Boat stalls and will take a while to restart

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bbruno

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Feb 15, 2003
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11152
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87 Mercruiser 5.7l alpha 1 gen. Thunderbolt 4 ignition.
Cruised to catalina island Saturday morning and boat ran perfect, about halfway from avalon to two harbors 11 miles away but killed. Boat restarted fine after a few minutes and we headed out and about 10 min later same thing, when we were moving I stayed a little over idle and when I gave it gas it killed. We made it to two harbors fine as it idled great but if I gave it throttle it died again. Tried adding fuel to the carb and it didn't make any difference I had to wait a few minutes till it would start.. any ideas?
I checkled electrical connections. And pulled the distributor cap and didn't notice anything.

Wanted to add that on 1 particularly big swell that had a pretty good drop and hit it died immediately on impact. And also in the mooring I can start it and throttle it up and it's sound perfect
 
Take a clean, clear milk jug and funnel and dump the contents of the fuel filter in it. Wait a few minutes and see if it separates and shows water present. If you don't have a spare filter on hand, put a drop or two of oil on the gasket and put the old on back on. Take the fuel you took from the filter and use it in a lawn mower (unless it's all water).
 
Running out of fuel. Float bowl goes empty. Likely float valve is sticking...not letting fuel in. Another possibility, floats are 'water logged' if plastic or has a leak if brass.

Always check filters in case that's the problem.

After re-reading, Throttle up and dies is fuel related but adding fuel to carb...either you flooded it or not enuff fuel. If you did it right, the cause can go to electrical even thoufh it doesn't sound like it yet. Dying on bump can go either way at this point.
 
Could be a clog in the tank at the pickup or maybe a fuel line collapsing.
 
I'm leaning towards electrical because I added fuel to the carb the 1st time it died and it still took its time to restart but if it was already flooded that would be the same as thing.
I suppose if I had an excessive amount of water in the separator it could cause something similar but when it's running it purrs and in my experience when I have water in my separator it misses.
 
Change the filters, check for water in them and check all electrical connections especially the multi pin wire harness and battery terminal connections.
 
Give a time frame how this happens. When it fixes itself, do you just let it sit? How long before first stall. Maybe coil getting hot and starting to fail. Coil failure doesn't require engine to come up to temp.
 
First time it stalled I just traveled about 30 miles and was doing about 10 knots at the time of stall, after that it was kind of random because I just idled about 6500 rpms.occasionally I would throttle it up and it would die. I let it run in my driveway last night for over an hour at a little over idle and it was perfect. When it dies it takes a couple minutes and fires right up
 
In a situation such as this, I always check that the fuel tank vent is "free flowing". Our mud daubers love fuel tank vents. And the check is quick, easy, and free.
 
Pull my water separator and it had a lot of particulate in it but luckily my carburetor filter seem to be ok. I've never had a water separator clogged before I've only had one with water in it but I assume it acts the same as a filter also have any of you guys ever had one get clogged
 
Carry a spare incase of future issues. Junk got in your tank somehow.
 
Do you have points still or electronic ignition? I had something similar, the points and condenser were going, the coil would over heat and then it would kill. I could let it sit for a bit until it cooled off and then it would run for a bit and die again. Switched to electronic distributors and the problem is gone.
 
It's a thunderbolt 4 electronic ignition but I am replacing the coil because it's a cheap fix just to be on the safe side although I've only had coils fail completely and never intermittent
 
Bad kill switch or weak lanyard can cause stalling problem. It will run at idle but put it in gear, hit small wake and it dies. Had this happen on two boats. The UV eventually weakens the clip.
 
Make sure you get the correct coil. It runs with any internal or external resistance. It runs straight off the 12v from the batt.

Something else that happened to me that was similar. It was the ignition module. I hope you can get this link for TBIV ignition...

http://www.boatfix.com/merc/Techbk/94/94hg4b.pdf
 
I just put the new filter on and Ran it. It finally died while i could check. Had 12v to coil and no spark so I put the new coil on and it fired right up, of course that's what it has been doing also so it could very well be a coincidence.. it only ran for a minute so it wasn't hot yet. I'm really hoping for an intermittent coil. Now granted it could still be several things but I have to start somewhere. I'm supposed to go scuba diving sunday
 
We had an odd MerC 5.7, with EFI that used a high pressure pump mounted in a Vapor Separator Tank (VST). The VST had a float like a carburetor and an engine-mounted mechanical fuel pump filled it. We could run for hours. Shut down for about 30 minutes and it wouldn't start... Or, if it did start, it'd quit in a few minutes of running. We replaced the expensive high pressure pump in the VST and did not solve the problem. I thought it was a vapor lock and actually carried a bilge blower with alligator clips to cool the VST and fuel pump area.

Then I replaced the mechanical fuel pump, pretty much on a whim. Solved the problem. Same as yours? Maybe. Maybe not. But I determined that the engine would quit, starving, several minutes AFTER the pump failed to provide gas to the VST. It was when the VST ran dry that the high pressure pump didn't have gas to send to the EFI. If a similar pump failure happened on your 5.7, it wouldn't quit till the carburetor bowls ran dry.

I say this realizing you've tried priming it with gas, but thought I'd still share my experience.
 
Fuel pump is a year old but it was one of my 1st thoughts, the ignition module is something I'm aware of that can cause this same issue but it will be one of the last things I try because it's the most expensive.. I just wish what ever is causing this would fail all the way so I could actually troubleshoot it
 
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