tmthunder

I have a 1990 Carb'ed 502MAG in my boat. I am looking to rebuild the stock Q-Jet. What is the part number for the marine rebuild kit and float from Napa or other parts stores? Also any input on modifications that you have made to similar carbs would be nice. I have Dennis's book and the Q-Jet book by Doug Roe but that one does not mention marine applications. Thanks for your help.
Brian

Biggus

iTrader: (1)

tmthunder,

Just sent it to Hobbs Carburetor in Pelham , NH.

Hobbs specializes in Quadrajets and has same day turaround. I`ve done business with them for years. Just bolt it on and it`s perfect everytime.

blue thunder

I don't know the napa part number, but they are not all that expensive in the marine version. I bought mine from BAM. Be careful when buying a rebuild kit because some of them come with a needle and seat smaller than merc used stock, .125 I think it was. When I rebuilt mine I used a .149 neeldle/seat (and lowered float level), went up one size on the metering rods (actually smaller rods), bought an assortment of rod hangers and went up in jets on the primary side. I didn't do anything with the power valve spring. During tuning I played a lot with the air valve setting but pretty much ended up adjusting it to the factory recommended 1/2 turn. I bought a book on tuning qjets for performance which had a lot of other tricks but I basically stuck with changing parts instead of drill things out. Can't find the book now to save my ars. Bought all the parts from summitracing.com

Dave

Liberator21

Some guy on Ebay is selling OEM Mercruiser rebuild kits for about $29.00 or something like that. Email him to see if it fits your carb. That price is pretty good. I just bought mine at a local auto parts store. I paid $24.00 for a Borg Warner kit, but I did order the big needle and seat from Carbs Unlimited. Got new jets and rods too. They wanted $48.00 for their rebuild kit. OUCH!!! Be careful with the mods, especially what you find online. Some bozos say just drill everything out! Once it's drilled, you can't go back. Were you having any problems with it? Or do you just want to freshen it up?
Hey Blue Thunder, How did the carb work after the rebuild? I bought a rebuilt carb, and put it on my new engine. The boat pulls like crazy up to 4600 rpm, then hits a wall! My old carb on my old engine never did that. I didn't send my old carb back for the core charge (good thing), so now I'm in the process of rebuilding that. I'm also toying with the idea of powder coating the body. That would look good, but it's a lot of extra work.

blue thunder

The carbs ran real strong liberator but I thought I should be doing better. I bought a couple 800 holley double pumpers and am rebuilding them now. Hopefully I will get an improvement at WOT and throttle response, but if not, at least they are pretty mercury racing blue

Dave

Liberator21

I hope mine runs well. I just ran out, and picked up a book on modifying Q-Jets and Holleys. Looks like my carb was pretty set up allready (According to this book).
Now the question is, what color should I powder coat it?
The engine is purple.

tmthunder

Thanks for the info. This last season my top end seemed to be about 500 RPM's short of the previous year so I think it is time to freshen up the carb. Biggus do you have a number for Hobbs? Thanks again and maybe I will get my boat down to the Sebago area this year I normally run in the Millinocket area.

Liberator21

tmthunder, did you take your carb apart yet?

tmthunder

Liberator21,
I have not taken it off yet because it has been so cold here.