boatman747

Ok I got my motors back from the dyno shop 97 squared in the carbs . But wouldnt idle.So the question is if I lower the primary to maintain idle and increase the secondary side I shouldnt have a lean condition .At 87 squared it idles like a champ. Also can I pull power off the starter selenoid in front of the motor for my electric fuel pump ?

Vinny P

The pump should be powered from the battery through the appropriate fuse or breaker along with a relay and oil pressure switch.

mcollinstn

if the motor was jetted on the dyno, then leave the mains alone. They should be good (or at least close, since your boat exhaust will change it a touch from the dyno headers).

If you cannot get a good idle by playing with the mix screws, then check and make sure your power valve is "low" enough. They may be staying open.

mopower

Yeah like he said. Main jet should have no effect on idle. Idle screws effect idle and bad or incorrect power valve will effect idle

Griff

Jetting will have absolutly no effect on idle. Also check fuel bowl levels. If ones to high, it will load up at idle.

boatman747

I know ive been harping on these carbs for a while , A couple locals have the same and or bigger set ups and run 10 jetts smaller. 97 squared seems so exteme for a 540 and a dominator . The stock jetts are 87 squared and thats what they run. And they run over 600 cubic inch motors. Although what you say makes sense. Sounds like I might try a 4.5 power valve. The boat ran fine from 1200 rpms on but the idle screws were only one turn out. I will check the floats again . I checked idle screws last night.

PatriYacht

Check ignition timing. Modified engines with larger than stock cams need more initial timing. If you have a MSD set up, you limit the total advance with a bushing so you can use more initial. If you have Merc ignition, use the V6 module. It provides less total timing so you can use more initial.

boatman747

I have the v6 module . The boat ran great but in gear at idle its crap and in neutral it was crap. It only idled at abt 1200. But with 87 jetts it idled great but that was a 10 jett size change.

boatman747

do the mix screws have any effect when cruising or is that strictly main jetts and air intake

JIMG

Does it idle ok for a minute & then drop off ? If so it could be water reversion. the difference being on the dyno or in the boat.