Vapor Lock?

[TeamAllen]

I go along with Dodbert, replace the Distributor Cap & Rotor.

The Fuel pump is not a mechanical one. It is electric and mounted on the side of the engine. Should be port side forward and down low.

[R&T Babich]

Scratch everything I said since there's no spark. Forgot about checking that first. Agree with everyone else. If you're getting a spark out of the coil wire it's probably the cap/rotor. They can look perfect, but have a hairline internal crack. If no spark out of the coil, check the voltage at the coil. The coil may be bad (not likely) or the ignition electronic module is bad (more likely). Not much else there if the voltages look good.

The coil looks like a standard Ford coil from the '60s/'70s before they stopped using the threaded studs.

[TeamAllen]

There is a big red button either on or near the engine control module. It is like a fuse that can be pushed and reset. Mine is located on the back of the engine in a big black box. I think it is 30A?

I always see it when doing maintenance and think, if I ever had a strange problem, like you are describing, I would check there. Just an idea.

[dogbert]

There is a big red button either on or near the engine control module. It is like a fuse that can be pushed and reset. Mine is located on the back of the engine in a big black box. I think it is 30A?

I always see it when doing maintenance and think, if I ever had a strange problem, like you are describing, I would check there. Just an idea.

It's a 50A and if it's tripped, your engine won't turn over at all.

[Tige22ityper]

The 50A breaker hasn't tripped. Motor was turning over just fine. I will check voltage at the coil before heading out to pick up some parts. I just hope the local mercruiser parts counter has the parts I need in stock!

[dogbert]

Those parts they should have because they fail all the time (good news/bad news). My buddy and I were talking about getting a spare distributor cap, impeller and some other common failure items just in case.

[chpthril]

Well, there is no spark. I pulled the cap and the rotor was turning fine. I am going to replace the coil wire (it didn't look good after pulling it from the coil) and see if there is spark and go from there.

If no spark with the new coil wire, should I attempt to replace the coil itself? Or might there be something else I can do? Man this sucks! Less than 24 hours before we are supposed to head out! Anyone have a part number for the coil off the top of your head? Can I just go to the local auto parts store and get a coil or do I have to get a specific marine type coil for a Mercruiser?

Check for spark from the coil wire first. If no spark, substitute a plug wire and recheck. Still no spark, check for 12v on + side of "coil primary" and ground pulse while cranking on the - side of "coil primary"

Could be bad wire, coil, pick-up, module.

The 50A breaker hasn't tripped. Motor was turning over just fine. I will check voltage at the coil before heading out to pick up some parts. I just hope the local mercruiser parts counter has the parts I need in stock!

Just to clarify, at this point you DO NOT have spark from the cap, and DO NOT have spark from the coil? If so, that leaves us the coil, module and pick-up as our root cause (providing you have 12v at the coil)

With a 12v test light, you can check for 12v at the coil and ground pulse from the module. Clip the alligator to the coil + terminal and touch the probe to the - terminal and have a helper crank engine. The test light should pulse on and off as the module triggers the coil to fire. If you have 12v's and no flashing test light, the module or pick-up are the cause.

[dogbert]

Well, there is no spark. I pulled the cap and the rotor was turning fine. I am going to replace the coil wire (it didn't look good after pulling it from the coil) and see if there is spark and go from there.

BTW, this is the reason I'm thinking distributor cap. If your wire doesn't look good, it's probably because it's getting too much resistance from something downstream (more likely) or too much current from something upstream (less likely).

The longevity of the distributor cap on your engine is a known problem. If you have the Marine Power engine, you won't have this problem.

[Tige22ityper]

Had 12V at the coil, replaced the coil wire, still nothing. No spark either. Replaced the cap (couldnt get the rotor off!!) and replaced the coil too. Tried again, nothing..........cranks, but no dice.

That's it, I've had it.......going to go buy a Mastercraft! (no, I love my Tige WAY too much to resort to something that horrible)....I have to leave in less than 2 hours and still have to load up everything else to go. I am going to take it to my mechanic when I get back. Its probably the module or something, but I don't have a ton of experience with modules much less where its at. I will let him take care of it. It really sucks and the wife is especially irritated.........will have to board behind some older nautique ski boat this weekend.....and will not be able to go anchor and drink barley pops with some friends..............Boooo!

I guess the bright side, if there is one, is I don't have to trailer it 6 hours each way and will save on gas.

Thanks for all the help! I will have my mechanic show me what the problem is so I can DIY next time. If this was an old small block chev, it would have been running by now!

[chpthril]

Sent you a PM

[Tige22ityper]

Ok, WTF!?!!!!?

I got back home last night from camping (had to board behind a closed bow old nautique, but better than nothing) and talked to my neighbor today about giving me a quick tow over to the boat the launch by the house so I could get the boat on the trailer to take it to my mechanic tomorrow.

He told me no problem. I decided to go over the boat and just give it one more try just because.............I cranked it and it didn't fire...........so I then moved the throttle between forward, reverse, and neutral, tried again, and it fired right up!! WTF??? Took it for a quick spin around the lake, docked it, shut it off, then tried to fire it again, and it fired just fine!

So now what??? Neutral safety switch? Loose connection somewhere? If its the neutral safety switch, how do I check it, or replace myself?

I am real happy it started and ran great, but don't want this to happen again. But not sure where the safety switch is? under the dash? behind the throttle somewhere?

Again, thanks for all the responses! All your input is much appreciated!
Tony

[R&T Babich]

The neutral safety switch is on the side of the trans if it's a Velvet Drive like in our boat. Our boat will not crank if the switch is not in neutral so I don't think it's your problem. In an emergency/test case one could unscrew a terminal and connect it to the other to bypass the switch, but then it will start in gear. Here's some info on the trans: http://mysite.verizon.net/vze6mxo8/d...erv_Manual.pdf

I thought at one point there was an ignition module on the Mag MPI engine, but I think the "module" is part of the ECM - Engine Control Module. Unless it's under the cap - I haven't had that off, yet. There's no listing of a seperate module on the Merc Parts Express parts list for our engine. The ECM is discontinued and I haven't found another source for it.

There are 2 relays on top of the engine (left side of engine, right of boat). At least one is triggered by the ignition switch and it supplies power to the starter solenoid and the ECM. I don't think the ignition switch goes directly to the starter solenoid. I can't get to the Merc Parts Express wiring harness diagram (site gives no response) to tell what wires, but maybe the ECM is not getting power (faulty relay contact) even though the starter solenoid is.

[R&T Babich]

Got to the wiring harness diagram and it's not the relays. One the relays controls all the power: coil,ECM,injectors,fuel pump. The 2nd relay is for the fuel pump and appears to be activated by the 1st one. There is a 3rd relay, a larger starter relay, that gets power from the ignition switch that controls power to the starter solenoid.

It really seems like an intermittent electrical issue - connectors, sensor, ECM. The easiest to try first would be reseating all the connectors and using electrical contact spray on the pins in case there's corrosion. I don't think moving the throttle/shifter directly would be the problem. The only electrical circuits connected to those linkages are the TAPS switch in the throttle handle, the throttle position sensor on the throttle body and the Neutral Safety switch on the side of the trans. Take a close look at the throttle position sensor connector. Are any harness cables rubbing the throttle/shift cables that would be moved when the cables flex?