1999 5.7 2bl timing issue

[BayBoy]

I have a 1999 3200SCR with twin 5.7 2bl (250 hp) Mercruisers. I had never touched the ignition timing however when I checked it this spring it wasn't even close to 10 deg BTDC as specified for these engines. When I chaged the timing to the correct setting (I did lock the engine into base timing mode and set the idle at 650 as specified) the engines began to run rough and when I shut them off after being warmed up the dieseled for several seconds before finally stopping. I have also had issues with the fuel/air screw not having any effect. I have pulled out the fuel/air screw and flushed the passage with carb cleaner and it seemed to help and I have backed the timing off to, I am guessing, 8 deg BTDC (hard to tell since there is only one mark on the indicator).

Is there something I am doing wrong or overlooking? I have new plugs, wires and cap on both engines.

[seapuppy]

sounds like you may have a carb problem....try getting it rebuilt and see if that helps....a 1999 carb is probably due for a rebuild...


SP..

[BayBoy]

I had though about that and have even located the rebuild kits however I contacted Marinemax after my original post and what they have found is that the 1999 +/- engines were designed around straight gas and now with ethanol in the mix, the change in flash point requires moving the timing to about 7 or 8 deg. BTDC in order to get the same burn. So I was close by moving it where I did however I need a digital timing light to get it dialed in perfectly. Also, the fuel/air screw will need some tweaking in order to get the mix correct with the ethanol.

I will post the results after I make the changes in case anyone else is experienceing the same issue.

[BayBoy]

Problem solved. I calculated 3 degrees of rotation based on diameter of harmonic balancer + 2 x the distance from the surface of the balancer to the indicator plate. Made my own degree tape with 7 degree BTDC and 10 degree BTDC markings and overlayed on original indicator. Set the timing @ 7 degrees BTDC and idle/air screw at 1 3/4 turns instead of 1 1/4 per manual. Engines now run like tops! Actually an easy fix once I understood the issue.

[seapuppy]

great news...how bout posting a new thread explaining what problem you had and what you did to correct it...might help someone else later with this exact problem...


SP

[BayBoy]

Posted a new thread per your advise. Hope it helps someone else with a similar issue.

[seapuppy]

great..I added a sticky so it will be there till the end of time!!...


SP