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Discussion Starter #1
Ok, here is the deal. I have a buddy that has a 32' offshore performance boat. The boat has twin 14-71 blown 582 BBC engines. The engines are pump gas engines and make about 950hp each (mind you all day long). He is having some ignition box problems. What are some of you guys running for ignitions? I know we have some offshore performance guys on here. Are you guys running automotive boxes or marine boxes? How long are they lasting? Any help is appreciated.
Thanks,
Mike
PS: This is a SALTWATER application.
 

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42 foot Apache w/ two 598" Big Block Chevys. A pair of MSD 7531 boxes lasted about twenty minutes before engine number one shut off. The 7531 would have been great for slew rate limits while boat comes out of water, but apparently these are not good for endurance applications. The boxes have been since switched out to a pair of good old fashioned analog 7al2+. Has been good for one season so far. So much for a cool rev limiting function.
Engines run @ 6500 RPM for close to 45 minutes straight. MSD may recommend their HVC box for your application, but I don't know that they will have the poop for the blower deal.
 

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A 6a box will last about 6 months at best. I run the marine version of a 7al, think its a 7m or something. Been running 3 years no problems at 1400 hp blown 600 ci engines
 

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Discussion Starter #6
42 foot Apache w/ two 598" Big Block Chevys. A pair of MSD 7531 boxes lasted about twenty minutes before engine number one shut off. The 7531 would have been great for slew rate limits while boat comes out of water, but apparently these are not good for endurance applications. The boxes have been since switched out to a pair of good old fashioned analog 7al2+. Has been good for one season so far. So much for a cool rev limiting function.
Engines run @ 6500 RPM for close to 45 minutes straight. MSD may recommend their HVC box for your application, but I don't know that they will have the poop for the blower deal.
Very interesting with the 7531. Did MSD say why it the box died? Too much shock and abuse from the waves/surf? I appreciate the info!
Thanks,
Mike
 

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Discussion Starter #7
A 6a box will last about 6 months at best. I run the marine version of a 7al, think its a 7m or something. Been running 3 years no problems at 1400 hp blown 600 ci engines
Shawn,
Thanks for the information. That is interesting about the 6a box. That is what he was talking about. I realize the 6a is the wrong box for the water though. Thanks for the link below as well. I appreciate it. Have any pics of the boat/engines?
Thanks,
Mike
 

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6-M with the soft touch box with 2 600" blown 1100 hp . All I have ever used besides the Mercury thunderbolt ign w/ the V-6 box.
I mount 3 ) 6-M's side by side on a plate usually mounted on the front bulkhead. The center box can be plugged into either the port or starboard harness in case of box failure while out in the water.
The 6-M is not repairable as it is encased in epoxy inside. Have tried the 6-M-2 box on a single app but it only lasted 6 months.
6al get used because it is cheaper than a 6m but again it is not encased in epoxy so it's life will be short.
 

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Shawn,
Thanks for the information. That is interesting about the 6a box. That is what he was talking about. I realize the 6a is the wrong box for the water though. Thanks for the link below as well. I appreciate it. Have any pics of the boat/engines?
Thanks,
Mike
send me your e mail, too dumb to post em
 

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Salt.
Salt in Fla.
Salt in the USVI.
No, only 6-M is potted along with the soft touch for the 6-M.
 

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Supposedly, the 7531 box is not good for endurance applications. High RPM over a relative long period of time (20 minutes I guess) overheats the box and burns it out. This is contrary to what one of the tech guys told me at MSD when the boxes were originally purchased. Bad info, no big deal. They did fix the box for nothing (kudos to them for that at least) but told me to stop using for this application. This is a salt water application, but I doubt that 20 minutes of salt water exposure would send the electronics to circuit board heaven.
 

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Mercury Thunder Bolt That Comes On The 900SC Is The Best Marine Ignition Out There Expensive But Worth It,,I Believe Its Still Available In There Parts Book
 

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Mercury Thunder Bolt That Comes On The 900SC Is The Best Marine Ignition Out There Expensive But Worth It,,I Believe Its Still Available In There Parts Book

I've replaced more Merc Thunderbolt ignitions off those 900 S/C's than I want to think about. If you want to stay with the mercury setup, the only box that works and LASTS, are the ones that came on the early Merc 1000's. I replaced the factory 900 S/C boxes with the early merc 1000 ign boxes and NEVER had a problem yet, and it's been going on 3 years, and on several different boats.

I've been running the MSD 6M-2 boxes with the soft touch rev control on my engines going on my 10th season, installed them in 01. Same boxes, no problems. Now watch, now that I say I hav'nt had a problem, when I go to start the engines in the spring, a box will take a shit on me. LMFAO

I like that idea of having the 3rd box in the event that one goes bad. I've got plenty of friends that have these boxes go bad almost once a season. Maybe it's because mine are so old ??? Did they make them any better back then ??? I'm almost afraid to switch them with all the problems that I've been hearing and seeing out on the water. My engines are only 580cu. in. hyd roller, & 950 hp @ 5900.
 
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