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carb goes dry

stupidbaker57

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Well I have got the boat in the water after a total rebuild of engine and boat. Now for the sea trails. The original carb (Holley 750 mech sec,) wouldn't let the engine idle, it would run lean. I borrowed a 750 Demon from my son and now the boat idles and ran nice for the first 3 or 4 miles of use at low to mid speed. Now at 1500 rpm or so sustained speed, the primary carb bowl goes dry. (sight glass). We thought the fuel pump (that was on the boat when I got it) was weak, so we changed it to an airtex pump that was larger. Same thing. The front bowl goes dry. This carb gave my son no trouble while on his blown 400 sbc. I was thinking that the float might be sticking at the top, but with the engine vibration could it happen?
 

2FORCEFULL

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Well I have got the boat in the water after a total rebuild of engine and boat. Now for the sea trails. The original carb (Holley 750 mech sec,) wouldn't let the engine idle, it would run lean. I borrowed a 750 Demon from my son and now the boat idles and ran nice for the first 3 or 4 miles of use at low to mid speed. Now at 1500 rpm or so sustained speed, the primary carb bowl goes dry. (sight glass). We thought the fuel pump (that was on the boat when I got it) was weak, so we changed it to an airtex pump that was larger. Same thing. The front bowl goes dry. This carb gave my son no trouble while on his blown 400 sbc. I was thinking that the float might be sticking at the top, but with the engine vibration could it happen?

yep, pull the needle and seat....

watch out,, you can burn a piston/
 

rivermobster

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Sounds like your fuel tanks are full of crap, and plugging up any carb you will use.

You have a bit more rebuilding to do. As Steve said, be careful. Running lean is a good way to destroy an engine. :(
 

stupidbaker57

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You're right! I could burn a piston. The engine that came with the boat had a hole burned through one of the pistons. Now for the info,,,,,,,new engine block, heads, intake, carb, dist (from points to ecu) The needle has been out a nuber of times and the float level set but it still runs dry. I'm goig to pull the bowl off and see if the float is hanging up in the closed position. If not,,,,,,,I'm stumped.
 

stupidbaker57

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Well,,,, because the carb is not mine,,,,I didn't open it up to check the float, so instead I rebuilt the 750 holley that came with the boat when I bought it. Be fore the carb ran lean and wouldn't idle without the choke on a little. Now that I rebuilt it, it idles and revs and gets back on idle after a rev, sooooooooo this Sunday I'll know more but I think the demon carb drank more than the pump could supply. I knew a girl like that!
 

CampbellCarl

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Like was already said/questioned, what have you done with the tanks? Are they fiberglass by chance? If so, they gotta go as they are delaminating and gunking up the fuel system.

If not glass, did you pull, drain and clean/flush them?
 

obnoxious001

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Like was already said/questioned, what have you done with the tanks? Are they fiberglass by chance? If so, they gotta go as they are delaminating and gunking up the fuel system.

If not glass, did you pull, drain and clean/flush them?

And where is the fuel filter, and when was it replaced, or what does it look like at this point?
 

stupidbaker57

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Here's an update to the dry carb. I rebuilt the holley and after a number of runs, it doesn't dry out, so I guess the demon was very thirsty. This boat has been completely gone through and renewed. The tanks are new (I built those too) fuel filter new, engine new, stringers and paint and seats and blah blah blah. Sorry I didn't get enough info out the first time about the boats' condition. Now that it seems to run ok, I'm now working on fine tuning and cav plate settings. I've had it up to 60 mph so far (12 degree 15% OD) and still have more motor left.
 

poncho

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Good news, i'd still want to play with that Demon and find out what's up. Dave, PM me and i'll give you my intial settings and we can screw with it when i get back....have fun.
 
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