Im gonna try and replace the cheap stuff like coil, sensor, ignition, and kill swiych if that doesnt fix it im.thinking of going with a davis unified ignition.

http://performancedistributors.com/p...-distributors/

I called them.and the tech guy said it hooks up with one 12v and has mechanical advance. There is also another kit sold on ebay i was looking at called mercpromarine8.

My bet is the coil. Had the one on my 454 Magnum go just like that several years ago. Run the boat for a few hours and it would die at 3000rpm. Open the hatch, check a few things, the coil would cool to a point it would let the engine fire up again.
Changed the coil out, no more problems

Are you sure it is not the kill switch?. On two different boats I have had that happen. The part that pulls of the button in the switch would age and loosen up. Go over a few small wakes and it would die. The first one drove me crazy, Years later it happened on a different boat and I knew right away what it was. I now carry a spare.

Padraig

The fuel pump should have a vent, if this (vent on the fuel pump) is capped, take it off...like yesterday...this will effect fuel pump psi.

Obviously, this vent should be connected to the flame arrestor or top of the carb. Make sure not hooked to a vacuum source or this will reduce your fuel psi also. Needs to be referenced of atmospheric pressure so the pump can run at it's preset pressure.

I would take the kill switch out the mix completely for testing - bring a volt meter and a couple of sealed inline spark checkers and go to town with it when your problem happens if it does in fact come back . I would also run this boat on a portable fuel supply to as I said post in # 11.

I would bring a fuel pressure tester also and possible take your mounted fuel rail out of the mix for testing

I had some new mechanical fuel pumps that were installed that overstoked (the arm not manu the exact same as version one ) causing high fuel pressure. Had to shim the fuel pumps for proper fuel pressure as they were dumping too much fuel especially at idle. just saying

If the fuel pump is on the block, then its an older Mark IV block. Probably not a Merc engine and sounds like its a Frankenstein engine put together with a mix of auto and marine parts.

Too high. should be 6-7 max.

10237297 that is the bolck cast number. I thought you could run either a pump on the block.or newer wuth the gen 6 blocks? Like i said im.completely new to boats and what i know about old carb motors is limited.