My Sea Ray 7.4 starts runs but randomly stops and won’t restart

Johnrocks

New Member
Sep 26, 2023
5
Boat Info
1999 SeaRay Sundancer 270 se
Engines
7.4 454 bravo 3
This problem has been ongoing for 2 months. I have a 1999 27’ Sundancer with 7.4 454 bravo 3. It starts just fine and idles as normal. Shortly after I pull out of the slip the boat stalls and will not restart.I changed the fuel filter and cleaned the fire arrestor and added fuel additive. This seemed to do the trick but next time out it stalled again and would not start. We had a marine mechanic run tests and he replace the ignition coil. We took it for a test run and once again seemed to work fine. A few days later, we took it out for a run but again it stalled 20’ from our slip. I contacted the mechanic and he came the next day to check it out (I was not there) and said he checked it out but couldn’t find anything wrong.
I ran the boat at the dock for over an hour and all gauges are normal, ran it in and out of gear forward and reverse,stopped and started a dozen times and can not get it to stall.
We are located on the St.Clair River with heavy ship traffic and strong current so a breakdown can be very unnerving.

Any help would be appreciate.
 
I like a good mystery.

1.) It starts and runs all day as long as it is in the slip.
2.) Once you put it in gear......sometimes it will stall and not restart.

The mystery is what is causing the engine to shut off and not restart.

So a few questions:

-Did your mechanic check for stored codes on the ECM?
-When the engine did run for a while ........what RPM did it get up to?
-When you say it does not restart.....does the engine crank?
-Is this boat new to you?

There are plenty of things that will cause an engine to shut down. There are far fewer things that will keep it from restarting.
 
I like a good mystery.

1.) It starts and runs all day as long as it is in the slip.
2.) Once you put it in gear......sometimes it will stall and not restart.

The mystery is what is causing the engine to shut off and not restart.

So a few questions:

-Did your mechanic check for stored codes on the ECM?
-When the engine did run for a while ........what RPM did it get up to?
-When you say it does not restart.....does the engine crank?
-Is this boat new to you?

There are plenty of things that will cause an engine to shut down. There are far fewer things that will keep it from restarting.
The boat has stalled 3 times ... first time at the slip while warming up. The second and third in the marina a short distance away from the slip. In all cases, the motor was warmed up at least 10 minutes and you could not restart for at least 2 hours.
1. I do not have an answer for the ECM Question.
2. After my initial attempt at solving the problem I had the boat up to 3000 + rpm. After the ignition coil was installed we did a test run at close to 4000 rpm.
3. Yes, the engine will crank.
4. I’ve had the boat 6 years. First time with an issue like this.
 
Sounds like something is shutting it down
 
Not real familiar with '99 7.4 454s. Fresh or salt water cooled? Do you have an isolated fuel cooler?
Why I ask - BIL had a motor that did similar. Although it was a Volvo with duoprop drive. They changed out everything - fuel filter, pump, fuel in tank, fuel lines, even cut the tank out of the floorboard and replaced it. Don't know all the details as to what supported everything they did. Threw tons of $$$ at it and nothing worked. Did very similar to what yours is doing. Start and run at the pier for hours at relatively low rpms, did fine when put in and out of gear (at the pier). Took it out and soon as tried to go on plain, shut down.
I bumped into a retired marine mechanic I knew in the grocery store one day and asked him what he thought. Said to check the fuel cooler. They can get blocked up over time, especially with motors that have sterndrives (no stainer). The water flow gets reduced and therefore the cooler does not do its job and fuel vaporizes. After things cool down (a couple of hours) moter starts back up and cycle continues.
Maybe this pertains to your motor set up, maybe not. Just a thought.
 
Not real familiar with '99 7.4 454s. Fresh or salt water cooled? Do you have an isolated fuel cooler?
Why I ask - BIL had a motor that did similar. Although it was a Volvo with duoprop drive. They changed out everything - fuel filter, pump, fuel in tank, fuel lines, even cut the tank out of the floorboard and replaced it. Don't know all the details as to what supported everything they did. Threw tons of $$$ at it and nothing worked. Did very similar to what yours is doing. Start and run at the pier for hours at relatively low rpms, did fine when put in and out of gear (at the pier). Took it out and soon as tried to go on plain, shut down.
I bumped into a retired marine mechanic I knew in the grocery store one day and asked him what he thought. Said to check the fuel cooler. They can get blocked up over time, especially with motors that have sterndrives (no stainer). The water flow gets reduced and therefore the cooler does not do its job and fuel vaporizes. After things cool down (a couple of hours) moter starts back up and cycle continues.
Maybe this pertains to your motor set up, maybe not. Just a thought.
Hi Korkie..I’m fresh water
This sounds like a very good suggestion. I’m meeting a friend who has much more knowledge than I do about Merc motors later today. I’m going to look and see if this might apply to my boat. I don’t want to get into the parts replacement hole so I hope this is it. Thanks for your help. Much appreciated and will keep you posted.
 
The key to solving this is understanding why it is taking two hours before it will restart. That is the weird part. That seems like a safety is being tripped or a limit is being reached which tells the ECM not to fire the plugs and injectors. There would definitely be codes stored in the ECM if this were the case.

Alternatively.....outside of the ECM the prime suspect would be the fuel system. Since you have owned the boat for 6 years and this is a new problem.....I would have your mechanic check the fuel pressure. A failing fuel pump would account for the intermittent stalling and difficulty in restarting.
 
The key to solving this is understanding why it is taking two hours before it will restart. That is the weird part. That seems like a safety is being tripped or a limit is being reached which tells the ECM not to fire the plugs and injectors. There would definitely be codes stored in the ECM if this were the case.

Alternatively.....outside of the ECM the prime suspect would be the fuel system. Since you have owned the boat for 6 years and this is a new problem.....I would have your mechanic check the fuel pressure. A failing fuel pump would account for the intermittent stalling and difficulty in restarting.
My friend and I spent about 3 hours going over the motor with no definite conclusion. Still can’t get it to stall and have ordered the adapter for his meter to my boat so we can check stored codes.
Considering replacing the fuel pump…..if I can locate it LOL.
 
Determine what it's not getting when it cranks and doesn't start, fuel or spark. That ecm will not store any codes that will help you. If I were to guess I'd say the pickup coil in the dist.
 
Determine what it's not getting when it cranks and doesn't start, fuel or spark. That ecm will not store any codes that will help you. If I were to guess I'd say the pickup coil in the dist.

The weird part is what is going on that it cranks and doesn't fire for a couple of hours after a stall. Should be easy to at least get a fuel gauge on it to see if it has pressure on the rail. That would tilt the table to an electrical issue pretty quickly if the rail pressure was okay.
 
+1 on Scoflaw - The same goes with fuel pumps. When they get hot they do not work as they vaporize the fuel. Checking the fuel cooler costs nothing and rue that part of it out. I do agree ruling things out such as fuel issue or spark issue is the way to go. This is part of ruling out the fuel issue. I never heard of this before it happened to my BIL, although the retired mechanic I spoke stated it happens more often then one would think. Most times it is after many $$$ have been spent on replacing perfecty good parts. Make sure what you is is malfunctioning before you replace. As scoflaw said, check for spark when it will not start. No spark, consider replacing the coil pack. As as playdate said, check the fuel pressure in the fuel rail. No pressure, no fuel - or it has vaporized and will give you a no or extremely low reading.
 
have you tried starting it with the throttle applied?
 
Put a plug tester on it and check for spark
 

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