2000 Bayliner Misfire?

[Bodyshot]

Hello all I have a 2000 Bayliner 2855 with a miss that has steadily gotten worse. Fresh water boat only second year of ownership. The boat ran great for about 3 weekends last year then I noticed a very slight surge in no wake areas. This has gotten worse now to the point where getting the boat to cruising speed in not really possible so I don't try.

Engine S/N 0L691360
New parts with ~30 hours on them are Cap, Rotor, Plugs, wires, Ignition coil, water pump, fuel water filter, and plenum gasket.

No codes on the MEFI 3 diagnostic port. Pulled the injectors after warming them up and checked Ohms, all were at about 12ohms. (I hear bad things about the old Delphi injectors so I started there) Cleaned the inlet filters and no change. Pulled one plug off the cap at a time (possibly need a pacemaker now) but a very slight change when each plug was pulled at idle. Gas tank looks pretty clean but I need good scope to make sure.

Pulling the plugs soon and checking timing and fuel pressure.

Any help would be great

 

[Bodyshot]

After reading the Adults only section I'm going to go through the fuel system for possible air intrusion. I did see some bubbles when bleeding the rail after re-installing the injectors.

 

[QBhoy]

Hi. I’d start simple and prove it’s not the fuel that’s causing this. Dip the fuel supply pipe into a Jerry can of known fresh fuel and see how she runs. As in, bypassing and ruling out the fuel tank and supply as being the cause.

 

[Bondo]

New parts with ~30 hours on them are Cap, Rotor, Plugs, wires, Ignition coil, water pump, fuel water filter, and plenum gasket.

Ayuh,..... Welcome Aboard,...... Pull the fuel filter, 'n dump it into a clear container,....
Yer lookin' for anything, but clean fresh gasoline,....

Put a new filter on it, 'n hook up a remote fuel can of fresh clean gas, directly to the filter, 'n try it,....

 

[Bodyshot]

Hi. I’d start simple and prove it’s not the fuel that’s causing this. Dip the fuel supply pipe into a Jerry can of known fresh fuel and see how she runs. As in, bypassing and ruling out the fuel tank and supply as being the cause.

I'm almost done re-doping and tightening all the fuel fittings and have a new tank pick up tube and Fuel/water filter ready for when I try your suggestion. I'm going to pull the pick up tube and replace it then cap the tank and slip the tube into a gas can cap. Hoping its not the tank or I'm out ~$500 in gas to empty and clean but we will see.

Boat has about 410 hours on it, replaced the coupler and rebuilt the transom when I bought it and at that time (before last season) it had 384 hours.

 

[Bodyshot]

Ayuh,..... Welcome Aboard,...... Pull the fuel filter, 'n dump it into a clear container,....
Yer lookin' for anything, but clean fresh gasoline,....

Put a new filter on it, 'n hook up a remote fuel can of fresh clean gas, directly to the filter, 'n try it,....

I'm trying this tonight.

Thank you!

 

[QBhoy]

I'm almost done re-doping and tightening all the fuel fittings and have a new tank pick up tube and Fuel/water filter ready for when I try your suggestion. I'm going to pull the pick up tube and replace it then cap the tank and slip the tube into a gas can cap. Hoping its not the tank or I'm out ~$500 in gas to empty and clean but we will see.

Boat has about 410 hours on it, replaced the coupler and rebuilt the transom when I bought it and at that time (before last season) it had 384 hours.

Good stuff. Years ago I was on a bayliner 2855 with a 5.7 carb. Was in rough weather, it started running terribly and cut out. I ended up taking the pick up pipe out the tank for a look. The bottom of it had gunk trying to clog up. So did the non return check valve in the line too. I temporarily raised the pick up pipe an inch higher off the bottom of the tank and got us going again to the marina.

 

[Bodyshot]

Ok so after resealing every fitting and replacing the fuel filter (with the exemption of the pump connections). I took fuel pressure readings. Initial pressure before ignition was 38. That bled down to about 30 after 15 minutes.

Idle pressure is right around 31 and with quick throttle blips spikes to 37. Slower throttle increase drops below 30.

Thats too low. I have a Titan pump and regulator on order. It’s NOT going to be a fun job replacing these as it smashed under the manifold and engine mount.

 

[dubs283]

Your issue is fuel related, good troubleshooting info provided I would focus more on fuel delivery prior to the pump.

Replacing the fuel pump and fittings/line is apprapo but looking, getting eyes on the tank is good too. A vacuum test works wonders under load

 

[tpenfield]

You mention surging at idle speeds and a misfiring, and now the boat does not want to get up on plane. So, is it surging, misfiring, or both?

You said you checked for codes. Does that mean you have a scanner? If so, you may want to check the TPS readings while idling and even getting on plane. See if the TPS is giving you the expected readings, based on the true throttle position.

 

[Bodyshot]

You mention surging at idle speeds and a misfiring, and now the boat does not want to get up on plane. So, is it surging, misfiring, or both?

You said you checked for codes. Does that mean you have a scanner? If so, you may want to check the TPS readings while idling and even getting on plane. See if the TPS is giving you the expected readings, based on the true throttle position.

It started out as a slight surge feeling in no wake. But the RPM was just dropping out so it was likely a very slight misfire. But the boat would cruse without hesitation. Now, however, the misfire keeps the boat from planning out generally. I can get it to plain for a bit then the issue starts and she drops out of plain. I’m not even trying anymore because I’d rather not hurt it. So we just get to where we are going under 2000 rpm. At that rpm the miss is nearly unnoticeable but I think it’s still happening because I can feel it with my hand on the motor at idle every so often

 

[Bodyshot]

Your issue is fuel related, good troubleshooting info provided I would focus more on fuel delivery prior to the pump.

Replacing the fuel pump and fittings/line is apprapo but looking, getting eyes on the tank is good too. A vacuum test works wonders under load

I’ve used this fuel pressure guage for 15 years and I’ve never seen it bounce around like it did when testing the boat. I’m going to make a YouTube video of the guage and I’ll post it up so you guys can see what I mean. It was bouncing at idle and still even a bit when I rev the engine. Didn’t pull the vacuum line on the regulator to see if the pressure spiked though.

 

[Bodyshot]

One more thing and this has to be said.

Thank You all for your help. Without the experience of people like you the DIY community would be half what it is. You make it possible for many to enjoy this recreation that normally would not be able to afford it.

Thank you!

 

[Bodyshot]

Wow! This fuel pump is no walk in the park. Had to cut the cover off because it was smashed between the pump and the motor bracket. Accidentally cut my cooler hose in the process. What a joke. There was absolutely zero reason to put the pump here, it an inline pump. It could have gone anywhere. On a twin setup the engine would have to come out. Insane…

 

[Bodyshot]

So the Titan pump came and the hole for the outlet fitting is not milled centrically to the housing. This is either going to cause the fuel to spray out of the o ring fitted 90 going to the cooler or its at least going to reduce efficiency. What I get for not spending $900 plus on the merc pump and cooler kit.

What do you guys think about getting a Walbro 255 LPH inline pump to fit the bill. I have no reason to think it will not work other than fitment issues.