HELP!? 351w wont start warm!

So I have asked many mechanics to take a look at my boat, and we can't figure this one out.

Let me know your thoughts (the guys on here really seem to know their stuff!) I'll let you know what I've tried already.

It's a '74 nautique. 351w reverse rotation. New plugs, starter, plugs, battery.

Simply put, it won't start when it's hot. BUT HERE'S THE KICKER! It starts fine, hot or not, in my driveway hooked up to the hose.
For some reason, once it's out on the water, as soon as I shut it off, it won't start for about an hour.

Any ideas?!?
ps I have searched but I couldn't find this problem...

Teddee -If you buy a 'Blaster II' make sure it is the Epoxy version -if you want to install it on it's side. A regular Blaster II has to stand vertical.

A worn needle & seat in the bowl would cause flooding. Have you ever rebuilt the carb?

Im wondering if it's the distributer. Any ways to test it? Im getting spark, but maybe the timing is off when it's hot?
Also, im going to check the timing again, one time the bolt got loose and it changed itself... Im wondering if it did it again.
Thanks for the help so far guys.

Please clarify, won't start or won't turn over when hot?

Teddeee1981 wrote: Full throttle VS regular throttle. Is there a difference the way the carb reacts?

Yes, the further you engage the throttle, the more the butterflies open. More throttle = more air. Based on the symptoms youre describing, Id bet good money that your carb is leaking after shut down. Pop the flame arrestor off and have a look.

critter wrote: So what do you do with Bad money there Tim ??

He uses it to buy Bilgecote.

My buddies boat was doing the same thing...or at least the same thing I think.

The...coil I believe was the culprit. Is that the mechanical device with two screws on it? I think they used a screwdriver to bridge the screws to override the thing and it started great. Would that make sense? I'm not mechanically inclined enough to make this a for sure thing. But I THOUGHT that's what they did....

Make any sense at all or was I not in the proper state of mind when I heard that?

That's what my buddy's boat was doing....it would run like a champ...pull some acts, turn it off and it would not start. Turn over like a son of a B but wouldn't fire. Just seemed like there was no spark. It was weird.

Really made us mad lol

8122pbrainard wrote: critter wrote: So what do you do with Bad money there Tim ?? He uses it to buy Bilgecote.

Ha, GD bilgekote. Ive got a gallon of white and a gallon of gray... probably wont use the stuff again!

Coils can certainly overheat and cause the boat not to run once it warms up. However, if the symptoms only rear their ugly head when a warm RESTART is attempted, then Im still guessing carb leak after shut down.

Tim, having the initial timing too far advanced will cause a hard start warm or cold, right?

Bri892001 wrote: Vapor lock issues is another possibility?

What is vapor lock???

skicat2001 wrote: What is vapor lock???

I don't know all the science behind it, but it basically has to do with a fuel line that's not under pressure gets too hot. The gasoline starts to evaporate in the line and causes a little air bubble.

Newer cars never have this problem anymore, because the gas is pushed so hard from the in-tank fuel pumps (part of the fuel injection system). It's more a problem when gasoline is being pulled (rather than pushed) from engine mounted mechanical fuel pumps common in older cars and boats.

I know there are kits out there, that some of the newer, but pre-fuel injection boats have already and you can retrofit.

But yeah, worth double checking the timing too.

I remember a post several years ago from one of our past members that has what I consider very good engine skills. He stated (in his very "frank" terminology), that marine engines do not vapor lock. The reason being is they do not see the heat under the dog house like a automotive engine sees under it's hood. I happen to agree with him. I have never see a marine engine vapor locked.

Have you checked the exhaust manifolds for leaks? They could be leaking water into the motor and keeping it from firing up. Water won't compress and slower cranking is a sign.

Do 74's have anything at all in the way of relays that could affect this?

I know anything electrical can be less conductive when hot. Hence starter motors always acting up more when a car is fully warmed.