I have a 89 bayliner with a omc and a 302. I was thinking about switching from a two barrel carb to a 4 barrel (switching manafold also). Is there any difference between a marine carb and a regular car one? thanks
Basically no, But there are a lot of extra outlets, & vacuum lines usually on an auto carb that you have to figure out what to do with, and the choke, and throttle linkage may have a different configuration, that's not matching to the marine application, but maybe adaptable. By the way, is that a 302 Ford motor, or a 305 Chevy motor?
I had one of those it was a 188hp Mecruiser 302-2bbl in a 1974-18' Wellcraft Airslot. I believe it is the Windsor design, not the Cleveland design, and I couldn't find a 4bbl manifold for it at the time, unless I bought new, but I didn't have the money to spend.
Yes! there is major safety considerations that a marine carb has, but auto does not! Any carb in an I/O must be CG approved. While there is not allot of differences, it is critical to use a marine carb to prevent explosions within the confined space around an I/O. The main difference is fuel bowl venting. All venting must be directed down the barrels of the carb. If you look at a Holley marine vs auto carb, you will notice the prominent J tube vents on the marine version. There are also bushings, attachment place for fuel pump failure vent, accelerator pump seal, and other small changes to prevent/reduce chance of fuel dripping external. There are also non-safety differences, including the reduced vacuum line attachments, such as corrosion protection, and marine is jetted significantly richer than auto.
It is a real threat of explosion, and after the investigation all liability will be dropped in your lap - if you survived! Outside of that, you can get stiff fines from spot inspections on the lake. They probably will make you get towed, vs letting you drive back to ramp. Research through the I/O forum, every year there are numerous discussions on this.
Now back to your mod. I have seen a few posts of Ford 302 upgrading to 4brl. You will get some hp increase, but it isn't allot. You are probably talking only a 2-3mph wot improvement. If you are raw water cooled, and boat in salt or brackish water, finding a cast-iron manifold maybe somewhat difficult. If aluminum, you would need a marine specific (bronze water passages) and don't know of any being produced for the Ford 302.
Yea, at or near wot gas milage is going to drop. While there are claims that 4brls maybe more efficient when only running on primaries, it is always debatable and generally hard to prove. If you are worried about gas milage, having a good running carb is more important than changing.
Yes! there is major safety considerations that a marine carb has, but auto does not! Any carb in an I/O must be CG approved. While there is not allot of differences, it is critical to use a marine carb to prevent explosions within the confined space around an I/O. The main difference is fuel bowl venting. All venting must be directed down the barrels of the carb. If you look at a Holley marine vs auto carb, you will notice the prominent J tube vents on the marine version. There are also bushings, attachment place for fuel pump failure vent, accelerator pump seal, and other small changes to prevent/reduce chance of fuel dripping external. There are also non-safety differences, including the reduced vacuum line attachments, such as corrosion protection, and marine is jetted significantly richer than auto.
It is a real threat of explosion, and after the investigation all liability will be dropped in your lap - if you survived! Outside of that, you can get stiff fines from spot inspections on the lake. They probably will make you get towed, vs letting you drive back to ramp. Research through the I/O forum, every year there are numerous discussions on this.
Now back to your mod. I have seen a few posts of Ford 302 upgrading to 4brl. You will get some hp increase, but it isn't allot. You are probably talking only a 2-3mph wot improvement. If you are raw water cooled, and boat in salt or brackish water, finding a cast-iron manifold maybe somewhat difficult. If aluminum, you would need a marine specific (bronze water passages) and don't know of any being produced for the Ford 302.
Well I should have figured that, I know the fuel pump, distributor, alternator, and starter are marine specific for good reason's, no external spark, or gas vapors allowed, but you would think there would be some way to adapt the carb for marine use.
Yeah, I about gave up trying to find a stock 4bbl manifold, or an aftermarket (non aluminum) for my old 302/188hp Merc. That boat sounded so nice, someone had put long exhaust hoses angled to the outside corners of the transom, and brass outlets, just above the waterline on it. It was mellow, but ate gas by design,,,lol
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