TomZ

iTrader: (2)

TB-IV modules don't really fail this way. They generally just die unless there's corrosion problem causing a jump across terminals in the boot (that's what happened with my V6 module). I have seen the system drop random cylinders, but only on a TB-V (a system that's prone to problems... Merc's fix is to replace with a TB-IV or aftermarket). TB-IV's are stupid reliable.

You have cylinders dropping off under 1k rpm. Are they the same cylinders or is it random? Have you changed plugs? Could any be fuel fouled? What about water intrusion? Any exhaust issues that could be drowning out cylinders at low rpm? What camshaft is in the engine?

Sorry... grasping at straws to help you out here.

Redneckcustoms13

Batteries brand new. Load test with 350 amps bounce back to 12.4v. Alt charging around 13.8

Redneckcustoms13

Tom to answer your questions. Yes sir the plugs are new. It sounds like 2 or 3 cylinders are picking up and dropping sporadically as it is at idle up to around 950-1000 once above that you can't really hear or feel any vibration. The exhaust seems tight no signs or exhaust leaks. The cam shaft is a stock 450hp 454. I will check the modules in the parts boat this evening. It is very possible this one died when water was spraying on it due to the lack of speedometer fitting.

Thank you guys again for all of your help!

ph1971

iTrader: (1)

Watch the exhaust at the stern while idling. If its sputtering on one side only, could be a riser gasket.

Redneckcustoms13

It feels like both sides if you put your hands on the risers. It's odd. Almost feels like when a plug wire is breaking down.

DBleil89

I might have missed this so I'll ask, what generation is this block?
If it's a roller cam in a general 6 block you may have an issue with the distributor gear. I put my thunderbolt distributor in my gen 6 and found it was wearing out my distributor gear. The roller cam gear is hardened so it tears up the stock gear on the distributor. I had to buy the composite gear to run on the distributor to prevent metal shavings in the oil. This most likely isn't your problem, but I know my brother in law and I messed either the tb vi for days and swore it was a module when really it was the gear was missing a tooth.

Redneckcustoms13

This is a normal flat tappet cam shaft in a gen iv block. Just has roller rockers. Good suggestion though.

TomZ

iTrader: (2)

What's a "stock 450 HP" cam? Do you mean the factory Merc 365 (454 Magnum Cam)?

The reason I ask... if the cam has too much overlap, it will start sucking water into to the cylinders. That's why I was asking about the exhaust too. If you have some exhaust mist coming through, you could be knocking out cylinders that way. Just a suggestion.

Do you have the cam card handy? I'm curious as to what's in there.

79formula

Merc did make a 450hp. It was a carbed merc hp500 except 454 cubes.

Redneckcustoms13

The man that built the engine is going to look in his file cabinet tomorrow and get me the cam card.

Today afyee work (5:30 almost dark) my work partner towed one trailer while I pulled the other and we swapped it onto the other trailer.