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ggrimes13
05-20-2013, 01:58 PM
I think I have a carb issue but not sure. 1987 Tristar, 351 rebuilt with GT40 heads (before I bought it last August - I since verified the 3 ribs in head casting after learning that here in TT). Also "new" rebuilt Holley 4160 (part 80319 - by an aftermarket rebuilder). 50 hours on the overhaul. Motor would start only by pumping throttle, then would not idle below 1300 rpm cold. Once completely warmed up, it would idle in neutral and run OK except for some hesitation on acceleration.

While out for the off season, here's what I did: replaced points/condenser/coil with Pertronix Ignitor III & Flamethrower coil, set timing, replaced plugs with Autolite 764 (per info found in TT for GT40 heads). Then while waiting for spring to arrive, took time to go through the carb to check all settings. I couldn't find a spec for float height (sheet with rebuild kit 703-47 did not have it), so I set them parallel to bowl, installed the carb and cranked to fill bowls, then used the secondary bowl sight plug hole to check and adjust that side, then set the primary (which does not have the hole) the same.

Now it rarely idles at all, usually dies when going below 1200 RPM even after completely warming up. It did idle two times, allowing me to take it out for a test run (I live on a lake), and it acted the same as last year in regards to hesitation on acceleration. Working on the idle issue, I've tried adjusting the idle mixture screws both ways without success. Yesterday it wouldn't idle at all. Any advice on where to go next with the troubleshooting?

ggrimes13
05-20-2013, 08:00 PM
I'll add a little more info, still looking for suggestions. I changed all fuel filters. End of last season I added Seafoam then topped off the gas tank. Dist cap and plug wires were replaced by PO at the overhaul so I did not replace.

thatsmrmastercraft
05-20-2013, 08:17 PM
You might be dealing with a base gasket vacuum leak causing a lean condition. You may have some debris in the system that is not allowing the needle and seat to close completely when they need to producing a too rich condition. Are you seeing any black smoke or any soot build-up on your transom? Might take a look at a spark plug or two to see if they are black indicating too rich.

Post a pic or two of your carb as I suspect you may have an automotive carb on your boat. There are some marine Holleys with fuel bowl plugs but they didn't come on a MC.

Cloaked
05-20-2013, 08:24 PM
http://www.mastercraft.com/teamtalk/showthread.php?t=54417

.

ggrimes13
05-20-2013, 10:00 PM
Thanks for the feedback MrMC. I'll try to get some pics of the carb Tuesday after work, and pull plugs to check condition. And thanks also Cloaked for the link to a similar issue. My carb was incredibly clean having only 50 hours on it, but there's something wrong somewhere so I'll watch this thread for his results.

ggrimes13
05-22-2013, 10:39 PM
Pic of the carb installed by PO:
95437
Peeled off the sticker:
95438
After seeing this, decided I wasn't in the mood to spend countless hours tracking down what might be wrong with this carb. Better for me to start over with a NEW carb from Holley. Found a dealer not far away and order for 1-day delivery. Received this carb today:
95439
Installed, fired up, and runs great! Minor adjustments to idle mixture screws and RPM, took her out on the lake and seems all is well...I couldn't be happier!:) Now I can enjoy the long weekend instead of working on this...:toast: Thanks for the advice, in some ways I feel like I took the easy way out, when I was a younger man I wouldn't have caved in so easily. But at the age of 53, I just want to have fun with my kids and grandkids, not spend all weekend trying to get the boat running.:dance:

j.mccreight@hotmail.com
05-22-2013, 10:42 PM
Glad you got it fixed, I have heard terrible things about national carburetor...

Lumbergh
05-22-2013, 11:21 PM
http://i470.photobucket.com/albums/rr66/Lumbergh556/happy-endings.gif (http://s470.photobucket.com/user/Lumbergh556/media/happy-endings.gif.html)

Nice!

thatsmrmastercraft
05-23-2013, 01:00 AM
Good to hear that you are back in business.

ggrimes13
05-23-2013, 05:55 AM
a couple more pics for those interested. the rebuild from National Carburetor had a sight plug hole on the secondary bowl, and the choke vent was closed off with epoxy:
95451
The new Holley as no sight plug (per your comment mrMC) and a proper screen on the choke vent:
95452
Now that I've taken the time to read the FAQ on how to post pics, I find it rather fun to participate. I'll share some of the other things I've done on the appropriate thread. Thanks again for the advice and happy boating to all!:D

thatsmrmastercraft
05-23-2013, 08:41 AM
a couple more pics for those interested. the rebuild from National Carburetor had a sight plug hole on the secondary bowl, and the choke vent was closed off with epoxy:
95451
The new Holley as no sight plug (per your comment mrMC) and a proper screen on the choke vent:
95452
Now that I've taken the time to read the FAQ on how to post pics, I find it rather fun to participate. I'll share some of the other things I've done on the appropriate thread. Thanks again for the advice and happy boating to all!:D

Great job on the pics. We are always happy to have another active member with the capability to post.

It is interesting that the National carb comes with a sigh plug. I suppose allowing customers to dial in the float level saves on returned carbs that won't work due to the float being set too high.