Dead on the water

J

jmauld

Well-Known Member
Jun 9, 2020
2,844
Carolina Beach
Boat Info
2010 Sundancer 390
2016 Sea Hunt Ultra 211
Engines
Twin 8.1l of gas guzzling iron
Went for a ride today. Got about 10 miles from the dock and both engines shut down. One after the other. I’ve been able to get one restarted but it runs poorly.

No overheat warnings.

any ideas what would cause this?

2007 mercruiser 8.1l
 
Both engines would seem to be fuel issue. Water in gas, clogged fuel filter.

There is also the no gas in tank problem. I had a friend call for a tow for a no start issue, turns out one of his kids pulled the kill lanyard.
 
scoflaw said:
out of gas
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We filled up on the last trip. Not saying it didn’t leak out but I would expect to see 250 gallons leak out.

I agree it feels like a fuel issue. But weird that both motors fed from separate tanks died within 2 minutes of each other.
 
No coincidence you recently bought gas and now both engines have issues. Have you checked the fuel separators?
 
Will check those once we get towed back in.
 
I think it's gas as well, different fuel tanks, but the gas was from the same source. If you do figure that out I'd go back to that Marina and question the gas.
 
That sucks, hope something simple.
 
Tank vent plugged up? If the tank vent is plugged, air won't backfill tank as fuel is used, will cause tank to go into a slight vacuum, and will act just like running out of gas.

Just a thought because have seen this a number if times.
 
Both engines fired right up today. Vapor Lock? That seems odd because they were shut down for two hours yesterday and still wouldn’t start back.

I pulled the cool fuel lines and there is NO water flow through those units.

Can they be dipped and cleaned by a radiator shop or are they a replace only item?

I remember seeing a post where some rebuilt these pumps, but I can’t find it now.
 
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Must have been the vapor angels. How is your compartment ventilation? Ever put a remote thermometer in the engine room?
 
It was hot in there. I opened it and let it cool off. Even after the 1.5hr tow home, the engines wouldn’t restart. But today, everything was good.

Just to confirm. If I pull one coolant hose off or the blue plug out, of the cool fuel module, I should get a strong water flow out of the module, right?
 
You need to have water flow through those units. If not the fuel pumps get hot and will vaporize the fuel. Need to clean out the lines and get water flow. Brother in law had the same issue. The marina he was at started throwing parts at it - both fuel filters, pumps and even had the fuel tank evacuated and refilled with ethanol free fuel. All in all they did $3200 worth of repairs. I ran into a friend that was a marine mechanic for many years in the grocery store and was explaining the problems my BIL was having and he advised to check the water flow through the fuel cooler. Spot on, totally clogged up on one engine and just a trickle through the other. Cleaned them out and problem resolved. He just used water hose, air a piece of wire - what ever it took to get water to flow through. After that he rana loop of barnacle buster through it for about 30 minute each.
 
Korkie said:
You need to have water flow through those units. If not the fuel pumps get hot and will vaporize the fuel. Need to clean out the lines and get water flow. Brother in law had the same issue. The marina he was at started throwing parts at it - both fuel filters, pumps and even had the fuel tank evacuated and refilled with ethanol free fuel. All in all they did $3200 worth of repairs. I ran into a friend that was a marine mechanic for many years in the grocery store and was explaining the problems my BIL was having and he advised to check the water flow through the fuel cooler. Spot on, totally clogged up on one engine and just a trickle through the other. Cleaned them out and problem resolved. He just used water hose, air a piece of wire - what ever it took to get water to flow through. After that he rana loop of barnacle buster through it for about 30 minute each.
Click to expand...

@jmauld In addition to this, the other thing that happens to these pumps is the inside paint/anodization flakes off and clogs the pump and burns it out. If you get new ones that will happen again down the road because these pumps are anything but cool. I would go with rebuilding them myself (if you can that is), but make sure the chambers are not painted. They are painted to help stop corrosion from forming like in a carburetor but that didn't do the trick.
 
I just had my fuel system replaced by Merc. They replaced the entire cool fuel module to include the pumps, both filters, regulators and wiring harnesses. All that along with having the injectors professionally cleaned. The y offered to replace with new, but the ones for the 496mag were on BO with an unknown availability date. Only catch is you have to go through an auth Merc Service Center, there is documentation that needs to be completed and you are responsible for the labor. My labor for RnR the system was $750.00 for both motors. This also includes cleaning the injector tree. I had been having issues for a few years and this resolved them. Well worth it. The new units are not painted inside and do away with the compression connection for the raw water, changing them over to barbed fittings.
 
Korkie said:
I just had my fuel system replaced by Merc. They replaced the entire cool fuel module to include the pumps, both filters, regulators and wiring harnesses. All that along with having the injectors professionally cleaned. The y offered to replace with new, but the ones for the 496mag were on BO with an unknown availability date. Only catch is you have to go through an auth Merc Service Center, there is documentation that needs to be completed and you are responsible for the labor. My labor for RnR the system was $750.00 for both motors. This also includes cleaning the injector tree. I had been having issues for a few years and this resolved them. Well worth it. The new units are not painted inside and do away with the compression connection for the raw water, changing them over to barbed fittings.
Click to expand...
It sounds like you had the old style units?
 
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