351 engine miss

sounds like 2 plug wires crossed. Could happen during winterization. Check your firing order.

skibums wrote: Thanks SNobessed. Wasn't the plugs. Bought a new set this morning and double checked the wires. It actually seems worse with the new plugs. It will hardly stay running. I'm running out of ideas and parts to throw at it.

Plug gap? firing order confirmed? Dwell and timing confirmed? Point set or converted to one of the Electronic?

I'm sure someone here will quickly tell you the firing order, but it also should be stamped on the block somewhere.

You really need to set timing and dwell to troubleshoot it properly. Remember that a dwell adjust will change timing, so once you have dwell set do a final re-time.

The fact that it ran great last year, and 2 plugs are fouled, really points to crossed wires, and maybe more than just 2. As for a compression test it's so unlikely that 2 cylinders failed at the same time that I'd hold off on that. Once you confirm firing order you can pull plugs, re-connect to plug wires, and confirm you have a strong spark on each.

Okay, I checked the firing order - it is correct. Set the dwell to .017. I do not see any cracks in the distributor cap, the wires look fine (checked ohms and they seem consistent). But now it won't start - no spark at the plugs. Could it be the coil? 12 volts going to both coil and points. I have not found the gap setting yet, but they were fine last year.

I'm thinking of replacing the wires, distributor cap, rotor, and possibly coil. Not much else to throw at it.

Set the dwell to .017 - Since it does not run at all now I'm wondering if you set the points on the low point of the cam rather than the high point

Good point Gary.

Mark, if he's getting no spark at plugs at all it's not just timing, they should spark regardless of distributor position.

I am guessing the back two plugs were fouled looking, Did you run it long enough to clear up the old fuel? Had that problem on an old truck that had been sitting for a bit.

But now it seems like you have other problems.
I would think about starting over getting eveything back like it was and see what happens.
Mike

skibums wrote: I've gone from bad to worse... Now, I do not have any spark to any plugs. There is 12 volts going to and from the solonoid, but only 6 volts reaching the coil. Not sure if this is correct.

This could be normal, because the voltage at the coil has gone through the ballast resister. It intentionally knocks the voltage down.

Here's the update - have taken the boat to our local marine shop. He replace the distributor cap and rotor. Still no fire to the plugs. He is suggesting that the timing chain/dizzy may be stripped? BUT he cannot loosen the distributor to check timing. He is stating that this is common in the Ford marine engines and said he will try heating it to get it to turn. I'm not sure what to do at this point.

A quick synopsis: Tuned boat up last year (plugs, wires, distributor cap, points, condenser). Winterized as usual. This spring, had a strong miss. two plugs were blackend. So far this year I've cleaned carb, replaced points and condensor, replaced ballast resister, checked firing order, set gap on plugs, checked gap on points (don't have dwell meter), disconnected tach. The firing has consistently gotten worse. Now the points won't fire at all. Any ideas?

hmmmmm. well i was gonna suggest dist cap but that has already been discussed. and as lakedog said boats do weird things. my dads friend replace the cap, coil, and points last year and he accidentally ran out of gas. when he got gas again the boat ran like crap! when we unplugged cyl 7 it ran good. turns out the distributor cap had the tiniest crack at cyl 7. dont know how running out of gas made it act up tho.

whether the dizzy turns or not, you should be getting fire at the plugs.    There may be a problem with your timing that keeps the boat from running well, but timing will not affect the spark getting to the plug, just when it gets there.   Yes, it may be perplexing, but I hate seeing a professional stumble around on your dime.   checking timing woudl be several steps down the road. now is time to figure out why you are not getting fire at the plugs. check the "pill" on your cap?   if there is current at the coil, you should get spark.   check there and follow the leads (like water)... if there is spark from the coil to the cap, but it isn't transferring to the other leads, it's only a couple of things :
1 - cap is bad, and is arcing internally
2 - rotor is not transfering spark from center "pill" to each spark wire lead
3 - *rotor* is not turning.   if this is the case, you will need to get it loose, and find out why.
4- points are not set correctly
5- condenser is bad, but generally this won't affect your spark issues, just makes your points burn out quickly.

If the dizzy won't turn, maybe corrosion is preventing grounding.

Try grounding it with a wire for a test.