I have a mercruiser 350 slightly modified with ported polished vortec heads, stepped up cam and IMCO powerflow through the hull on a 21 foot boat - alpha one at altitude of 5280 feet. Bought the MSD 6m with MSD distributer and MSD blaster ss coil as this was sold to me by teague as a must have....on a carburated engine - performer mani and rochestor 4bbl carb. The damn thing worked great for 2 minutes out of the box and let me stranded. Jumper wire over dist. leads causes spark from coil but weak at best but no spark going through distributor. Distributor unit with 5oo ohms resistance - ok. Cap rotor new. Grounds good. Is this a coil taht is weak?? Is this worth my time?? I cannot return this system as they do not take back electronic products. Old ignition TB V (off 5.0 liter)- not advancing past 30 degrees. Any suggestions greatly appreciated. This forum is the best quality forum I have seen in a while.

Doc

Suggestion...Put the thunderbolt back in. Modules can be changed to effect timing curve OR set max timing where you want it(say 32*) and let the idle timing end up where ever.
I've personally seen too many problems with MSDs to put them in MY boat.
They are good if you're spinning the engine 6500...7000 rpm but at 5000 or 5500 rpm for me , the disadvantages out weigh the advantages.
And say what you will the Thunderbolt ign. is reliable

Interesting... I had MSD's and except for a little condensation under one cap that caused a cross fire... no problems at all....

Should have gone with the Crane stuff and Merc dist.

Try the MSD Tech line before you "deep six" the system.
915-855-7123
Many people out there with great results using MSD.
The advantage of an MSD is the "multiple spark discharge" at low rpms.
Helps provide the engine with a good idle due to a more efficient fuel burn.
Make sure your wires are routed properly.
The original Thunderbolt is a good ignition system.

I've run an MSD system for years without trouble. (automotive and marine app's) They are quite effective at lowering the 'soot' factor at idle.

Brian

Thanks for the advice... I have contacted the help line and they cannot figure it out because they say the fact that the box is putting out a spark to ground with the jumper wire suggests that the system is ok - I have put the TB back in for now and am going to trouble shoot the MSD out of the boat with a new coil. Any other suggestions for increased HP in this 350 engine?

Thanks for all the input

I bought a brand new complete MSD setup a few years back, and it did the same thing. Turns out after sending module back that the main ground wire was not connected inside box. It would only work if the case was grounded.
If you keep running the TB-V ign. just figure out your total advance and adjust your base timing to get you to 34 deg. total.
I now run the stock merc. distributor with a Crane HI-6M module. Stock distributor does not corrode up inside like the MSD, and has hall effect pickup which is better than MSD magnetic pickup. The box has built in selectable advance curves and rev-limiter, as well as diagnostics and other functions. Check it out at: cranecams.com

BTW it looks like you're about there power wise, short of a supercharger. Might see a little improvement going to a squarebore Holley. Is your intake a spreadbore?
I do have a brand new in the box Holley 144 marine s/c kit (polished) for sale. Would take $1450 for it. New over $2200. It is complete.
A friend of mine had a vortec head 350 and we drilled and tapped the heads using intake gasket as a template and hung a B&M 144 on it. That thing made a ton of power for what it was! Probably better to just get some large chamber heads to drop your compression and sell the vortecs and intake.

It sounds like the crane system is the way to go - will the crane system improve drivability?? I probably cannot give away this MSD from most of the replies in the forum. I plan to continue the troubleshoot tomorrow with the additional step of grounding the box in case the ground wire in the box is loose - that makes more sense than anything else as this thing failed with high speed bouncing around.

doc