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View Full Version : '79 / 1975-1977 2 barrel carb problems on 233hp 351


Sidewinder
08-12-2009, 01:11 PM
Hello, I have a few carb questions concerning 1979 MC Skier. It is fitted with a 1977 233hp 351 Mercuiser (srl # 4621712) with a two barrel carburetor (srl # 1376-6152A1 and model # MCM-MIE-233). Not sure if the engine is original or not, but from what Iíve read in previous posts MC apparently used whatever engines they could obtain during the late Ď70ís due to demand. Also not sure if it is a Rochester or Mercruiser Carb. I've attached a few pics hoping someone can identify it.

Anyway, the carb had a carb-kit installed prior to me purchasing the boat this spring. When the kit was installed it ran too rich and the previous owner had a mechanic friend adjust the float iot lean it out. I bought the boat after that and I successfully ran 4-5 tanks of fuel through it since then and it ran fine. Two week-ends ago a friend was driving and he went from 4000+ rpms to neutral in a very short distance and the boat subsequently stalled out Ė donít worry he was spoken to about this! ;) Anyway, the boat wouldnít restart b/c the carb was flooded out Ė so much so that it was leaking gas onto the manifold.

After drying the gas off of the manifold and waiting approx 30 minutes it started up, but had a tremendous amount of black smoke coming out the back and sounded like it was missing. Iím assuming it was obviously running way too rich. A fellow boat came along and suggested that I tap the carb lightly with a hammer and it should ďfree it upĒ. It worked and you could hear the engine start to run properly. Off we went, found the ski that had previously been dropped and proceeded towards the marina. On the way there (approx 2-3 miles) the boat stalled around 1500 - 2000 rpm as I was slowing down for the narrows and also at the marina entrance.

Long story short, Iím assuming that the float is getting stuck open somehow. I have an inline Mercruiser spin-type fuel filter and the carb has a fuel filter, so I donít think that itís getting dirty fuel.

Iíve downloaded the carb manual (Service Manual #2) here:
http://forums.iboats.com/showthread.php?p=1693398#post1693398
and would like to trouble shoot it, but Iím a little hesitant in case I throw an adjustment off on the carb.

Are any of you familiar with this carb and/or have any advice?
Thanks!

Sidewinder
08-14-2009, 09:03 PM
Bump...

Any advice will be appreciated as the local marines are unable to look at the boat for quite a while.

Guys with '75 - '79's... what type of carbs do you have in your boats?

Thanks.

TMCNo1
08-14-2009, 09:23 PM
Bump...

Any advice will be appreciated as the local marines are unable to look at the boat for quite a while.

Guys with '75 - '79's... what type of carbs do you have in your boats?

Thanks.


Most all would be Holley or Quadrajet 4 bbl carbs
.

thatsmrmastercraft
08-15-2009, 01:44 AM
My '77 was repowered with a mercruiser with the same carb. I replaced the intake with a 4 barrel intake from summit and a 4160 Holley. Your set up is a very trouble free set-up when operating correctly. Sounds like the float is hanging up or the needle and seat isn't seating properly or not secured properly. I had a needle and seat come disconnected on a similar carb in an automotive application and it dumped the fuel through as fast as the fuel pump could push it through. If you don't have the ability to go through the carb, you should definitely have someone resolve the problem before you go up in smoke. A carb kit should only be $20 or so.

Sidewinder
08-16-2009, 08:33 PM
I took the top off of the carb yesterday and discovered that the internal carb filter (brass coloured nut located left of Mercruiser tag in 2nd pic) was half-full of calcium / sand-like deposits resembling the colour of Caribbean sand. I would have expected that the external Mercruiser fuel / water filter (similar to 2nd pic down here http://www.ebasicpower.com/c/MER7E/Fuel+Filters+for+Mercruiser ) would have removed the particulate. I guess not. Also noticed some "sludge" in the bottom of the carb - more than I would have expected from having a carb kit installed this spring and only having run 4-5 tanks of fuel through the boat since then. On that note, I always try to go nlt 1/4 of fuel iot to avoid sucking and sediment/water and/or having issues with running out. I cleaned everything as well as I could and removed the float / needle and everything seems okay now. We'll see when I fire it up in a few days.

Anyway, the external filter was changed within the last year by the previous owner. I'm guessing that moving the boat from a small, flat lake to a larger, rougher lake may have dislodged some sediment in the bottom of the tank.

Is there a better filter that I should be using? Should I install a Raycor fuel filter with a clear bottom? My parent's 1970 30' Trojan has them and they work flawlessly.

Fuel Shutoff: Is there one? Where is it located?

I've attached a couple pics of the internal area and underside of the carb along with the sediment discovery from the internal fuel filter.

Mr. Mastercraft,
Did you notice much of a difference in performance going from the 2 to 4 barrel setup? Carb kit was replaced in the spring. I'm surprised who strong the boat actually is for just a two barrel car - when it's running correctly! ;)
It has been almost 20 years since I took a carb apart, so I was somewhat hesitant. Turns out that conducting an an inspection / cleaning wasn't as complicated as I thought.

TMCNo1
08-16-2009, 08:52 PM
It appears the intake has a adapter under the carb for the 2 bbl. use. I suspect if you took off the carb and adapter and measured the bolt spacing, a 4160 Holley would bolt up using the 4 bbl. spacer normally used for the PCV valve as with the 4 bbl.. But, I would verify everything thru someone like http://www.skidim.com/contactus.asp first before sinking dollars into it.