Carb questions

Patchman

Patchman

Administrator
Staff member
A double pumper wouldn't be necessary for your boat to run. If the secondaries aren't opening, that could be the problem. All you have to do is watch them while someone else runs the boat. They should open up fairly quickly when full throttle is applied. May just have a bad secondary diaphragm. think.gif
 
J

jimsplace

Active member
Yea, what patch says.
For how it's being used, I would think a vacuum secondary would be the preferred carburetor to use.
    :smile17:
 
C

customtouch

Active member
I agree with Patch and Jim. I think the carb you have ( when functioning properly ) would out perform a double pumper in your application. I think you have the right carb you just need to be sure it's right. If it is working correctly I would spend my money and time trying to prop it right for the boat/motor combination you have.
 
J

jimmyray0682

New member
Thanks guys. I took the boat out today and sure enough yall were right the secondaries were not opening. When I manually opened them it was a whole new boat. I put the boat where it was just under plane and opened the secondaries and it immediately planed out and took off. So I'm gonna order a new diaphragm and see what happens.
 
C

customtouch

Active member
jimmyray0682 said:
Thanks guys. I took the boat out today and sure enough yall were right the secondaries were not opening. When I manually opened them it was a whole new boat. I put the boat where it was just under plane and opened the secondaries and it immediately planed out and took off. So I'm gonna order a new diaphragm and see what happens.
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If it were me, I would just go ahead and get a complete rebuild kit for it, clean it all and go through the whole carb while I had it off to be done with it. It does not cost that much more and is way cheaper than buying another carb like you were thinking!  Then you can move on to dialing it in without wondering if it's right!!  :smile30:
 
C

customtouch

Active member
Holleys are pretty basic and simple but if you don't feel comfortable rebuilding it doesn't cost that much to have it done professionally. It will be worth every nickel though to eliminate it as a problem and move forward.  :smile30:
 
C

customtouch

Active member
BTW, if it were mine and it didn't already have them, I would invest in a set of J tubes for it too while I was at it. It's a cheap investment in safety for an enclosed engine compartment.
 
J

jimmyray0682

New member
Rebuilt the carburetor. Put a weaker spring in the secondaries. It hurt more than it help, so I'm going back with the stock one. But all four barrels work now. But it turns about 4700 rpm now at wot.
 
J

jimsplace

Active member
The weaker spring is letting the secondary open too quick.  I don't think the vacuum operated secondary has squirters to cover the increased air without fuel.
It's largely a matter of trial and error to see what it likes.  It will tell you.
 
D

Disturbed

Active member
jimsplace said:
The weaker spring is letting the secondary open too quick.  I don't think the vacuum operated secondary has squirters to cover the increased air without fuel.
It's largely a matter of trial and error to see what it likes.  It will tell you.
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X2

 
Patchman

Patchman

Administrator
Staff member
Your prop ia also gonna dictate what you can spin WOT. Sounds like you have the carb figured out though! clap.gif
 
C

customtouch

Active member
DISTURBED said:
I would throw some more timing at it just to see if it likes it.  I'm betting it would like 38-39 total.
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While it is possible it might like that much timing, I would be very carefull to monitor the motor closely for signs of detonation.  IMO (which is almost worthless compared to Tim's mechanical knowledge) that sounds like a lot of timing for a basically stock 350 running on 90-93 octane fuel under the constant load found on an outdrive type boat. Mercruiser recommends 32 degrees total maximum if you go by the chart and add intitial. I ran 10 degree initial and about 32 total on the 350 in my Glastron with 93 octane and it seemed to like it & I felt pretty safe. The problem with an enclosed engine compartment is you can't really hear a problem if it's knocking a little until it's too late so just pay attention if you kick the timing up that much.
 
J

jimmyray0682

New member
I'm looking for some headers now. Got my eye on lightning water jacketed headers. Need some exhaust that'll clear my tall valve covers.
 
D

Disturbed

Active member
customtouch said:
DISTURBED said:
I would throw some more timing at it just to see if it likes it.  I'm betting it would like 38-39 total.
Click to expand...

While it is possible it might like that much timing, I would be very carefull to monitor the motor closely for signs of detonation.  IMO (which is almost worthless compared to Tim's mechanical knowledge) that sounds like a lot of timing for a basically stock 350 running on 90-93 octane fuel under the constant load found on an outdrive type boat. Mercruiser recommends 32 degrees total maximum if you go by the chart and add intitial. I ran 10 degree initial and about 32 total on the 350 in my Glastron with 93 octane and it seemed to like it & I felt pretty safe. The problem with an enclosed engine compartment is you can't really hear a problem if it's knocking a little until it's too late so just pay attention if you kick the timing up that much.
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I should've clarified.  Yes, definitely mind the possibility of detonation.  I would take baby steps up to that much timing.  How much compression are we talking about?
 
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