Rochester Carb Adjustments

[WaterLauger]

I have a '74 Crestliner with an OMC245 and Rochester 4MV carb. I recently put a new motor and tested out on the hose - idled fine and revved nicely.<br /><br />Put her on the water this weekend and idled past the 5mph markers. When I gave her a little juice, I couldn't come up past 2k rpm. Put it in neutral and revved fine. I am not the best carb guy but I think my recently rebuilt carb isn't doing its thing under load.<br /><br />What types of adjustments am I missing? Does this sound familiar to anyone?

 

[sea wolf]

Re: Rochester Carb Adjustments

i'm not sure about a carb adjustment, but why are trying to rev it past 2krpm when running off the hose? you're asking for trouble, in my opinion.

 

[William B Arthur]

Re: Rochester Carb Adjustments

Yep, sounds EXACTLY like what mine is doing. I am really really hoping its the float height. Look, another guy with a 229 is having the same problem, all of us after rebuilding the carb. I should be able to tell in a little while if the new float height solves the problem or not. I just have to put the carb back on the motor and get to some water to see. Mine will rev somewhat in the yard, but still isnt right, but wont plane or do anything in the water.

 

[WaterLauger]

Re: Rochester Carb Adjustments

Good point Sea Wolf. I forgot to mention that I also dipped the outdrive in a modified plastic trash can full of water. Better safe than sorry.<br /><br />Wild Bill, keep me posted on what happens. I pulled it all apart on my bench and noticed that my vacuum line going to the choke diaphram was worn. Although this isn't a choke problem, I thought the old line would affect my throttle body vacuum as well so I replaced the line. I also noticed some air/fuel lines inside the carb that were being limited by debris so I blew those out as well. Can't wait for a clear day. I need to get up to speed....

 

[horndog]

Re: Rochester Carb Adjustments

what do you mean it doesn't go past 2k? does it crapped out and die or does it think thats the farthest the throttle goes?

 

[WaterLauger]

Re: Rochester Carb Adjustments

It will accelerate to about 1500 fine then slowly to 2000. Then it just stays there while I peg the stick the rest of the way. It sounds different too. You don't hear as much of the carb sucking noise as at 1500. I can't feather it any further and I can't punch it to anything above 2000. Sound wierd?

 

[William B Arthur]

Re: Rochester Carb Adjustments

Yeh, I'll let you know. I am almost sure that is the problem though. (float height) I when I re-set the float, it brought the fuel level higher, which will make the motor run a little richer. Well, I still dont have the carb on yet, but I was doing a compression check last night, only got one side of the motor done before it was too dark to see, but all three of those plugs had a super shiney white insulator. Sure sign of a lean condition/pre ignition. BTW, the compression was all between 120-130 psi on the left side, I am going to check the other side just to be sure, but I dont think that is my problem. Doesnt hurt to check though.

 

[a.d.mobile]

Re: Rochester Carb Adjustments

Boys with engine off! remove spark arrestor have good buddy throttle boat look down carb do you see fuel squirting from 2 spots downwards into venturi? if not acculator pump is not working this will cause your grife. or if you just rebuilt carb did you put that tiny check ball in the bollom of the acc pump return spring passage? ball goes in the small hole with a small wire clip to hold it in place. this will cause same problem. good luck ad

 

[WaterLauger]

Re: Rochester Carb Adjustments

a.d.mobile Thanks for that. I think this may be a pretty stupid question, but what EXACTLY does that check ball do?