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Problem with 225 Pro Max

nickhedstrom

nickhedstrom

Member
96 225 Pro Max, I had the boat out several times this year prop testing and it was running fine, 6200 RPM at 74 mph, I had a mechanic stop by and i showed him my left side voltage regulator and he said it was bad which is why I had low volts at low rpm, so i changed it out and my volt were up. So last saturday i had the boat out and it was running perfect all day, the next day i took it out i could barely get 4500 rpm. So i changed plugs to diffent type BR8HS, and it still ran rough at idle in driveway, cleaned all plugs to look like new and reinstalled and ran at idle for 5 min and removed and 4,6, and 1 plugs looked very clean and 2,3 and 5 were black like they been firing and the others not. I did find a weak coil on 3 and replaced it but still a problem. Took it today to a Mercury dealer and they did a spark test and it came out good. They did a leak down and found 1,3 were at 10%. Pulled the head and the gasket was not blown but very little scoring. Dont think thats the problem for the way its running. When i was running it in the driveway for little time the prop turned very black. Anybody got any ideas of which way to go next or have had simaler experence like this? Thanks
 
You can use the mercuryshop manual or the CDI troubleshooting guide to test your switch boxes and stator. Given your symptoms I'd be looking at one of the switch boxes first and given that the motor is still running I'd look at the one NOT firing the injectors. If it does test bad you'll want to replace both.
 
If you have a 225 Pro Max you are going to have to learn how to speak Mercury. I dont know that their is any other name for them. They are the switch boxes. They are Capacitive Discharge ignition controllers. They step voltage up from the stator and fire off the triggers signal to power the coils. Outer bank fires 2,4,6 and inner bank fires 1,3,5. and the fuel injection ECU.

Send me your email and I'll send you a drop box link to a Mercury shop manual on PDF.

mikeprewitt@gmail.com
 
O ur talking bout the 2 power packs, 1 runs 1,3,5 coils and the other runs 2,4,6 coils. They did a spark test and said coils, power packs, and flywheel output good. Do u think a simple spark test can tell u all those components r good?
 
Yes the coil side of the stator. There is a high and low speed coil for the ignition side. I had to build a adaptor to use my mutitool to find it.
 
You can buy a DVA adapter for testing for $25 or so.

Power Pack is the OMC term.

Switch Box is the Mercury term.

Dont be an OMC guy with a Mercury..

High speed side of the stator is going to cut out over 2500 or so its bad. The battery has nothing to do with the ignition circuit. If you are cutting out over 4500 I'd be looking more at fuel delivery.
 
Mine would work for a bit until it warmed up also. Stone cold it would run good then start dropping voltage to the coils after it warmed up
 
You are going to have to do some testing unless you want to start changing parts willy nilly. You need a DVA adapter and a fuel pressure gauge. I think you might be dropping fuel pressure at speed either from a poor regulator or a fuel pump/filter. You can tell a lot with a cheap ful pressure guage , a schraeder valve adapter and long tube. Given that you are dropping at higher RPM than the high speed coil would normally be responsible for I don't think you are looking for an ignition problem but you really need a DVA adapter to be sure.
 
Do some testing then let us know where you bought a stator from. You can find out how to build a dva adaptor for a few bucks and the testing procedure and values on scream and fly.
 
Well, after you buy a stator and figure out you have a new stator for $350 and it still runs the same email me at mikeprewitt@gmail.com and I will send you a PDF copy of the Mercury shop manual for V6 Mercury motors. It has all the troubleshooting steps you need to actually figure out what is wrong with it before you start buying parts.

Or I could send it to you before you start wasting money. Your call.
 
Part of the test process that Wired is referring to addresses the voltage regulator. In my mind ( a scary place ), a bad voltage regulator can cause ignition irregularities. From your original post, it sounds like changing the voltage regulator is what started the problem. Remember too that the alternator driven charging and ignition system does not charge like a car does, although some later motors do have a separate alternator driven by a belt from the engine flywheel. Does your installation use the separate alternator? Depending on the charge/condition of the battery, it might appear to have low volts ( maybe 12.8 ) after cranking and initial fire up, and might slowly build to, say, 13.5 after a short period of time while idling in the driveway.
 
Jimway said:
Part of the test process that Wired is referring to addresses the voltage regulator. In my mind ( a scary place ), a bad voltage regulator can cause ignition irregularities. From your original post, it sounds like changing the voltage regulator is what started the problem. Remember too that the alternator driven charging and ignition system does not charge like a car does, although some later motors do have a separate alternator driven by a belt from the engine flywheel. Does your installation use the separate alternator? Depending on the charge/condition of the battery, it might appear to have low volts ( maybe 12.8 ) after cranking and initial fire up, and might slowly build to, say, 13.5 after a short period of time while idling in the driveway.
Click to expand...


Yes, Low or high voltage will cause the ECM to lock up. Neither charging or battery voltage affect the ignition system but high or low on either can affect fuel pump operation, pressure and ECM function.

If you just want to test the stators high speed coils let it warm up on the hose and attach a timing light to #1. Disconnect the throttle at the fuel management bell crank and the throttle cable. Pull in the advance lever . You should be able to get it to rev up to 4000 or so without opening the throttle plates or engaging the lower unit. Watch the pretty flashing light. If it stops flashing over 2500 or gets wonky then its your high speed stator coil for that bank. Then do the same thing for #2 to check the other coil. If its firing fine and revs up fine I'd start looking at fuel supply. It takes almost no fuel to rev up on the muffs but in the water in gear you need a LOT more fuel and a clogged filter, crappy regulator, stuck VST float or either of the fuel pumps or a kinked line will go BWAAAAAHHHH and fall on its face if you give it too much throttle and then pick right up like nothing was wrong if you back off on the throttle.
 
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So I'm guessing that the Pro Max is the single air opening fuel injected rig without the air pump and fancy ECU but with a nylon oil pump drive. When I saw the model year, I was envisioning three two barrel carbs. Sigh.
 
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