SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: 69kona on May 08, 2016, 10:49:54 AM
-
This weekend boat ran fine on Friday at AVI , but Saturday it was different story. Any thing past 4500 rpm it would sputter and cut out .
Checked fuel filter was clean
Jets in carb were clean
Fuel pressure good
Any input ?
Sent from my iPhone using SoCal Jet Boats
-
Wet ignition, failing ignition coil, sticking valve, bad wire, loose connection electrically, valve/rocker/pushrod problem.
How I would handle finding the problem with the limited information.
Compression check.
Spark plug analysis.
Fuel jar check (looking for water/debris).
Timing check.
Pull distributor cap and check for oil/water.
After that, it gets tougher.
-
Cool Gt I'll start there ..
Sent from my iPhone using SoCal Jet Boats
-
If it runs fine below 4500 rpm I would still think it's something to do with fuel. Especially since it was running fine the day before. I'm not discounting anything GT says, I would follow similar direction after going over the fuel system again. I've had fuel filters cause this that looked fine, replaced and problem went away.
-
What ignition box? Does it have a Rev limiter? What's it set at? They're common to fail or be off quite a bit of rpm.
-
What ignition box? Does it have a Rev limiter? What's it set at? They're common to fail or be off quite a bit of rpm.
MSD box
Rev limiter set 6k
Sent from my iPhone using SoCal Jet Boats
-
MSD box
Rev limiter set 6k
Sent from my iPhone using SoCal Jet Boats
. I heard it Saturday morning not sounding so good. I know Dennis had a pill go bad before. Not sure you may have the dial type. If not pull the pill and it will clean up if that's the problem.
Sent from my iPhone using SoCal Jet Boats
-
Yuuuuuppp. I bet you a 12 pack that's the problem. If it's a dip switch aka dial type, max it out and see if it goes away. :-)
-
. I heard it Saturday morning not sounding so good. I know Dennis had a pill go bad before. Not sure you may have the dial type. If not pull the pill and it will clean up if that's the problem.
Sent from my iPhone using SoCal Jet Boats
Good idea 👍
I took carb apart everything looked ok
Sent from my iPhone using SoCal Jet Boats
-
If removing the pill doesn't fix it, it might be the box itself. I've had two go bad on me, with similar symptoms to what you describe: Engine miss-fired terribly above a certain RPM. Good luck.
-
Would av gas be a problem to run ? My buddy said he thinks it's my be the problem...
Sent from my iPhone using SoCal Jet Boats
-
Would av gas be a problem to run ? My buddy said he thinks it's my be the problem...
Sent from my iPhone using SoCal Jet Boats
That's possible too, really depends on where you got it. I get mine from the airport in Temecula and it works great, but I've used the AV gas from parker Oil in Parker and it ran like shit.
-
Would av gas be a problem to run ? My buddy said he thinks it's my be the problem...
Sent from my iPhone using SoCal Jet Boats
. If the AV gas is clean and know water it is fine to run. Have you checked your valves?
Sent from my iPhone using SoCal Jet Boats
-
. If the AV gas is clean and know water it is fine to run. Have you checked your valves?
Sent from my iPhone using SoCal Jet Boats
as a.
Nope not yet. That's my next step. I put my buddy's vacuum gauge on and it was normal. If it there was a big problem would it show on gauge?
Sent from my iPhone using SoCal Jet Boats
-
Depends on what the problem is.
Sent from my iPhone using SoCal Jet Boats
-
69kona, did you change the Rev limiter and put the boat back in the water and test it yet ??
-
69kona, did you change the Rev limiter and put the boat back in the water and test it yet ??
Not yet.... Gonna finish up new motor just incase
Sent from my iPhone using SoCal Jet Boats
-
I'm betting that it will take care of the problem. It happens often.
-
Going on 6 years on this motor that's in the boat now freshened up 2 summers ago should be something easy to fix.
If not
New motor has
Bbc rods
ICON Forged Pistons 10.5 to 1
Oil mods
And still a ticking time bomb lol
But I'm a dye hard olds lover screwy :)
Sent from my iPhone using SoCal Jet Boats
-
i run the same AV fuel you do from the same airport... Not the issue. Speaking of which, did you add marvel to it? How much?
Im betting its ignition somewhere
-
Pulled MSD rev pill out made it run alittle better still lacking rpms
Pulled plugs and they look little lean
Did compression test and have 155 psi in 7 cylinders and one at 145
Why lean?
Sent from my iPhone using SoCal Jet Boats
-
Motor used to be on rich side !!!!!screwy
Sent from my iPhone using SoCal Jet Boats
-
Maybe a fuel line collapsing do you have a fuel pressure gage to check it at rpm
-
Did timing somehow change ?
-
I checked timing..... Frustrating! good compression , vacuum was steady
Went through carb was all good
The only thing I found was rev limiter pill was bad....but still only revs to 4500
Motor usually spins 5100
Sent from my iPhone using SoCal Jet Boats
-
Maybe my ignition going out?
Sent from my iPhone using SoCal Jet Boats
-
Pulled MSD rev pill out made it run alittle better still lacking rpms
Pulled plugs and they look little lean
Did compression test and have 155 psi in 7 cylinders and one at 145
Why lean?
Sent from my iPhone using SoCal Jet Boats
So you pulled the rpm pill out, put boat in the water and tested right ???
-
Yep
Sent from my iPhone using SoCal Jet Boats
-
He pulled the pill out, put it in the water and the cutting out/misfiring is gone. But hes now down about 600 RPM. He was spining in the 5100 range before and ow the engine jsut cant pull past 4500
Im thinking fuel delivery
-
Hmmmm that's interesting
-
https://youtu.be/z4sSwRcyGAU
She got the new motor put in that I have been building...
Sent from my iPhone using SoCal Jet Boats
-
Nice
Sent from my iPhone using SoCal Jet Boats
-
Nice
Sent from my iPhone using SoCal Jet Boats
Thanks bud!
Sent from my iPhone using SoCal Jet Boats