from manifold to power piston. I removed and thoroughly cleaned everything. I reassemble. Now, at over 4000 rpm it goes way rich an misses. I lend jets down and I fixed it. If I leave small jet in It there is a slight lean condition, however if I disable the power piston and put original jets in, se runs like a dream, smoother, more economical, more power. Was there ever a 2 barrel mercarb available with no power piton or tunable power piston? Was it for smaller CID engines?
I run frequently at 8000' above sea level, blue mesa res. atmospheric density of 10,000 ft. on given days, took her to powell, and half the elevation, would almost handle factory jets and PV open, at 4200 rpm. However fuel consumption went up and lacked power. Has there been any experimentation to run no power valve and just main jets? I think these carburetors are a lot for these small cid engines, meaning vacuum deteriorates sooner/faster meaning power valve opens maybe long before it should since a larger cfm carb needs more air to maintain vacuum. Thanks for any good posts .
Now for the questions, when disassembled, this had a rubber stopper in the passage way from manifold to power piston. I removed and thoroughly cleaned everything. I reassemble. Now, at over 4000 rpm it goes way rich an misses. I lend jets down and I fixed it. If I leave small jet in It there is a slight lean condition, however if I disable the power piston and put original jets in, se runs like a dream, smoother, more economical, more power. Was there ever a 2 barrel mercarb available with no power piton or tunable power piston? Was it for smaller CID engines?
I run frequently at 8000' above sea level, blue mesa res. atmospheric density of 10,000 ft. on given days, took her to powell, and half the elevation, would almost handle factory jets and PV open, at 4200 rpm. However fuel consumption went up and lacked power. Has there been any experimentation to run no power valve and just main jets? I think these carburetors are a lot for these small cid engines, meaning vacuum deteriorates sooner/faster meaning power valve opens maybe long before it should since a larger cfm carb needs more air to maintain vacuum. Thanks for any good posts .
