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  1. #1
    Cadet
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    Default Rochester 2bbl carb

    Replaced my 1982 2.5L Mercruiser with a new 3.0L long block and now I think it is time to tackle the carburetor. I'm positive the carb is shot - mixture screws do nothing and i'm getting gas residue around the throttle.

    The carb number is 17059054.

    My question - i've found a few remanufactured carbs (i.e. Sierra 18-7609) on the internet - are these any good? I'd prefer to replace the carb rather than try to rebuild (summer is quickly passing me by) but I want to make sure that a re-manufactured is the way to go. Are these completely rebuilt to factory specs? Anything I should watch out for? Should I look at other brands and if so - where?

    I'd appreciate any comments or suggestions.

    Thanks !

  2. #2
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    Default Re: Rochester 2bbl carb

    Your carb is about as easy a rebuild as you will find and the kit is way less $$ than a remanufactured carb. Worst case is you will have to get a new/reman carb later if it does not work well. Should only take 24 hours if you let it soak in carb cleaner all night. NOTE: This model carb is notorious for a sticking choke resulting from a distorted throat caused by repeated tightening of the air filter/flame arrestor hold-down nut. I always have been able to save them by filing the edges of the choke plate to fit the throat. Good luck!
    Last edited by Willyclay; July 21st, 2008 at 11:21 PM. Reason: Spelling

  3. #3
    Petty Officer 1st Class bigbob_FTW's Avatar
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    Default Re: Rochester 2bbl carb

    I second that. Just rebuilt mine and its a breeze. works great now.
    1984 Cobia Charger, 120 Mercruiser/Alpha 1

  4. #4
    Moderator Bondo's Avatar
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    Default Re: Rochester 2bbl carb

    Are these completely rebuilt to factory specs? Anything I should watch out for?
    Ayuh,.... Just make sure you buy the Right 1....
    Any Grease is Better,..... Than No Grease at All.......

  5. #5

    Default Re: Rochester 2bbl carb

    I have an 87 Mercruiser 175. THe tag on the carb is MCM175/3304-9565.
    I rebuilt it, but afer runnning for a little bit, I get gas leaking from the bottom. At this point I really just want to replace it.

    I talked to ******************** and they don't have my numbers. THey say mine are for a Mercruiser Carb and they only do Rochesters. Can anyone tell me which Rochester will fir. From loking at the pic on their site, I don't see any difference. (fittigs, location of elec choke, fuel inlet, etc)

    Thank You in advance.

  6. #6
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    Default Re: Rochester 2bbl carb

    Another question on rebuilding: My manual mentions checking the throttle shaft to determine if it is worn or loose - and if so to replace the entire throttle body. A mechanic actually warned me not to rebuild for this very reason. He said there may be shafts, bushings, etc that need to be replaced that aren't part of a kit. Does this make sense and how available are these "extra" parts?

    Thanks.

  7. #7
    Petty Officer 1st Class bigbob_FTW's Avatar
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    Default Re: Rochester 2bbl carb

    I guess if you want to be real anal about it (not meant to be a nock). You really can't loose by trying. If it doesn't work, you aren't out much. I've done mine several times, and it runs great.
    1984 Cobia Charger, 120 Mercruiser/Alpha 1

  8. #8
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    Default Re: Rochester 2bbl carb

    On the other hand, going the reman carb route isn't without its problems! Bond-0 already flagged the challenge of getting the correct carb. Even if you get the correct one, it may have issues like missing or improper parts that will require another removal and replacement, not to mention the hassle factor. I'll wager you could go to a large auto salvage yard and get a bucket of Rochester 2-barrels for a few bucks so you could mix and match parts until you like the end result. But I'm an old guy and think like that!

  9. #9
    Petty Officer 1st Class wewefirex2x's Avatar
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    Default Re: Rochester 2bbl carb

    I ordered a reman carb off the internet. My boat had the Mercarb on it so that is was I purchased. When UPS came I opened the box and recieved a Rochester 2 Barrel. I called and they tsaid it was the same carb. After about fifteen minutes of telling him it's not the same I just decided to keep it. Everything on the carb is the same as the Mercarb, but you get two mixture screws. I only wanted what I paid for, if I wanted a Roch I would have ordered a Roch.

  10. #10

    Default Re: Rochester 2bbl carb

    Do you have the numbers on the Rochester? WHo did you get it from>? Thanks,
    I am finding them from $217 up to $605!!!

  11. #11
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    Default Re: Rochester 2bbl carb

    OK - It seemed like the majority opinion was that I should rebuild - so the carb is in pieces on my workbench and will soon be soaking.

    I've been looking around for a rebuilt kit and Autozone told me that the kit for my carb (17029054) was GP Sorensen 96-670. I remember my repair manual warning against using automotive gaskets because they can weep gas, but since this kit seems to be for my exact carb should I assume that it is OK for a marine application?

    As far as I could tell, the OEM kit is 823427A1.

    Thanks,

  12. #12
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    Default Re: Rochester 2bbl carb

    That may be more of a problem on a Holley carb because of their design. I can't see it being a problem on your carb. By the way I just rebuilt a Merc (almost the same as your Rochester) using a marine kit and the gaskets didn't look any different than the ones I used to put in cars years ago.

  13. #13
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    Default Re: Rochester 2bbl carb

    Soak that sucker overnight in some acetone. Make sure you blow it dry with compressed air. Make sure every little hole is CLEAN. Hold it up to the sunlight.

    Every hole is clean. I know i wrote it twice. Replace the ball bearing. And make sure the accelarator pump fits tight.

    Been doing this a long time first one i was 13, 1959 triumph.

  14. #14
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    Default Re: Rochester 2bbl carb

    Us old guys like to use Permatex (non-hardening) on gasket surfaces to insure we only have to do the job once. Good luck!

  15. #15
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    Default Re: Rochester 2bbl carb

    Good idea the permatex just a drop. Keep the gaskets from moving.

    However he might have to take it apart again being it's his first time.

    Maybe the float isn't right, maybe all the holes not clean.

    May i suggest sir; you run it from a external tank with CLEAN FRESH GAS.

  16. #16
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    Default Re: Rochester 2bbl carb

    Here is a story for you. I decided to rebuild my Roach but found that it had a jammed check ball. Fragged. I'm a big car guy and got to thinking about what has been mentioned above, Junk yads are full of rochesters. I went and grabbed a few for,..free..but found some differences in venturi diameter etc etc. Also as you know, car carbs vent to the atmosphere,..not good in a boat. Decided I make good money and my family didn't deserve one of my frankenstein ideas and bought a reman. Guess F'ing what I got??? A converted car carb painted Merc black. Simply what I was going to do to the T! Live and learn.

  17. #17
    Honorary Moderator Emeritus Don S's Avatar
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    Default Re: Rochester 2bbl carb

    I wouldn't allow any of you "Carb Rebuild Experts" even near a carb of mine. This thread is so full of mis-information it's scarry.
    Don S.


    Please, no PM's (Private Messages) regarding boat/engine problems.
    That is what the forums are for.
    Only forum/moderator issues will be answered in PM's.

  18. #18

    Default Re: Rochester 2bbl carb

    So can anyone tell me the Rochester model # to use on an 87 4.3 with THunderbolt IV ignition? Thank you

  19. #19
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    Default Done - sort of

    Soked it, cleaned it thoroughly and everything went back together ok.

    Installed it this evening and the engine ran rough, and then I noticed gas percolating out of the top of the carb.

    I had used the old float and measured per the instructions - and the float lined up exactly where it should have been i.e. it was set right when I took it out. The only variable I could think of was the washer on the needle seat. There were two in the kit and I had used the thin one. So, I pulled the carb and swapped out the thick washer and re-assembled.

    That stopped the gushing gas, and the engine runs great at idle, but anything above idle runs very rough. I also noticed that as I advance the throttle, the engine rpm will jump around like it is having trouble in the transition.

    Could this still be a float issue or does it sound like something else?

    Thanks,

  20. #20

    Default Re: Done - sort of

    You should use the same needle seat washer from the kit that was already in your carb. If it had the thick one, use the thick one - vise versa. I just did a carb job on mine last weekend and the needle valve was stuck open (float was stuck down) when the bowl initially filled with fuel after I re-installed it. Float height & drop was set to spec. A couple of taps on the side of the carb brought the float up where it should be and it ran great after that. (I used to fill the bowls with fuel during re-assembly when I worked on air-cooled VW carbs, and that would have prevented the above from happening)

    Did you disassemble the entire carb per the mercruiser service manual and set to spec? Soak what should be soaked and then blow out every passage? Have you verified the ignition system is per spec?

  21. #21
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    Default Fixed - sort of

    Tore the carb back down and reset the float - that seems to have fixed the running rough problem. However, the engine still has trouble around 2000 rpm.

    The engine starts almost instantly, runs great at idle, and runs great at 2500-3000 rpm. However, the transistion from idle to full speed is rough. If I try to set the throttle to 2000 rpm, the engine either bogs down and the RPM's drop - or it surges up to 3000.

    I'm assuming that there is something wrong with the mid circuit in the carb. The engine acually did this before I rebuilt the carb so maybe there is something wrong in the carb that I missed or that the rebuild kit didn't cover. Any suggestions on what to look at next?

    I will say the engine starts a 1000 times better after the rebuild. Just breathe on the ignition and the engine fires right up, even after it's been sitting over night.

    I appreciate all of the suggestions and the re-build wasn't nearly as difficult as I anticipated.

  22. #22
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    Default Re: Rochester 2bbl carb

    Since Don S has not jumped in to help you, looks like you are stuck with us "non-experts"! Did your rebuild kit come with a new Main Jet? If not, did you visually verify the old jet was clear by blowing compressed air through it after soaking and/or passing something like weedwacker line through it?

    Additionally, since you now say the problem is occuring during throttle transition, did your rebuild kit come with a new Power Valve and Power Valve Plunger? If not, this may be a problem area to work on.

    Also, as another poster already suggested, your ignition needs to be right. I had the personal experience of spending a long day in the ICW because of a weak/bad coil on an inboard engine. It started and idled great, but fell flat and ran real bad at anything above 1,500 RPM.

    Finally, any chance you have bad gas? Can you put fresh gas in a remote/outboard tank and try that just to be sure?

    We'll keep trying as long as you are willing! Good luck.
    Last edited by Willyclay; September 9th, 2009 at 01:56 PM. Reason: Grammer

  23. #23
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    Default Re: Rochester 2bbl carb

    Glad to hear you are making good progress. I was typing as you were posting so some of my latest post does not apply. Thanks for keeping us updated.

  24. #24
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    Question Re: Rochester 2bbl carb

    can anyone tell me why i have to clamp the rubber line coming from the fuel pump to the back of the carb in order for it to run?

  25. #25
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    Default Re: Rochester 2bbl carb

    Quote Originally Posted by boaty89 View Post
    can anyone tell me why i have to clamp the rubber line coming from the fuel pump to the back of the carb in order for it to run?
    Incase the fuel pump goes bad the gas will go into the carb. Its a vent for the fuel pump.

    Don S, Im confused why you say the info is scary but you didnt say why or help anyone?
    1990 Stardust
    -Dual Chevy 305's with Volvo DP's

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