Mercruiser inline 6 carb questions??

[1968 sterncraft]

I have a 1968 Mercruiser 165 hp inline 6 with a 2bbl carb. (same as a 250 chevy) I have rebuilt this carb twice and I am still having bad luck with it. ( I have rebuilt many carbs for older Chevy trucks that ran perfect) So my question is for the type of engine I have is there a 2 bbl Holley carb that will work on my engine? If so does anyone know where I can find one?

My boat is almost impossible to start when it sets for any amount of time over a week. When it does start it will not open up to full throttle. Sometimes after running for about 45 minutes or so if I shut it off it has to cool down before it starts again. Just too many problems to list. I have checked the fuel lines, vents, filters, water separator, and so on. Everything seems to be in check. I was considering switching to a Holley carb because on old trucks with the chevy 250 I always liked the Holley carbs and not the rochestor carbs. I have searched for a few days on the internet but all I can find are the Holley carbs for Ford applications or if it is a Chevy it's for a larger engine. Any help or comments or suggestions will be gladly appreciated. Thanks.

 

[achris]

Re: Mercruiser inline 6 carb questions??

Have a look at HERE....

I think this is what you're looking for....
They do a 300cfm as well, but I think that'll be too small for the 250cid
Please make sure you use a MARINE rated carb, not automotive...


Chris........

 

[ziggy]

Re: Mercruiser inline 6 carb questions??

bummer the rebuilds havn't worked out for you. the 2gc is a good carb best i can tell so something could be up. myself, i would not look to replace the 2gc with something other than another 2gc. the 2gc carbs seem to work very well with the chevy 250.

some carbs are just not rebuildable for some reason, maybe you have one of them. R&R with a different 2gc.

did you use the mercruiser s/m for specs to set your 2gc up to and did you confirm that all specs have been met.

i assume since you've rebuilt carbs before, you soaked the carb clean and used compressed air to blow through all small passages.

theres a trouble shooting guide in the s/m for carbs. have you looked at that?

sounds like you've looked at the fuel side, perhaps the fuel sticky will offer further insight.. http://forums.iboats.com/showthread.php?t=283269

have ya done a compression test to be sure you have something to work with? have ya done a minor tune up recently to illimnate the electic side for possible problems prior to working on the carb?

again, i'd stick with the 2gc. when everything is right they work very well.

 

[dan t.]

Re: Mercruiser inline 6 carb questions??

any holley will require a adaptor plate to fit,most of these are poorly designed and will not do anything for the air flow. personly I would stick with the rochester but each to his own, the 300 cfm will be plenty of cfm for a 250 cid motor

 

[kilowatts]

Re: Mercruiser inline 6 carb questions??

Hi Guys:
I agree with Ziggy. There's not much point in changing the Rochester carb on a 250 inline 6 as there will be little to no difference in performance other than the high cost of a new carb and increased gas milage. Over the last 18 months I've rebuilt 3 inline 6's. With one, I bought a new rebuilt marine Rochester 2GC with a 6 month guarantee and a pamphlet guaranteeing the marine settings, all for around $CAD125.00. With another I sent the carb out for rebuild with the spec Mercruiser settings for around $CAD250.00 plus shipping from Vancouver, BC to Montreal, QC and back. With the last one I rebuilt it myself for the cost of an OEM rebuild kit and cleaning materials around $CAD100.00. All three perform equally as well and if I had to do it again I have no doubt that I would buy a new rebuilt carb with a guarantee. Cheaper and better quality!
The other thing is, there's less chance of a problem out on the water if I buy from pros rather than take a chance on a self rebuild. As you can guess I'm not a pro!
Good luck:
kilowatts