RideNFishCA
Cadet
- Joined
- Jul 8, 2020
- Messages
- 15
2005 Merc 115 4 stroke 1B158433 ELPT4S
Won't quite go full throttle (no tach on boat) but runs smooth. Doesn't stumble. I was having this problem with a slight surging. I can back off throttle from full a bit then go back wide open and get 1 second of more rpm then back down again. I'm down about 5 mph on boat speed.
Here is what I did - Replaced fuel screen on electric pump and cleaned VST. Replaced inline fuel filter that is between VST and mechanical fuel pump. Put OEM reconditioned and calibrated fuel injectors. Standard fuel filter is new.
Ran great after doing the above and then lack of full throttle came back. I shut off engine got full throttle back again for a bit. Then problem came back. Before doing the VST and such I tried the motor off of gas can with no improvement. Again, it runs smooth and if someone hasn't been in boat before they notice nothing. I just know since I'm down on speed and hear I don't have full throttle (again no tach at this time).
I did connect 12v to fuel pump when I had it out and it spun up but wouldn't know if it right speed without another to compare to. I know the mechanical pump does pump fuel. I hooked up clear hose to pump on outlet side and fired up engine and it pumped fuel out. I may take the mechanical pump off and do vacuum check according to service manual.
I have service manual and I wonder if fuel pressure is not adequate? I don't have a fuel pressure gauge and I understand I would have to run under load on a lake to check pressure on the fuel rail. I have only had boat for a year.
Any advice would be appreciated. This is the Yamaha power head years.
Thank you in advance.
Cheers,
Doug
Won't quite go full throttle (no tach on boat) but runs smooth. Doesn't stumble. I was having this problem with a slight surging. I can back off throttle from full a bit then go back wide open and get 1 second of more rpm then back down again. I'm down about 5 mph on boat speed.
Here is what I did - Replaced fuel screen on electric pump and cleaned VST. Replaced inline fuel filter that is between VST and mechanical fuel pump. Put OEM reconditioned and calibrated fuel injectors. Standard fuel filter is new.
Ran great after doing the above and then lack of full throttle came back. I shut off engine got full throttle back again for a bit. Then problem came back. Before doing the VST and such I tried the motor off of gas can with no improvement. Again, it runs smooth and if someone hasn't been in boat before they notice nothing. I just know since I'm down on speed and hear I don't have full throttle (again no tach at this time).
I did connect 12v to fuel pump when I had it out and it spun up but wouldn't know if it right speed without another to compare to. I know the mechanical pump does pump fuel. I hooked up clear hose to pump on outlet side and fired up engine and it pumped fuel out. I may take the mechanical pump off and do vacuum check according to service manual.
I have service manual and I wonder if fuel pressure is not adequate? I don't have a fuel pressure gauge and I understand I would have to run under load on a lake to check pressure on the fuel rail. I have only had boat for a year.
Any advice would be appreciated. This is the Yamaha power head years.
Thank you in advance.
Cheers,
Doug