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wufwee
07-21-2010, 09:03 PM
I've got a 1990 16 w/ a 4.3 OMC. The previous owner had someone try to get more speed by changing the jets in the secondaries. I'm not sure what else was done. The engine flutters when going from 3/4 to 7/8 throttle, and smoothes out when wot. It eats fuel like there's no tomorrow. I've contacted some Carb. rebuilders, but something tells me no matter how much I tell them about the secondary jets, I'll still get a run of the mill rebuild kit installed and still have this problem because the jets won't get changed to a stock size for my altitude. For all I know, the spring in the diaghram has been changed. What I really want is a replacement carburetor and so far no one has one on the shelf. Jeggs has a brand new one on the shelf for $411.00, and at this point in the season, I'm tempted to get one. Any advice? Thanks, Russ

BUIZILLA
07-21-2010, 09:21 PM
what carb?

wufwee
07-21-2010, 10:09 PM
Ooops, it's a Holley four barrell 600cfm 4160.

jonzis donzi
07-22-2010, 07:20 AM
I've got a 1990 16 with a 4.3 also. Mine has a Rochester Quadrajet on it. Some people probably think they're junk, but it works great and is really easy on gas. It runs mainly on the primaries, front two barrels, and the secondaries are vacuum operated and only open as far as needed under full throttle so gas isn't dumped through and wasted. It's a miser, but still performs well when railing on it. Just my 2 cents worth!

Cuda
07-22-2010, 09:16 AM
I've got a 1990 16 with a 4.3 also. Mine has a Rochester Quadrajet on it. Some people probably think they're junk, but it works great and is really easy on gas. It runs mainly on the primaries, front two barrels, and the secondaries are vacuum operated and only open as far as needed under full throttle so gas isn't dumped through and wasted. It's a miser, but still performs well when railing on it. Just my 2 cents worth!
The primaries are small with huge secondaries. They are adjuted with metering rods. I believe they were all 750 cfm.

If you have a Holley, you can but a kit with a bunch of different sized jets. They are easy to change. Try different sizes until you find one that works. It was less than $20 for the jets. I wouldn't buy a new carb. There isn't that many things that can go wrong with a carb. I could rebuild a Holley with my eyes shut. The Q jets are much more complicated.

Phil S
07-22-2010, 10:12 AM
It kind of sounds like the secondaries are opening too soon. If they open too soon your engine will bog down from too much fuel. That could be the "fluttering" you mentioned. You can buy a Holley secondary spring kit that will come with about 7or 8 springs of differing strengths. It's fairly easy to change the spring, even easier if you buy Holley's quick-change kit. Both parts are usually less than $20 bucks a piece.

I've read on here that a lot of folks aren't fans of vacuum secondaries on a marine application, and I understand why now after having to go through several spring changes on mine to get them to open up at the right time.

Hope this helps.

Phil S.