I have a sick 1970 Donzi Ski Sporter

[Bobby D]

Problem Statement:
I am having trouble finding anyone who is comfortable working the problem due to the age and the fact that it is an old 351 Ford Holman Moody Volvo setup. My problem is the boat ran perfectly last season and than I winterized it and put it away for the winter. This spring (April) I got the boat out of storage and took it home to clean it up and de-winterize. The boat started up as always sounded great and ran perfect for about 4 to 5 minutes and than quit just like I turned the key to the off position. After letting it sit for about 2 or 3 minutes the boat would start back up and run again for about 4 to 5 minutes and than quit. My judgment was I had some type of electrical problem with the MSD ignition system (red box) and I know that MSD now makes a marine (blue box) and distributor. The system was over three years old and it was time to look over the engine in general because it was definitely running rich and things may need replacement and or adjustments.
What did I do about it?
Installed a Ford distributor set up for a 351 Ford Windsor and new spark plugs. Went over the entire fuel delivery system and made sure everything was okay there. The main filter was a couple years old and I replaced it as well. After the work was done I took the boat out for about 2 hours and it ran great. Boat started up as usual without the four-minute shutdown and all systems checked out OK including all the gauges.
Now what?
I am sad to report that after three additional flawless trips out on the Susquehanna River the problem is back again. Last night on the way back to the marina the engine shut down the same way again just as if I turned the engine off with the key. What was different this time is the engine would not start back up, all it did was crank. We were out for about three hours and had made several runs up and down the river and had shut down the engine four or five times at several locations to go swimming and grab a bite to eat.
What I think I know:
The problem appears to be electrical based on the way it just shuts down. The fuel pressure gauge reads 5 poundsand before I went out I filled the boat up with gas so we can rule out fuel delivery. If it is electrical and the distributor, plugs, and electronic ignition are new than it must be something else. Any suggestions on what to go after next will be greatly appreciated.
Regards,
Bobby D

[MOP]

Lots of could be's! Ignition switch can do that, corroded ground especially ones on the cylinder heads as they work while damp and die when the engine gets temp and dries them out. You can connect a volt meter to the purple wire on the key switch and to ground watch to see if the power cuts when it dies, that will rule the switch in or out of the picture. Look for the big black ground in the main engine harness its ground is essential, several more ideas will pop up from some of the other guys!

Good Luck!

Phil

[gold-n-rod]

I know the drivetrain in my big boat (see below) is completely different from yours, but I experienced a similar problem about 10 years ago when it was almost new. It stumped everyone who looked at it.

I decided to look around for loose wires and as I was doing so, knocked a small nut off the back of the distributor. It had been holding a black wire that I traced back to the ignition module. The problem was intermitent, but the loss of the nut would have made it steady.

The moral of my story is that you should run down every single connection to be sure that grounds are good. With the age of your boat, something like that could easily be the culprit.

Good luck and keep us posted.

[WA-LO]

I would also check the fuel tank for trash, somtime you get deris or water in
the tank and it will move over the fuel pickup. if you dont have one get a fuel filter water seperator.

[BigGrizzly]

Two things If your fuel pickup has a screen on it it will pick uptrash and let it go when the engine stops. I chased this for two weeks. I removed the screen and put on a real filter. the other thing on my 16 was the original teleflex tach would get an intermittent short. I jumped from the battery to the resister and discovered this. Good luck

[vonkamp]

Like Wa-Lo said, I would look at fuel tank trash as a possibility. The same thing happened to me even with a water seperator. I had at least a gallon of water and about an inch of sludge on the bottom of my tank.

[downtime270]

I know from experience Merc's are synonymous with this type of failure. The cause is the big round engine plug that connects pretty much everything together. A slight giggle with a not so great connection and boats will die. Not sure about the ford wiring - but definitely sounds like electrical / wiring / connectors. If you have a battery switch don't forget to check there as well. Not sure if your familiar with it but I am a big proponent of Boeshield T9. If your taking the time to go through your connection - might be a good opportunity to clean them up and protect them. The coating is great - and can be used as a thin protectant or applied in multiple coats for a thicker build.

-e-

[BUIZILLA]

is the coil getting overly hot when it does this??

[Sweet little 16]

check your gas tank vent line for a blockage

[slamdry]

check and see if you have lost spark or have week spark. The color of the spark should be a nice purpley blue when it arcs to ground.

i had the same problem over the weekend and have found my new coil pooped the bed.

[Bobby D]

Thanks to everyone for your quick response and excellent suggestions. The electric company has me working long hours this week however the plan is to get started and figure this thing out Sunday.
I will keep you posted
Bobby

[Bobby D]

Update on how I made out this weekend:
Performed trouble-shooting plan to figure out what the problem was:
1) Checked the ignition switch to the coil and performed a positive and negative test for voltage. Meter read 12 volts at the coil.
2) Went under the dash and checked all the connections, cleaned and tightened the power to the battery contacts at the ignition switch and performed continuity check and functional test for 12 volts, all were found to be good.
3) Checked wiring for the ignition switch to the coil and found 12 volts thru the switch.
Found the Problem:
Performed a spark check using the center coil wire from the distributor and a wire off the cylinder to ground and found no spark.
Why did the no spark problem happen again?
I have a copy of the 1972 Holman Moody owners manual for 302/351 Ford engines and after reviewing the wiring diagram I found that I do not have an ignition resistor to limit the current and I smoked the Pertronix ignition module
What I did about it:
I ordered and installed a new PNX-1281 igniter module and a new ballast resistor.
I checked all the wiring again and the engine started right up as usual with no problems. Let it run for about 30 minutes and shut it down and looked everything over again and found no problems. Started up and shut down several times during the day and all checked systems checked out OK. We went out on the river Saturday night and had a nice evening run and are looking forward to enjoying the rest of the summer season.
It should be noted that the first module I installed did not come with installation instructions, however the second igniter module came with an instruction sheet that included information that eight cylinder engines require a minimum of 1.5 ohms of resistance and a wiring diagram for the igniter system installed with a ballast resistor.
Thank to all for your recommendations and I hope this information can benefit others with a similar setup.
Bobby D