Bigdaddydean
08-29-2018, 01:21 PM
I have a 99’ mobius. 5.7 Indmar assault 310 carbed with the 75021.
So as not to waste too much time here I’ll get right to the short and sweet of it. I sent my carb off to get rebuilt by a carb company in Florida. First of all. I was very reluctant to send it to anyone as this being a proprietary carb a lot of Holley people think these are just like any other Holley. I know they are to a point with some very different characteristics. I have rebuilt this carb 2 other times with no problems. This time it was due for replating and a rebuild. This is why I didn’t do it myself. So now the problem....put it on the boat and it won’t start without first giving it some throttle (new issue, never had to throttle boat prior to starting, ever). After initial starting very irratic idle. I have to adjust the idle screw to idle at around 850-900 rpm. It can idle for 1/2 hr this way and still be probematic until I get under way and really open it up for a moment
Then when I go back to neutral it’s idling way too high. Like 12-1300 rpm. If I adjust it back down that’s fine while
It’s running but as soon as I turn it off and let sit for any length of time it’s right back to square one.
I am very mechanically inclined but for the life of me I can’t remember if this carb had a fast idle setting or not. It def. has th idle cam behind the Choke but no screw or anything adjustable behind it. I’ve set the choke to where it was prior to rebuild. I took the float bowls off to make sure I have the correct jets and power valve. That’s fine. My plugs are new as are the cap and rotor. I’ve checked that all cylinders are firing and compression is good. Boat runs top notch when warm. Just cannot get the slow/cold idle right. Oh and no vacuum leaks and mixture screws are at 1,3/4 turns out for just a hair above 20lbs Vac.
Any thoughts?
So as not to waste too much time here I’ll get right to the short and sweet of it. I sent my carb off to get rebuilt by a carb company in Florida. First of all. I was very reluctant to send it to anyone as this being a proprietary carb a lot of Holley people think these are just like any other Holley. I know they are to a point with some very different characteristics. I have rebuilt this carb 2 other times with no problems. This time it was due for replating and a rebuild. This is why I didn’t do it myself. So now the problem....put it on the boat and it won’t start without first giving it some throttle (new issue, never had to throttle boat prior to starting, ever). After initial starting very irratic idle. I have to adjust the idle screw to idle at around 850-900 rpm. It can idle for 1/2 hr this way and still be probematic until I get under way and really open it up for a moment
Then when I go back to neutral it’s idling way too high. Like 12-1300 rpm. If I adjust it back down that’s fine while
It’s running but as soon as I turn it off and let sit for any length of time it’s right back to square one.
I am very mechanically inclined but for the life of me I can’t remember if this carb had a fast idle setting or not. It def. has th idle cam behind the Choke but no screw or anything adjustable behind it. I’ve set the choke to where it was prior to rebuild. I took the float bowls off to make sure I have the correct jets and power valve. That’s fine. My plugs are new as are the cap and rotor. I’ve checked that all cylinders are firing and compression is good. Boat runs top notch when warm. Just cannot get the slow/cold idle right. Oh and no vacuum leaks and mixture screws are at 1,3/4 turns out for just a hair above 20lbs Vac.
Any thoughts?