Random Engine Shut Down

J

jrhalling

New Member
Jul 13, 2012
12
Seattle, WA
Boat Info
1991 420/440 Sea Ray Sundancer
Engines
Twin 7.4L Mercruiser Inboards
We have a 1991 Sea Ray 420 Sundancer with twin 7.4L big blocks. We have a problem with the port engine just shutting down after about an hour of running time. We have had the tanks cleaned; checked all of the fuel lines and fuel directional valves for fuel flow, put the solenoids in the manual position to ensure full fuel flow, blown back through the fuel lines in to the tanks to insure that there is no obstruction in the fuel pick up tubes, replaced all of the in line fuel filters, just recently replaced the raw water impeller on the port engine, and have purchased a small electric fuel pump to make sure that we can pull fuel all the way to the fuel water separator before it goes in to the mechanical fuel pump. As I mentioned before; after initial start up the boat will run just fine for approximately an hour before it just shuts down and then will not restart. Any ideas or suggestions on what I could pursue next to see if I can remedy this issue? Any ideas would be greatly appreciated. Thanks
 
Hello JR we need some more info to help. Understand the the one hour time frame but what rpm is it running at when it dies? Any other facts that you can tell us would help. I'm talking about things like the previously mentioned rpm's, on plane, not on plane, dies immeadiatly, stumbles then dies, hours on engine, what temp is the engine at, etc. One thing I would do if it were me trying to deal with something like this would be to pull some spark plugs right after it died and inspect them.
 
Hi Gary, Thank you very much for viewing my thread. The engines were running at about 1,100 rpm's; just putting along. After an hour of running we can notice the engine synchronizer start to fluctuate and then the engine dies. I have pulled the flame arrester off and had my wife give the port engine throttle a couple of quick blasts and noticed that there is no fuel coming from the accelerator pump in to the primary throttle bores of the carburetor, so I can not figure out what is interrupting the fuel flow. I am going down tomorrow to inspect and probably clean out the heat exchanger expecting that perhaps some of the pieces of the exploded water impeller might be lodged in the element and causing a thermal issue that causes the shut down. The weird thing is that the temp gauge at the helm does not show any indication of over heating.?????????
 
Hi Gary, I did pull a plug or two and they are dry and show that they are burning properly.
 
Have you inspected the fuel hoses/lines themselves? If the engine is starving for fuel it could be that the lines are old and the suction from the pump is effectively closing the hose and blocking the fuel flow. You may not necessarily notice a collapsed hose because it could be the inside lining of the hose has detached from the outer layers. If the fuel lines are original, I would consider checking for fuel flow at various places after the motor dies and if needed replacing them.

 
Maybe a fuel tank venting issue? Can't tell if your previous work included checking this. Locate your tank vent on that side and see if it's stopped up. Spiders and such can block them. If you experience the issue again, you could remove your filler cap and listen for a "sucking" sound of air rushing into the tank. If your boat has crossover fuel feed, you could switch over to the starboard tank and see if it fires up.

Good luck!
 
Did you check the screens that are INSIDE the pickup tubes? You cant se them just by removing the pickup tubes. You need to remove the tube and then unscrew the tube from the fitting. The screens are inside there. I had the same issues for a long time and found them by accident. I don't know if you have them but I did on my 87 270. I eliminated them and use a separator. If you shoot me your email address I can send pics. I couldn't believe it ran at all. But like you, it ran for awhile then quit. I also thought it was a vent issue.
 
Although I have a Chaparral, I read many of the posts here since I have many friends with SeaRays. I have experienced the same problem with my single 7.4 that has a carb, once last year and again about a month ago. Mine would not restart until I removed the fuel separator and reinstalled. What my marina and I finally did was check the rubber fuel hose from the tank to the filter and discovered that it was collapsing and starving the engine for fuel. I have replaced it and all seems fine now. The old hose looked fine from the outside but we could tell it had little black specks coming off of it and we are sure it was collapsing like a straw. Removing the fuel filter allowed the collapsed line to open up temporarily. Mine happened both times at 3000 RPM's.
 
NH Tooner said:
Did you check the screens that are INSIDE the pickup tubes? You cant se them just by removing the pickup tubes. You need to remove the tube and then unscrew the tube from the fitting. The screens are inside there. I had the same issues for a long time and found them by accident. I don't know if you have them but I did on my 87 270. I eliminated them and use a separator. If you shoot me your email address I can send pics. I couldn't believe it ran at all. But like you, it ran for awhile then quit. I also thought it was a vent issue.
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