Timing Issue *Fixed*
 

I'm having a difficult time getting a timing issue fixed on my '98 Mariah with a 350 Mag M.P.I. engine. It started last summer, I noticed when I was cruising the engine would slightly surge, dropping a couple hundred rpm intermittently. After I was aware of it I noticed that sometimes the boat would run fine and other times it would feel like it was missing hard. So I took it to my local MerCruiser dealer. I just got the boat back after 6 months when he gave up. On his dyno he found that the engine timing is abruptly changing. When he ran the boat in a diagnostic mode eliminating the ECU timing the boat's timing is stable. So he replaced the coil to distributor resistor wire, ignition module, cap/rotor/plugs, new coil and lastly the ECU. All having 0 effect on the problem. He also found that the boat had to be warm before it would exhibit the problem, so it is temp. related.

He thinks the problem could be in the main wiring harness. He believes when he pushes the connector aft that the problem goes away. He's unplugged the harness and cleaned it/inspected it, but see no visible issues with it. I thought it best at this time to move on to someone else, and get a fresh pair of eyes on it. I was hoping, praying, wishing someone on the forum had an idea.

Re: Timing Issue
 

tdmaker,
Did your mechanic fully check out the Knock sensors, Knock module and the wiring from these sensors and module to the ECM? That's where I would start. When the ECM senses that knock is ocurring, it retards the timing. Good luck.
Steve

Re: Timing Issue
 

Well, I'd have a hard time thinking that the dealer didn't call Mercruiser about your issues. Did he? Did he look to see ALL the service bulletins specific to this engine. You should either call/e-mail the factory and ask them to go over them. Why pay someone else to repeat the same "mistakes" the 1st dealer did. AND, someone should do a compression check and cylinder leak down check. The factory almost won't talk to you unless it's done!!

Re: Timing Issue
 

Well I finally got my timing issue solved. I met up with an old friend at a funeral who gave me a number of mechanic in St. Charles, Mo. After telling him everything that I had changed, he quickly zeroed in on the distributor. I was very skeptical that changing the distributor would fix it, but I figured at this point what did I have to loose. I took it out today day and sure as heck it fixed it. Even before the timing issue I'd say the boat ran ok since I've owned it, but I wouldn't say great. The exhaust always smelled like it was running really rich, and when I would pull the throttle to neutral really quick it would die. It seems it was all related, today was the best it has ever run for me. The only downside to the new mechanic was that I drug the side of my truck down a trailer tongue of another Mariah he had parked there to do an engine swap on. It just had to be a Mariah! I guess you win some, lose some. :wink_thumbup:

Re: Timing Issue *Fixed*
 

Td, I live in o'fallon mo and mostly go out on the Mississippi. What about you?

Re: Timing Issue *Fixed*
 

Sorry for the slow response Finleydj. I'm not on the forum as much as I should be. I'm from Belleville, over in Illinois. So we spend a good amount of our time on Carlyle lake, but occasionally will go on the Kaskaskia river and sneak through the lock and dam onto the Mississippi.