happy hours

I installed anew long block about 15 hrs ago ( stock ) and last night took boat out ant in no wake zones would develop a miss after a bit . Seemed to idle fairly smooth, and if I advanced throttle it pull clean and ran fine . Its stock 350 with thru prop exhust and (a Holley 4175 vac secondary carb. When I started it that morning I pumped throttle a couple times and it backfired once but then started. What are symptoms of hurt power valve? Can backfires still hurt those? One terrifying thing is at ramp whe n I rise up and went to get truck when I retsrateted it turned hard for a split second then started and I thought maybe water in cylinders. But started fine at house to flush it and I started it 3 more times since and no issues and cranks fine. I had underwater lights and stereo running so may e just battery was drawn down ). Exhust is about 1.5yr old and tested it with alchol when I did motor. Sorry for long post.

AllDodge

iTrader: (1)

With a low speed miss and a backfire I suggest checking the timing, then pull the plugs and see what they tell you

Baja Rooster

iTrader: (1)

Could be timing. Could be reversion from a bad/loose exhaust manifold gasket. When my carb was too rich it had a miss at idle.



Edited: failed comprehension on my part

Powerquest230

Might recheck your exhaust, a small leak at idle could cause a miss that would clear up with more exhaust pressure.

getrdunn

iTrader: (7)

Sounds like could be bad power valve in carb.

happy hours

Just started it and cranked fine and ran it on the hose for a bit. It seemed like it loaded up and idled rough. If could advance the throttle and clear it. Ran it till it warmed up and then let it idle a bit and **** it off without clearing it. I will pull plugs tomorrow and see if they are sooty or worse wet.

mike tkach

iTrader: (3)

the symptom,s sound like reversion.did you pressure test the exhaust system?

Baja Rooster

iTrader: (1)

FWIW, if I pull the plug out of my O2 bung it's shocking how much water squirts up out of the hole, but when I leave the plug in and kill it first the plug comes out dry and sooty. That just demonstrates how much a leaking exhaust gasket could also suck up some water. With the backfire up through the carb though I'd guess the PV is dumping huge gas in there flooding it at idle.

happy hours

I didn't pressure test the exhust. To make story longer, the old motor got water in cylinder number one and at first suspected failed exhust. Pulled them off intact (risers in place) and filled them with water and never leaked. Hooked up water and pressurized clock and exhaust port around valve guide on one leaked. ( motor had 1600hrs of salt sayer use so assumed head errorded ). Manifold and riser surface a were clean and flat and overall they looked ok, but they are GLM and I know some peop,e hate them. I guess I will pull carb apart and replace PV to eliminate that.

happy hours

Good to know, so if I am following even if plugs are sooty I may still have a lake?