www.iFourWinns.com

I have a 5.0L carb'ed OMC cobra (ford 302) and I think I am having some sort of fuel issue causing the engine to stall.

It is worse under load and will totally cut out but fire back up after turning the key off and back again. I change the fuel filter every year but I think I could be getting junk from the old fuel lines going to the fuel filter and then into the carb. I am mechically inclined but don't think I have the know how to clean and put back together a Holley 2barrel carb.

My plan of attack is to run the engine off a spar tank with clean gas. Does anyone know what size fuel line I need to hook up to the fuel filter? 3/8? I will replace the fuel filter before I do this test to eliminate any junk that could be in there.

I want to replace both fuel line and any anti-siphon valves....any idea what these are (sizes, PN, etc). This stuff isn't covered by my seloc manual.

Thanks everyone!

Also...where can I get a high quality carb kit? Sierra sells one as reference on MarineEngines.com but didn't know if there was a better source (ebay, amazon, etc).

I definitely want to get one that can withstand the E10 gas we have here in CT.

Is there a way to identify by markings on my carb if I have a 30cc or 50cc accelerator pump in it? I want to be sure I get the correct sized kit made for E10 gas

Direct from VP or Holley. Make sure the accel pump is green not black or it's not e10 friendly.

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1981 Columbia 8.7
2015 Yamaha FZR - 87mph - sold
2006 Yamaha GP1300R - sold
2003 Chaparral 215 SSI - sold
2009 Stingray 195CS - sold
2000 Four Winns H180 - sold
1976 O'day Daysailer II - sold
Rick's Four Winns H180 Mods/Upgrade Thread

So did some work on the boat today with good results!

I decided to change the fuel filter and run the boat of a spar 6.6gallon portable tank that I had. That tank is CLEAN and I put in fresh gas with some stabilizer in today. The boat ran great with these two changes so it makes me feel as if my main problem is fuel coming from the tank. Since our lake is so small I think I will just live with the small gas tank and then this fall I will pull the gas tank for a full clean out. At that time I will also change all of the fuel/fill/vent lines on the boat since I am sure they are original.

I got the correct carb kit (one for gas wth Eth) but I don't think I need to tear into the carb at this point. Might be a nice winter project if I feel the boat still isn't performing at its potential.

Sooooooo this little issue hasn't gone away. Here is where we are since list last post:

1) Rebuilt the carb. Nothing looked bad or broken but now we can confirm all the passages and things are clean.
2) Still running of the portable tank. In the fall I did take the main tank out to clean it. Put in a new pickup and anti-siphon valve along with new fill and vent lines. All of that should be good to go but I haven't filled it yet since I hadn't run on the rebuilt carb till today and didn't want too many variables if there was a new issue.
3) Outdrive u-joints and gimbal bearing were redone but don't think that helped or hurt anything.

I have a stalling issue under load but today I was able to (while someone else looked down the carb) recreate the problem while in neutral. If I go from a slow idle to putting the throttle on fast (like I am pulling a skiier) there is a large quantity of fuel flowing into the carb and then it will stall almost right away. It is acting like it is getting too much fuel and getting flooded. Once it dies it can be restarted but it will run rough for awhile. I can accelerate slowly to get on plan and take it up to full throttle without any issue. Once it is up and running at speed it has no problems running there. It just doesn't like the quick throttle change.

Could this be a power valve issue allowing too much fuel? I put in the power valve that came in the kit (not sure the size?). Or a different kind of vacuum leak causing too much fuel draw into the carb? We even suspected there could be an issue with the deceleration valve that would cause too much vacuum to be drawing through the carb. That is really the only vacuum like that gets hooked up the intake/carb on my engine.

Thanks as always.

Might be worth a read to decipher whether you have the correct nozzle size:

viewtopic.php?f=11&t=12641&hilit=accelerator+pump

Oh & I assume your engine's timing is set to specification & plugs are gapped correctly?

_________________
2011 Four Winns H180 SS.
Aussie built Mustang 2800.
SOLD - 1997 Four Winns Horizon RS

I'd agree with Defwish, if your fuel is pumping you need spark. If you plugs are old or incorrectly gaped it could be bogging down as the spark is not able to ignite the fuel, also ensure they are the correct plugs for the motor, then if timing is out you could have similar issues. Both simple and cheap to check to at least eliminate them.

_________________
Cheers

Mark
Melbourne
Australia

Boats:
Current: 2004 FW 190
2001 Mastercraft X5
1998 Malibu Response
1999 Sea Ray 180
17 ft Scimitar Barefoot (200hp Yamaha)
16ft Scimitar Ski (Yamaha 115)
1988 Ski Nautique ( Called Ski Antique)

^This.

_________________

1996 205 Sundowner DLX
5.0FL Volvo SX Cobra
Tow Veh: 2012 Nissan Frontier Pro-4X

We haven't checked the timing yet. We did pull the cover off the distributor to check that all the mechanicals of the spring advanced were moving freely and the springs were working correctly.

Where can I find the proper spark plug gap spec? I can't find it in my Seloc manual.

I don't have a timing light...wasn't born in the era where that was a standard tool to have. Suggestions? I am sure there are plenty of good youtube videos to show how it is done.

Why would the timing just "go out". We didn't have this issue when we purchased the boat. This thread was in the search of a stalling when "hot" issue and the coil being replaced was definetly the culprit.

In search of that we did change the plugs, wires and distributor cap so those are all fairly new. I could check the wire resistance to make sure they didn't get damaged somehow and that the plugs are properly gaped (found it in my manual finally).

If my issue is NOT timing or spark related then I would suspect my issue is TOO MUCH fuel flooding the carb when full throttle is applied fast. Vacuum leak? Miss sized accelerated pump cam? idel mixture screw making it too rich? miss sized power valve?

While doing more research on this on a different forum someone brought up that the power valve might not be correct. I did replace the existing PV for a new one that came in the rebuilt kit (a 3.5).

Now when seeing what Holley states should be the size of the PV they say take the idle vacuum reading, divide by 2 and that should be the size of the PV. Would the same thinking be for a marine engine as a car? Could my issue be that my power valve stays open too long (because I have more vacuum then 7"Hg) causing a too rich condition under load?

Thanks.

Well I got time this afternoon to get to the boat (hr away) and dive into this issue. Here is what happened and what I think we have learned.

1) We checked the timing and it was correct at 10def BTDC which is what the manual suggests at idle. It seemed to advance as it was supposed to at higher RPM. Doesn't seem to be the stalling issue.
Result: Boat still stalls under quick throttle

2) Checked the vacuum on the engine and when the engine starts it goes up to around 17"Hg which it on the end of the "good" range for vacuum pressure.


After it idled for a bit it ended up settling around 18.5"Hg


This PV doesn't follow the generic convention people use for Holley carbs so we thought we would start there to try things.

3) We swapped out the power valve (what I think is a 3.5 since the markings are UN-READABLE!) for a power valve (PV) plug. That totally takes the power valve out of the equation. The engine did NOT like that and it ran like crap at idle and barely could stay running. Stalled when you tried to give it even the smallest bit of throttle. This was not the answer.
Result: Going to PV plug did not help at all (made it worse).

4) My uncle had a 6.5 PV from his car so we decided to give that a try and you could feel the physical difference in the springs stiffness between the 3.5 and the 6.5 (with the 6.5 being much stiffer). We swapped that in and then started the engine up. At first it seemed to idle rough (looping?) but we adjusted the idle speed and that seemed to smooth it out. At that point I tried hitting the throttle hard and it worked! It was able to rev really fast and get there quickly where it would have stalled before. We even noticed that maybe the jet spray looked more uniform?
Result: Going to a 6.5 PV seems to solve stalling at quick throttle issue (but made it not idle well).

4) Then we went then to try to get the idle speed to be within spec and get the engine to run smooth at idle, it was running very lumpy/surging. We put the idle mixture screws to the seat and then backed them both off to 1 turn off the seat (manual spec). The engine did not run better and we could not get the engine speed to the 550-650 RPM without stalling. We then played with the screws between 0 turns and 2.5 turns out and it seemed to be the best at almost seated (1/4 turn?). What was more strange was that it didn't seem to make a difference in how it idled from 1 turn to 2.5 turns...like those screws weren't doing anything?
Result: Couldn't get boat to idle at speed and smoothly by adjusting idle screws with 6.5 PV

So where do I go now? Our thought was to get the carb back to stock as close as possible since it doesn't like to idle anymore and that is no good. It has currently #71 jets and the spec is 72 so I was going to purchase those and swap those in when I put the 3.5 PV back in. If that doesn't work what would I try next? A 8.5 PV? (18"Hg/2=9) The only other werid thing is we could hear the engine make a small noise ("tis" "tis" sound and it we noticed the vacuum gage needle drop when we heard the sound. I tried to take a video of the sound. It is mostly heard from the left side of the engine. Maybe the exhaust flapper is stuck/busted causing issue?


Thanks for everyones help and suggestion!

So i am feeling defeated. I took the carb apart and went back to stock (3.5 PV, 72 jets, orange cam). At first I had a hard time getting it to idle at all when setting the idle and idle mixture screws per the spec. I really had to work at it to get the RPMs where they needed to be but the idle screws were way more open than 1 turn from seat.

I eventually got it to idle but it was rough and was only getting 11-12"Hg on the vacuum gage now which is werid becaues I had much better vacuum previously. I did a voltage drop test to check the ignition side but that was all within spec.

I decided to take the boat to a professional...says he will get to it later this week. Wish I had more info to share.

:-/

Boat is back from the marina today and we should be good to go for the 4th of July weekend! Tech at the marina started going over the boat looking at other things besides the carb since I had just gone through it (new carb kit not just cleaned). They checked compression and all cylinders checked out. They determined that it was definitely fuel related so they wanted to pull the carb and go through it themselves.

They said they found debris in the carb (weird) and said it was strange to them that all the gaskets seemed to be swollen? Like they had been absorbing moisture/gas. They think that is what they were seeing in the carb passages and that maybe I got a rebuild kit that was a lemon? They cleaned everything up and put in a new carb kit and they said that made it run 90% better.

They noticed one plug was an autolite and the others were champion and the autolite seemed old and fouled. They replaced it with a new autolite and they said that made the difference in how it would run.

I am going to spend sometime on it this weekend and really see if it is running as good as it used to. If it does run good I'll move it off the portable tank and back to the larger clean main gas tank.