wakerider09
New Member
Hi everyone, my mechanic(s) and I are really struggling with this issue:
Port Engine 8.1s mercruiser
340 Sundancer
820hrs
Fresh water
Approx. 2 months ago I started to notice that I had to give the port engine more throttle to keep the RPM's up, eventually the engine would only hit 3,200 rpms with the throttle pushed all the way forward. We've done a lot of trouble shooting which I will explain shortly, but at the current the symptoms the engine has are that it struggles to start and when it does start, it idles poorly, and when I give it throttle in neutral, it wants to stall out. Sometimes I can feather it past the point of stalling but then it hunts around the 900-1400 rpm range.
Things I've done to try and correct this issue:
1.) Compression test, all cylinders ~175psi - OK
2.) Fuel pressure - OK
3.) Spark test - OK
4.) Injector drop test - OK
I had another mechanic look at the boat, as the above noted tests were done while away on a trip. New mechanic did the following:
1.) found issue with the high pressure pump in the cool fuel module so we replaced just the high pressure pump. Boat ran fine for 2hrs, and then started to exhibit the same symptoms listed above.
2.) the same mechanic found the low pressure pump was now drawing too much juice, so we replaced the entire Gen III cool Fuel module, this did not fix the issue
3.) we then thought it could be the pickup in the fuel tank, so we hooked a fuel line to a gerry can, this did not fix the issue
4.) we changed all the spark plugs (twice)
5.) we swapped the spark plug wires from one engine to the other
6.) we put a brand new idle air control valve on, this did not fix the issue
7.) we swapped the MAP sensor, this did not fix the issue
8.) we swapped the ECM, this did not fix the issue
9.) we swapped the TPS sensor, this did not fix the issue
At this point the engine struggles to start, when it does, it idles poorly. When I give it throttle it wants to immediately stall out.
Anyone have any next steps??
Thank you.
Port Engine 8.1s mercruiser
340 Sundancer
820hrs
Fresh water
Approx. 2 months ago I started to notice that I had to give the port engine more throttle to keep the RPM's up, eventually the engine would only hit 3,200 rpms with the throttle pushed all the way forward. We've done a lot of trouble shooting which I will explain shortly, but at the current the symptoms the engine has are that it struggles to start and when it does start, it idles poorly, and when I give it throttle in neutral, it wants to stall out. Sometimes I can feather it past the point of stalling but then it hunts around the 900-1400 rpm range.
Things I've done to try and correct this issue:
1.) Compression test, all cylinders ~175psi - OK
2.) Fuel pressure - OK
3.) Spark test - OK
4.) Injector drop test - OK
I had another mechanic look at the boat, as the above noted tests were done while away on a trip. New mechanic did the following:
1.) found issue with the high pressure pump in the cool fuel module so we replaced just the high pressure pump. Boat ran fine for 2hrs, and then started to exhibit the same symptoms listed above.
2.) the same mechanic found the low pressure pump was now drawing too much juice, so we replaced the entire Gen III cool Fuel module, this did not fix the issue
3.) we then thought it could be the pickup in the fuel tank, so we hooked a fuel line to a gerry can, this did not fix the issue
4.) we changed all the spark plugs (twice)
5.) we swapped the spark plug wires from one engine to the other
6.) we put a brand new idle air control valve on, this did not fix the issue
7.) we swapped the MAP sensor, this did not fix the issue
8.) we swapped the ECM, this did not fix the issue
9.) we swapped the TPS sensor, this did not fix the issue
At this point the engine struggles to start, when it does, it idles poorly. When I give it throttle it wants to immediately stall out.
Anyone have any next steps??
Thank you.
