Mercruiser carb

[popey]

hi there

My engine is a Mercruiser 165 IL6 with a 2brl carb. I have heard of 4brl ones as well. What is the difference, advantage?

Best Regards,

popey

 

[ChrisCraftJohnny]

Re: Mercruiser carb

The 4BBl carb would be for a larger application. Such as a 305 V8 and up. Some run a 4BBL on the 4.3L V6 vortec. But the CFM a 4BBL needs is more in tune with V8 engines.

The 2BBL you have on your Merc. is perfect for the application. The Mercarb 2BBL is very easy to rebuild. Make sure you use a Merc Quicksilver kit not an aftermarket kit.

If you were to place a 4BBL carb on your engine, you would get massive bogging and very poor over all perfromance. In fact, my old FORD 300 CID inline 6 had a 1BBL Carter Carb that ran the engine perfectly!

CCJ

 

[GLENN M]

Re: Mercruiser carb

the 165 hp 4 cyl 3.7l had 2bbl and rated higher with 4bbl,but i dont think 165 6cyl ever came with 4bbl,if you could find a manifold try it

 

[ziggy]

Re: Mercruiser carb

best i know....

the 165hp L6 (chevy 250 cid) always came with a rochester 2gc. 2bbl.
it's a good carb for the application and there's no need to mess with it. anything else will disappoint i believe..

there is (was) a 200hp L6 (chevy 292cid). it was only used in '68 and '69 and was mated to a mercruiser II drive. it i believe had a 4bbl on it. for whatever reason. that system only lasted them 2 years. i assume it was somehow unsuccessful as a marine application for some reason.

anyways. there's nothing (never say never, i know, but generally speaking) ya can do to make your 165hp L6 anything other than what it is. tune yers up good, use good parts and have a great engine for your boat. one of the best engines ever used for marine application, imho.

 

[kilowatts]

Re: Mercruiser carb

Hi Guys:

I agree with Ziggy. I think you can change to a 4bbl carb with a new manifold adapter but I don't believe you'd get any better performance in any way except that you'd likely use more gas and foul the plugs. If you have an inline 6 then you already have one of the best engines for marine use, it just won't let you change it into something else! It is what it is!

kilowatts

 

[cr2k]

Re: Mercruiser carb

Mercarb has ONE idle adjust needle
Rochester 2GC has 2.

There are 2 variations of the Mercarb, so you need to take the tag number in to get the right kit.

 

[86 century]

Re: Mercruiser carb

The plate under you 2bbl is the same as square bore 4bbl. You can get your 4bbl on there fairly easy and may get slightly better fuel economy at lower throttle settings due to the smaller ventury but I would not expect to notice any thing any where else.
Good Luck

 

[zbnutcase]

Re: Mercruiser carb

If your gonna change carbs at all, I would stick to 2bbl and use the 500cfm Holley marine carb....

 

[Harte3]

Re: Mercruiser carb

What zbnutcase said. Having said that, I am a fan of the 240/300 Ford I6. I have the 300 in my 1983 F150 and it is mildly modified with a 4v holley 465 cfm,Comp 260h cam and modified DS2 ignition. Pulls loads much better than the stock engine did and gets better mpg and I have often wondered how it would work in my 19' BlueWater that has a 4.3. But, I'm not going to spend the resources to find out.

If one were to go the 4v route on an inline marine 6 I would consider a Qjet...small primary bores for low speed and moderate cruise and the "toilet flusher" secondaries for the feed "Exxon" moments. With proper adjustment, the bog can be eliminated.