Runs Perfect for 45 Minutes

After about 45 minutes running, my 1973 Nautique with a 351 sputters and then dies and will not start back up. This happens every time the boat goes out. I believe this has been a problem for years, however, I haven't noticed it much, since it is usually run for about half an hour at a time. The fuel pump recently quit working and I had it replaced. I was hoping the new fuel pump would solve the problem. When it breaks down, I usually get it back to shore. After about a half an hour, it starts back up and runs normal again. It would be greatly appreciated if someone could direct me on how to troubleshoot.

definitely check the anti-siphon valve on top of the fuel tank, take apart and clean

eric lavine wrote: definitely check the anti-siphon valve on top of the fuel tank, take apart and clean

I guess that this is your issue. My 78 did pretty much what you describe and it's anti siphon valve was full of crap.

For me the problem got progressively worse every year I had it until I cleaned the valve out. At that point I had already swapped heads, intake and all that assuming my issue was a gasket leak or some other issue.

I tried a new fuel pump and that didn't correct the issue either. If it can't get gas to it, it won't matter if the pump is good.

mma3447 wrote: I will definitely check the anti siphon valve. Thanks.

after you find out this isn't the issue and the problem occurs again, put you hand on the coil and tell me how hot it feels, try not to get burned. Then I explain to you your problem.

I'm voting on the coil as well, had a similar problem 3 years ago with another boat. We would run down to pick up a friend, and once he got in the boat like clock work it would start running poorly, turned out to be a bad coil.

New coil, but I'm sure there will be some further explanation as to why and I curious as well.

Well, definitely don't get an Accel brand coil. Those are junk. I had one in my martinique and it totally crapped out after about a year or so.

This really does sound liek a coil issue, especially if it runs fine all through the rev rang until it stops running.

Try pullinga plug wire and put a spare or known good plug on that wire and cround it to the block. if it still sparks after the boat won't re start, then it's not in your ignition.


I just mounted my MSD coil vertically because the original coil bracket that held it horizontally broke. I was able to bend the old bracket straight and use a hose clamp to secure it pretty much straight up and down.

79, would an Accel 8140 coil work fine without the resistor on a Prestolite convertion?

The spec for the 8140 are:
Primary resistance: 1.4 ohms.
Secondary resistance: 9.2 k ohms.
Maximum voltage: 42 k volts.

Picture that instructions are confusing for many of you, how they are confusing for us foreigners.

I get a tach miss from time to time since the convertion. I feel something in the electrical system is not right. Also coil started leaking.

79nautique wrote: mount the coil vertically and don't have it laying on it's side.

HHHHMMMMM Why and who would have ever predicted the coil was the issue.

Most coils are oil filled, lay them on there side the windings get exposed internally, that section gets hot expands, contracts expands contracts and then it breaks.

Get a epoxy filled coil no issues. If you shake your coil and hear fluid moving you need to mount it vertically.

If you have to mount it horizontally then the tower end should be tilted up as much as possible so the air pocket internally is not exposing the windings internally and the coils life will be much longer if you do.

I am a little lost with this tech talk about coils. So, correct me if I am wrong. If it is determined that the coil is my problem, which can be confirmed by the spark plug wire test described earlier, the easiest fix would be to replace with a gel or epoxy filled coil that can handle higher heat. I am guessing that the thicker viscosity will also keep the windings covered when the coil is installed horizontally. This sounds easier than replacing with an oil filled coil and figuring out a way to mount vertically. Am I on the right track? If so, it sounds like an Accel 8140 coil could work for my 73'. However, how can I determine which coils will work? Which would be the best coil to use for this application?   

OK. Thanks.

My setup has an Accel 8140 with no ballast resistor also. The fella I bought it from did not connect the purple wire from the voltage regulator to anything. Is this correct?

Mike wrote:    How can I determine if the breakerless conversion is "bad"?

Ground the (-) coil wire & then see if the coil produces a spark when you unground it. That's all the points or breakerless circuits do.