502 Mag MPI Gen VI Hot start issue
03-08-2021 | 04:14 PM
#31
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From: SW Florida
If you want the problem gone for good, just run the return back to the tank. It is an easy fix and it doesn't require any sort of check valve. Just unscrew the return line from the filter head and plug the hole in the filter head. Hook a hose to the return line and hook it to a barb on top of your fuel tank. This works 100% of the time in my experience. No need to reinvent the wheel for an easy fix
Genuine Mercury & Mercruiser parts. FUEL FILTER(FUEL COOLED SYSTEM) S/N 0K147350 & UP
03-08-2021 | 04:25 PM
#33
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From: SW Florida
One tank with separate fuel pickups (one for each engine) and an unused pick up for a generator that is missing. The basics concept is easy to understand but the details are what would get me. Just need to find the port to cap off and what line to run back to the tank. Im assuming I can put in a T Fitting so both return lines lines could share the Gen pickup.
03-08-2021 | 04:30 PM
#34
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From: KY
The filter head will have arrows pointing out and in, or list IN and OUT. One of the 2 lines will be connected to the inlet (arrow in), this is the return line.
The other side of the filter head will be the line coming from the tank with a arrow in
The other side of the filter head will be the line coming from the tank with a arrow in
03-08-2021 | 04:37 PM
#35
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From: On A Dirt Floor
Depends how big that 1 generator port is. I doubt big enough for two pumps.
At idle nearly 99% of your fuel will be going thru that 1 port. Remember, electric pumps pump 10O% their volume all the time. Little fuel goes thru injectors at idle/low speed, rest goes thru return.
If your going to return into fuel fill hose, i’d fo something like this but with two return connections.
https://www.cpperformance.com/c-500-...s-returns.aspx
At idle nearly 99% of your fuel will be going thru that 1 port. Remember, electric pumps pump 10O% their volume all the time. Little fuel goes thru injectors at idle/low speed, rest goes thru return.
If your going to return into fuel fill hose, i’d fo something like this but with two return connections.
https://www.cpperformance.com/c-500-...s-returns.aspx
03-08-2021 | 06:54 PM
#36
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From: Cape Coral FL
Yes, that #6 fitting is where you will plug it. You need a 1/4 npt plug. A 3/8 rubber fuel line will slip right over the line that you disconnected. An easy check to see if the 1 return port is big enough for both engines, check your fuel pressure at idle before and check it again after with both engines idling. If the fuel pressure is the same, you are good. If the fuel pressure is higher, you will need a bigger or 2 separate returns. I have returned 2 engines to a single 3/8 npt return in the top with no issues, but you will just have to try it. If that fitting in the top of your tank has a pickup tube on it, I would remove it and just screw in a fitting to dump the fuel in tank without pushing it through a pickup tube.
03-12-2021 | 02:29 PM
#38
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From: SW Florida
Update. Ran the boat kind of hard/easy for about an hour and went to dinner last night. Raised the engine hatch and came back to a nice normal start. The wireless kit came in so I did the install this afternoon. It looks like its really well made for outdoor use as all the electronic guts were hot dipped in some sort of hard rubber. Hid the receiver in an easy to get to location and tested it to abut 100ft. Up and down as advertised. The return fuel line is still on the books when its not so perfect outside.
https://shop.atcomp.com/g3-e01
Thanks again to everyone who helped me find the exact problem and various solutions.
https://shop.atcomp.com/g3-e01
Thanks again to everyone who helped me find the exact problem and various solutions.
03-15-2021 | 12:39 PM
#39
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From: New Baltimore, MI
Twin engine and both engines exhibit the same problem. Go out for a run and shut down to grab lunch. Hour later, they try to start and will run for a second or two before dying. Both act like they are starved for fuel. I checked the fuel/water separator and no water in system. Let it sit for another hour and after a few cranks, they fire up like it never happened. Get home, tie up and restart to flush without issue. Its just that magic 'hour' after I let it sit. Happened many times.
Fuel tank vent line? Ill check and replace both fuel filters in the AM (8 months old), but it seems like a heat related issue. Fuel and heat is the only thing the two engines share? Both are bone stock with about 30 hours on rebuilds.....nothing fancy like blowers or aftermarket EFI/Carbs.
Tonight I almost had to call the Tow Of Shame in front of a packed boaters bar. I just hid down below for a few hours and came home alone in the dark after I got one engine to start up. And this time I verified I had about a half tank of gas (Yea...I did that once after a faulty fuel sender).
Ill try anything as mechanics are backed up at least a month.
Thanks in advance.
Fuel tank vent line? Ill check and replace both fuel filters in the AM (8 months old), but it seems like a heat related issue. Fuel and heat is the only thing the two engines share? Both are bone stock with about 30 hours on rebuilds.....nothing fancy like blowers or aftermarket EFI/Carbs.
Tonight I almost had to call the Tow Of Shame in front of a packed boaters bar. I just hid down below for a few hours and came home alone in the dark after I got one engine to start up. And this time I verified I had about a half tank of gas (Yea...I did that once after a faulty fuel sender).
Ill try anything as mechanics are backed up at least a month.
Thanks in advance.
He changed fuel source and went to no alcohol fuel.
03-15-2021 | 03:38 PM
#40
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From: Miami, Fl
Vapor Lock "No - More"
Good afternoon fellows. I bought a 32 Hustler over 6 years ago with twin 502 MPI's, this issue happened to me the first time I took the boat out, and of course it happened to one engine all the time until it happened to the other engine one hot day in Hot Miami. The problem drove me crazy for one whole year! It occurred to me that vapor lock happened more often when it was really hot out. Apparently the issue is that the fuel gets hot and causes the VST box to lock-up, so my solution was to run the engines as cold as possible. I removed the factory water pumps and thermostat housings
with "thermostats" and installed crossovers with stainless steel thermostat housing, (without thermostats), and run my engines at very cool temperatures, less than 100 degrees. Guess what, PROBLEM SOLVED"!!! Not one engine cut-off or failure to start after running hard, for the last 5 years.....by the way I also run REC 90 fuel which reduces water vapor in the fuel tank and the engines run a lot cleaner.
with "thermostats" and installed crossovers with stainless steel thermostat housing, (without thermostats), and run my engines at very cool temperatures, less than 100 degrees. Guess what, PROBLEM SOLVED"!!! Not one engine cut-off or failure to start after running hard, for the last 5 years.....by the way I also run REC 90 fuel which reduces water vapor in the fuel tank and the engines run a lot cleaner.
