4.3 MerCruiser bogs down when pulling wakeboard or tube and under load

[alschappell389]

Hey Guys! New to this form but figured I would give it a try anyways! I have a 2004 Tracker Tahoe with a 4.3 MerCruiser Thunderbolt iV ignition. One of the problems I am having is that it back fires and sputters when I am cruising and it is hot. Usually I am going over 28 knots. I changed the spark plugs, the distributor cap, rotor, and tomorrow I will be changing the coil and spark plug cables. (Im hoping that finally fixes the problem) Anyways if you guys have ideas on that it would be great!

Another issue is that when I have people or pulling a wakeboard or tube out of the water it bogs down and wont accelerate. I used to be able to pull people out of the water fine! Tomorrow when I replace the coil and spark plug cables I am also going to clean the carb strainer, fuel/water seperator and clean out the flame arrestor. Is there anything i can do to the carbs while they are on there or anything else I can do to give it a try before I put the boat in the water and test it? The boat runs great out of the water and runs good with only me in it so it gets kind of hard to test it when I do not have anyone with me.

Thank you for all your help!

 

[saltydogjeff]

Check your timing. I don't know about the thunderbolt iv but it sounds like that might not be giving you full power and backfire.

Personally, don't just replace because it gets expensive. Plus, you get a bucket of extra parts.

 

[Scott Danforth]

Backfiring is bad. You are experiencing a lean sneeze. Go thru your carb

 

[alschappell389]

Ok I will check the timing, I don't actually think it is back firing.... I think it is sputtering if that makes sense?

 

[Scott Danforth]

its a lean sneeze, caused by a lack of proper fuel for proper combustion.... most likely due to dirt in the carb. There are tests in the stickies, including measureing fuel pressure and checking plugs. if so, it may be time for a carb cleaning and re-gasketing.

 

[alschappell389]

Ok thanks, Im guessing I will need to just rebuild the carb, but was going to see if I could find any causes of fuel blockage first.

 

[alschappell389]

So I checked the timing last night and with the engine off it is sitting at 0, I thought it was suppose to be at 10 degrees but the lines matched up and can tell that it hasnt moved. Also I changed the ignition coil and does it matter that when I put my finger to the top of it there is a little arc that goes from the coil to my finger. Does this matter?

 

[Rick Stephens]

I don't know of any way to check timing without a timing light and the engine running.

 

[alschappell389]

I just seen a mark on there and they lined up when the engine was off (was just wondering why they lined up perfectly) but I will have to check it while the engine is on

 

[Rick Stephens]

I just seen a mark on there and they lined up when the engine was off (was just wondering why they lined up perfectly) but I will have to check it while the engine is on

Means absolutely nothing. You need a timing light and the manual to know where and how to set the timing. Timing marks at rest are literally of no consequence.

 

[jbcurt00]

Huh???

Check your Private Messages