5.0GL-C won’t get on plane

[JR6424]

Yeah, I replaced that little mesh filter as part of the carb rebuild but I didn’t get a good look at it yesterday, maybe I should pull the carb and give it another thorough going through before proceeding further.

 

[QBhoy]

Ok, another new development. I still don’t have anyone to help but when I got home from work I tried starting it again and still no good. I pulled the fuel filter and it was about half full. I pulled the line off the carb and it was dry, then I pulled it from the fuel pump side and it sort of “popped” once it was loose and grimy looking fuel went everywhere. I blew out the hose with compressed air and reinstalled it on the pump and ran the other end into a clear container and cranked it and a steady stream of clean fuel came out. I reinstalled the line to the carb and it started right up.

I thought maybe I’d solved my problems, however when I rapidly advance the throttle it stumbles and sometimes stalls, plus there’s a steady tapping sound now that wasn’t there before. So I think my no start issue was a clog in the fuel pump outlet or line to the carb, but the lack of power under load problem probably still exists.

On Monday when I have help I’m going to reset the valve lash with the engine running and confirm the timing is set properly and that the timing advance system works. If I still have issues after that I’ll look at the accelerator pump lever and maybe put a fuel pressure gauge inline and see what my pressure looks like under load.

Am I missing anything else? Thanks for all the help fellas, it’s greatly appreciated.

Yeah. The carb clean you’ll likely now need

 

[Lou C]

There are also 2 other things that could be related….
Anti siphon valve on the fuel tank fitting & the screen on the pick up tube in the tank.
There may be a small screen in the carb inlet area with on Holley carbs (I think that’s what you’re working on) that you can check too….

 

[JR6424]

There are also 2 other things that could be related….
Anti siphon valve on the fuel tank fitting & the screen on the pick up tube in the tank.
There may be a small screen in the carb inlet area with on Holley carbs (I think that’s what you’re working on) that you can check too….

Yeah, it’s a Holley 2 barrel. The screen in the carb inlet was changed during the rebuild but it’s probably clogged again now. I have no idea how I would check the anti-siphon valve or fuel tank pickup tube screen as the tank is below deck and inaccessible. It’s like they put the tank in first and then laid the fiberglass over top of it.

 

[muc]

Yeah, it’s a Holley 2 barrel. The screen in the carb inlet was changed during the rebuild but it’s probably clogged again now. I have no idea how I would check the anti-siphon valve or fuel tank pickup tube screen as the tank is below deck and inaccessible. It’s like they put the tank in first and then laid the fiberglass over top of it.

Try reading this.

HOW TO: Testing your boats fuel system.

Note, this was originally posted courtesy of Don S. Minor edits and pictures added by CaptJason A lot of you folks out there seem to be tearing into carbs quite a bit. Before you choose to open up a carb, you really need to look at what's feeding the carb first, and that is the boats fuel...

forums.iboats.com

maybe one of the mods could fix this link in the sticky’s.

 

[JR6424]

Try reading this.

HOW TO: Testing your boats fuel system.

Note, this was originally posted courtesy of Don S. Minor edits and pictures added by CaptJason A lot of you folks out there seem to be tearing into carbs quite a bit. Before you choose to open up a carb, you really need to look at what's feeding the carb first, and that is the boats fuel...

forums.iboats.com

maybe one of the mods could fix this link in the sticky’s.

That’s a big help, thanks. My buddy just asked me if I’d checked the tank vent yet and mentioned the mud dauber nest thing. I haven’t checked that yet and I think it will be the first thing I do tomorrow when I get home. I’ve had them make nests in the “pee line” on my kicker motor before and even found one in the ignition key slot of my tractor!

 

[JR6424]

Ok so I replaced the fuel pump and did all the fuel system tests and everything seems to be in order on the fuel system side. I cleaned the screen on the carb inlet (looked clean) blew out the fuel line and the fuel tank vent line and there are no restrictions or obstructions. The fuel filter is brand new and the tank is full of 91 octane ethanol free fuel. The boat fires right up on first crank and idles great but still stumbles and backfires under fast acceleration.

I turned my attention to the ignition system, this is a brand new coil and brand new Delco EST distributor. I had already set base timing using the shunt tool but had not checked whether the electronic advance was actually working. I warmed up the engine and revved her up to 2000 RPMs and set the advance on my timing light to 26 degrees as per the timing curve posted above. The timing mark was nowhere to be seen. I slowly dialed back the advance on the timing light and eventually the mark lined up at 6 degrees advance. So either I screwed up the base timing setting or this brand new dizzy is faulty. I’ve watched all the YouTube videos I can find on this subject and read through the threads on here and I think I set the timing properly so I guess I’ll order a new distributor and see if that fixes things.

I’ll report back when the new dizzy arrives, any and all feedback appreciated as always!

 

[alldodge]

If anything its the module. The dizzy is just a mechanical device

 

[JR6424]

Agreed but the module came with the dizzy so I’m going to buy the exact same one and return this one if it fixes the problem.

 

[Lou C]

There has to be a way of getting at the connections for the fuel tank. Some boats like mine has a hatch that you remove, others have a circular pie plate cover that comes off to reveal the connections. My boat had a similar problem & it was the anti siphon valve which is what the fuel line from the pump connections to to.
I went through the ignition system & carb still had the problem and being new to boats took it to a good mechanic and that’s what they found. Replaced that part in 2004 & been fine ever since!

 

[JR6424]

A new ignition module fixed the problem folks. I ended up getting a Sierra Marine ignition module and installing it in the distributor I got from Amazon and now everything is working fine. I checked the timing advance with the old module and no matter how I set the base timing it always seemed off by about 10 degrees. At one point with the shunt tool in place and my timing light on I could actually see the timing mark move around from about 0 to 10 degrees BTDC while the distributor wasn’t even loosened yet. With the new module in the existing distributor everything worked without even having to readjust the base timing. It follows the curve posted above here in this thread by AllDodge exactly and now the boat gets up on plane easily and maxes out at about 4300 RPMs at WOT which I could probably improve on if I learned how to tune my carb and work my trim systems better. I still have a few minor issues here and there but I’ll save those for another thread. Thanks to everyone for the help!

 

[JR6424]

For the record the distributor with the faulty ignition module was this one:

EST Marine Electronic Ignition Distributor V8 5.0 5.7 7.4 18-5484-1 18-5514 3857449 for Mercruiser EFI Chevy Chevrolet Volvo Penta OMC

Compatible with Chevy inboard and i/o. Fully electronic including advance and timing setting. Has the necessary parts to allow your Alpha1 or Cobra outdrive (if so equipped) to shift as it does now! KIT- 18-5514, DISTRIBUTOR – 18-5484-1

swperformanceparts.com

“A Team Performance” Delco EST which can be found on Amazon for $200. It had good reviews so I’m not saying they’ll all be faulty but I guess you also get what you pay for. The Sierra ignition control module was $170 so I still ended up with a working distributor for ~$370 which is a few bucks less than what the whole package from Sierra would have cost and less than half the price of an OEM one from Volvo Penta. I have a ticket open with Amazon and the seller to see if they’ll do something to compensate me for the faulty module, but it was out of the 30 day return window so we’ll see.