Vapor Lock? 1978 restored Nautique

any problems with your tach?
keep an open mind and just dont concentrate on it being a fuel issue.
its so fcn hard to troubleshoot a boat when the problem isnt happening in a shop setting, Im doing one now waisting my time, engine locks up after running on the water, of course the owner is a 30 year seasoned mechanic but cant work on it anymore, so he has all kinds of suggestions, but I always go back to basics, I first start with a simple compression test, thats good so far, now onto the next step......

does it fill with water? all cylinders?

I will check on the uscg approved rubber line. But if it is not, that would be a bush league error? worth checking as all these ideas are. I am making a check list for him so thanks for all the ideas.

He always works on the boat in the water vs. At his shop.

Luch, not as of yet, dont want to steal the thread here. I think he may have a bad riser? its the 4 cylinder 140, they always have head problems, so i did a quickie comp test to no avail,
im going to run it today again and let it sit and then pull the plugs and see if im getting any water in there

Luch, sorry trip, I found my problem, I was back by the engine and was having my guy hit the key, he would hit the key and sure as *************** it seemed as if it was locking, I ran the boat and let it sit again in hopes of catching some water spit and pulled the plugs, did another comp test and was getting a steady 175 across the board....I was seconds from pulling the manifold which is a bit of a project on a 140. so I sat by the engine again with the plugs out and he hit the key in hopes of seeing water spit...the beeotch fcn locked again.
Well, infukinpossible. stood up, scratched the boys, and grabbed a test light and put it on the yellow wire on the starter and told him to hit it again, light went on and the off in the crank positon...it was the ignition switch the entire time, it would hit and then cut out and seemed like it was locking....well I gave the old crotchity 30 year mechanic a bill for my time including, 14 bucks for a switch and i got the wtf?????? so i said look hear buddy, i couldve pulled your manifold, painted it, pulled the head, or mysteriously pulled your head and said i found the problem, it was a bad head gasket, gave you a bill for 12 hundies and you wouldve been more happy, but i didnt

I think Eric had the answer.. I am hoping. After running great all last summer on non-oxy premium vs just premium it started doing the same crap.. Changed the impeller and rotor but same crap.. Had my mechanic (I am loyal) with me when it was acting up and we are now installing or replacing a prestolite Ignitor ii and the coil. It did not have points but I don't think it was an ignitor ii.. But part of that piece was cracked and loose... Based on this forum and all the other things we have tried..I got a feeling this is going o do the trick. I think when the coil got too hot the piece which was cracked and loose was causing the mis fire after about 1-1/2 hours of use. We will find out tomorrow. Thanks Everyone!