motor help

[Tresguey]

i took my boat out the other day. it starts easy and idles well, but if i half throttle it, the thing wants to die, but when i hammer down runs like a champ. i don't get it. it ran great before and i changed nothing on it. :idea:

[GasGuzzler]

Check (or change) the air filter and fuel filter to start with. Eliminate simple stuff first. :)

[BUSBY]

When was the last time you went through your carbs? Are you running a 4 bbl? Possible that your carbs are getting gummed up?
I had that problem on the old lake boat ... that was my problem ... but I hate carbs ... thats why I run injection! :D

[BUSBY]

Check (or change) the air filter and fuel filter to start with. Eliminate simple stuff first. :)
Good idea ... but wouldn't clogged filters show across the powerband, regardless of 1/2 or WOT? :idea:
But as he said ... check the simple stuff first ... most likely not your coil ... usually they're fine @ 1/2 throttle and go away under heavy load if they're going bad ...

[Tresguey]

plugs, wires, fuel filter, cap, rotor were all replaced in late july. i run the boat two to three times a week. however i did replace the wires again a couple weeks ago (because some feel onto the headers) and screwed up the routing of a couple wires and had a mean back fire. i an currently running a Holley 750 single pump carb. think the power valve may be messing up? i thought about that but figured it was something else because i can hammer down at idle and it tach's up with no problem.

[Squirtin Thunder]

Good idea ... but wouldn't clogged filters show across the powerband, regardless of 1/2 or WOT? :idea:
But as he said ... check the simple stuff first ... most likely not your coil ... usually they're fine @ 1/2 throttle and go away under heavy load if they're going bad ...
Going on this theory I would say check your fuel presure. I had a Camaro with a sbc mech fuel pump that did the exact same thing !!!

[Squirtin Thunder]

plugs, wires, fuel filter, cap, rotor were all replaced in late july. i run the boat two to three times a week. however i did replace the wires again a couple weeks ago (because some feel onto the headers) and screwed up the routing of a couple wires and had a mean back fire. i an currently running a Holley 750 single pump carb. think the power valve may be messing up? i thought about that but figured it was something else because i can hammer down at idle and it tach's up with no problem.
I would just replace the power valve for peice of mind !!!

[GasGuzzler]

Water in my fuel does some weird stuff, idles ok, stumbles midrange and runs ok wideopen. Air filter needs changing stumbles midrange to wideopen but idles fine, just thought that would be the simple stuff to start with before you go tearing stuff apart ;) so I just change both once a month.

[Squirtin Thunder]

What lake do you run at Gas ???
James, Norman or Mountain Island ???

[mrossum]

definately power vavle.

[1978 Rogers]

I blew my power valve a couple years ago from a backfire. I had your same syptoms. Idle & wot were fine, but it ran like shyt from 2800-3500 rpm.

[Tresguey]

i use a huge fuel filter/water seperator, and just a screen for air cleaner. i will change the power valve and go from there.

[GasGuzzler]

What lake do you run at Gas ???
James, Norman or Mountain Island ???
We have a place on High Rock Lake which is in Lexington NC but been to most of the others. Hooked up and heading down now...Tuff 25 minute ride :cool: