You have a TB IV igntion then. You could use V8-24 module or V8-HP module instead. The V8-HP would be my choice. The are also NLA, but they were on HP500's and there are some used ones out there.

The modules do not fail very often, but it does happen.

well, if they are both NLA, wouldnt i be better off going with a full MSD distributor instead of looking to replace a used part with another used part? I think i can get a new msd dist. for about 150. too bad i bought a new pickup for it this moning. I just want it to be relieable, and not be stranded this year.

How about using the D.U.I marine distributor with coil and be done with it.

Do I take it that this filter is installed between the (12VDC+) source and the amplifier battery circuit? Hmmmm interesting. And you say it prevents the amp from burning out. Reason?

this is true. the pick up in the disteruber is the main think that goes bad!!! i always have a spare on my boat. its funny my boat did the same thing i was in the bay i replace it .still did the same thing here it trun out to be the fuel pump .so i put a fuel preasure gauge in my dash :drink:

Fixx
 

I think the DUI may be to big and may interfear with the back of the blower?

The TB IV igntion is as reliable as it gets. Yours is 12 years old. I highly doubt you find and MSD out there that hasn't had issues in 12 years.

I had a coil leaking a little oil on my 525sc. I replaced it with and MSD high vibration coil. The MSD lasted less than 3 seasons. I put on an old Merc coil that I had that was about 12years old and the engine fired right up and ran fine.

Now back to your issues. I highly doubt that you have a bad ign module anyway. Most of the time when they go out, they just quit completely. They do not work intermittently. I still say you have a short in the wiring somewhere. Most of the wires back there are actually for the add on rev limiter on the 525SC. There could actually be a problem with the rev limiter as well. It cuts spark at 5350rpms. It could be getting stuck and cutting spark when its not supposed to. You could eliminate the rev limiter by getting a 454/502 mag TB IV wiring harness.

There is a flow chart in the Merc manual for checking the ignition system. I don't have a manual anymore. It is the same flow chart for all TB IV ignitions, so any manual will work.

So what exactly happens when you get the no spark condition??? When does it happen???? How have you gotten it to restart????

Also, here is a chart for all the module curves. The 525SC has the first V8-22 module and I think it is actually stamped as a V8-22S

A DUI would fit with no problem. There is plenty of room behind the blower.

griff, the first time it did it was on the way back to the landing after a full day of riding, while we were idling in a no wake zone. it just dead killed. lifted the hatch, looked around for about a minute, and it cranked right up. never gave me a problem again until the next outing. rode it about 3 hours and once again, in a no wake zone, it killed. but this time we waited there for two hours and still no fire. got it on the trailer, and the next day it cranked right up. havent put it back in the river since that last time, but on the muffs it runs great. what about what my mechanic said to do with bypassing the factory ignition amp and just wiring the msd box directly to the pickup, and setting timing at 32 degrees? do you think that is something that will work?

mrfixxall, there should be plenty of room behind the blower to run the DUI dist., and im saying that going off of not seeing the size of the DUI dist. the blower on the 525sc sits pretty close to the front of the engine.

It will work, but you may lose a little power on the top end. They are designed to run at 35* above 4250rpms. Doing that will also bypass the rev limiter.
You could also put a V6-14 module on it. It will give you about 10* of advance by 2000rpms.

You are just assuming its the ignition module. From what you have described, it could be that or several other things. Did you pull a spark plug to actually verify that there was no spark??? You really need to get the Merc ignition troubleshooting flow chart and a volt meter and then go through the chart the next it happens. The module case not having a good ground will show the exact same thing as a bad module when going through the flow chart.

Did you pull the module and mounting plate off the mounting bracket box??? Check for rust and corrosion.