New member here, looking for recommendations and advice for getting our boat running right. Thanks for taking the time to read my post and sharing any insight you might have. I share a lot of detail below so bear with me:
Background: We have a 2004 Johnson 60 HP, four-stroke, fuel injected pushing our 20-foot Pontoon boat (max 23 MPH, GPS verified). We purchased from a dealer in 2015 with only 90 hours on her (little old lady drove her to church!) The boat now has 197 hours on her and has been a fantastic boat especially as our first ever boat. We had her delivered to our dock, so no trailer. I’m a shade tree mechanic mostly working on cars and service the boat each year on our boat lift by backing her in and raising just enough for me to access the oil, plugs, lower unit, etc. from the dock.
The problem: The boat will start effortlessly every time, idles perfect and runs fine as I throttle up, but begins to surge, very rhythmically (one, two, one two) if I push her past 8 MPH. I do not have a working tachometer; I use the depth finder GPS to track speed so that is how I know it is a consistent problem at that speed. We took her out last weekend and cruised for over 20 minutes; she ran very smooth and consistent so long as I stayed below 8 MPH.
I’ve loaded an 18 second video to YouTube showing what we are experiencing (boat is on the lift, in neutral while running): 0-5 sec in video at idle, all good. 6-10 seconds into video under partial throttle, all good. 11- 18 seconds at half-throttle and she develops a very rhythmical surge that is constant.
The problem first surfaced earlier this year. I borrowed a trailer and pulled her out of the water for the first time since 2015 to change the impellor. She was not giving me any issues; I just knew it was a service that needed to be done especially since I’d not done it in six years. All went well with the install but I didn’t give her a full up test drive when we finished, I just made sure she was pushing water when we launched and cruised back to our dock, five minutes max as we have a boat launch on our property. We were in a bit of a hurry due to deteriorating weather conditions and to return the trailer. I also changed the fuel filter while I had her out for the impellor work.
A couple of weeks later I took her out for the first time and this is when the surging problem first showed up. The motor will surge whether or not I have her in gear, under a load so I think I’ve eliminated a lower unit/prop issue.
However, could we have done something wrong during the impellor work or is this just a coincidental issue?
What we’ve done so far:
First, thinking it must be fuel delivery by the way she was running:
Again, I appreciate any insight provided and look forward to getting this trusty old gal back up to full speed. Thanks for your time!
Semper Fi - Bill
Background: We have a 2004 Johnson 60 HP, four-stroke, fuel injected pushing our 20-foot Pontoon boat (max 23 MPH, GPS verified). We purchased from a dealer in 2015 with only 90 hours on her (little old lady drove her to church!) The boat now has 197 hours on her and has been a fantastic boat especially as our first ever boat. We had her delivered to our dock, so no trailer. I’m a shade tree mechanic mostly working on cars and service the boat each year on our boat lift by backing her in and raising just enough for me to access the oil, plugs, lower unit, etc. from the dock.
The problem: The boat will start effortlessly every time, idles perfect and runs fine as I throttle up, but begins to surge, very rhythmically (one, two, one two) if I push her past 8 MPH. I do not have a working tachometer; I use the depth finder GPS to track speed so that is how I know it is a consistent problem at that speed. We took her out last weekend and cruised for over 20 minutes; she ran very smooth and consistent so long as I stayed below 8 MPH.
I’ve loaded an 18 second video to YouTube showing what we are experiencing (boat is on the lift, in neutral while running): 0-5 sec in video at idle, all good. 6-10 seconds into video under partial throttle, all good. 11- 18 seconds at half-throttle and she develops a very rhythmical surge that is constant.
The problem first surfaced earlier this year. I borrowed a trailer and pulled her out of the water for the first time since 2015 to change the impellor. She was not giving me any issues; I just knew it was a service that needed to be done especially since I’d not done it in six years. All went well with the install but I didn’t give her a full up test drive when we finished, I just made sure she was pushing water when we launched and cruised back to our dock, five minutes max as we have a boat launch on our property. We were in a bit of a hurry due to deteriorating weather conditions and to return the trailer. I also changed the fuel filter while I had her out for the impellor work.
A couple of weeks later I took her out for the first time and this is when the surging problem first showed up. The motor will surge whether or not I have her in gear, under a load so I think I’ve eliminated a lower unit/prop issue.
However, could we have done something wrong during the impellor work or is this just a coincidental issue?
What we’ve done so far:
First, thinking it must be fuel delivery by the way she was running:
- Bypass the new fuel filter with a hose adapter to isolate the fuel filter. No change.
- Disconnect the fuel line from tank and run the motor from a fresh can of fuel. No change.
- Verify the gas tank vents are working – removed, cleaned. No change.
- Verify the bulb stays firm while the engine is running. All good. No change.
- Checked fuel line motor connection. No change.
- Drain fuel (about 16 ounces in a water bottle) from Fuel Vapor Separator – looked good.
- Spray carb cleaner around all fuel lines while running to see if something changes. No change
- Replaced the fuel pump (I just knew that $150 part was going to fix it!) No change.
- Change spark plugs – old plugs (less than 20 hours on them) showed no unusual signs of wear.
- This weekend I installed two new coil packs with new wires (one coil feeds two plugs) no change.
Again, I appreciate any insight provided and look forward to getting this trusty old gal back up to full speed. Thanks for your time!
Semper Fi - Bill
