wharfcreek
Seaman Apprentice
- Joined
- Jul 31, 2009
- Messages
- 36
I have a 2017 Yamaha 115 4-stroke with just about 115 hours on it. I purchased the boat/motor just over a year ago with 80 hours on it, and since purchase it's run 'normally'. 2 weeks ago I set out on a morning cruise on the Chesapeake Bay, and engine started and ran well for all of about 30 minutes or so. Then, it was like someone it the 'off' switch but left the engine running on one cylinder. For the record, the engine did NOT stall completely. But, it seemed to die on 3 of the 4 cylinders, and barely made it back to my dock. This next hour and a half of 'idling' home consisted of mostly just one-hole running, but every few minutes or so the engine would seem to 'gasp' some and maybe hit on 2 or 3 cylinders....then back to just one.
I pulled the boat out and took it to the local marina / Yamaha dealer. Unfortunately, after sitting for 2 weeks they were still unable to do more than just run the boat once and confirm the above poor running condition. They thought maybe 'spark plugs'? From the way it failed, as in running perfectly then an immediat loss of power and down to one cylinder firing, I was incline NOT to consider this as a valid cause.
So, 2 days ago I pulled the boat home, and I spent most of yesterday doing my own trouble shooting. Engine OIl was at full mark and undiluted. I pulled and replaced all 4 spark plugs just for good measure, but they all looked fine, and if anything maybe appeared fuel-starved? A small black soot spot but otherwise mostly white in insulator color. I check the main fuel/water separator filter and found no evidence of water or any other fuel contamination. Filter had just been replaced about 30 days ago when I took the boat back to the Dealer to have Lenco Electric Trim Tabs installed and to have the 'spring service' completed. Anyway, I decided to dig deeper, and I pulled the intake manifold and removed the VST. I did the bench disassembly and found absolutely nothing wrong!! In fact, it all looked 'new'! And, it was full of fuel when I removed it. I did test the HP Fuel pump on a 12V battery and the fuel pump also seemed to operate perfectly. I tested the float valve, and again, no problems. So, I re-assembled it and reinstalled it. I did NOT remove or test the Lift (or low pressure fuel) Pump, but given the VST was full of fuel, that rather told me that the low pressure pump was operating as it should. The ONLY other thing I did was to replace the small in-line fuel filter that is between the VST and the lift pump. It didn't look bad, and I saw no contamination or indicators or any problem in that canister. But, I had a new 'spare', so I replaced it.
After all this, I grabbed a hose and test ran the engine. And, as fate would have it, it fired up and seemed to idle smoothly on all 4 cylinders while on the trailer. I even 'revved' the engine and it seemed to run up well. I don't 'over-rev' while un-loaded, so I only spin a free-revving motor to about 3K RPM, but at that level it held on to running smoothly, so from all appearances my problem may be 'fixed'. BUT...... I don't think so! I'll know later after I launch the boat and try to run it some. I also bought a plastic bottle of that Yamaha 'Ring-Free' fuel additive? Like $68 for a quart of the stuff!!!???!!! Really? Was I a sucker, or what!! Anyway, I'm going to mix up a 'shock' batch of that stuff and add it to my gas tank. I guess it can't hurt.
So, what I'm looking for here are any other ideas or suggestions regarding the problem as described and the repair attempts I've noted above. From where I sit, I didn't really 'fix' anything! Given the VST was full of gas, I'm incline to think that anything up to that point was probably OK, meaning the small in-line filter was NOT clogged, and the lift-pump was functioning normally as it should. Had I found some indication of contamination within the VST, or a non-functioning HP pump, again, I might have felt better about maybe having ID'd the problem. But, as stated, this looked like a brand new component, right down to the internal screen-filter on the end of the HP Pump itself. So, I'm baffled! I'm also a bit 'miffed' that an reasonably new motor with less than 125 hours would exhibit this kind of problem. But, Cest La Vie!
Any help or suggestions would be greatly appreciated. Many thanks! Tom D.
I pulled the boat out and took it to the local marina / Yamaha dealer. Unfortunately, after sitting for 2 weeks they were still unable to do more than just run the boat once and confirm the above poor running condition. They thought maybe 'spark plugs'? From the way it failed, as in running perfectly then an immediat loss of power and down to one cylinder firing, I was incline NOT to consider this as a valid cause.
So, 2 days ago I pulled the boat home, and I spent most of yesterday doing my own trouble shooting. Engine OIl was at full mark and undiluted. I pulled and replaced all 4 spark plugs just for good measure, but they all looked fine, and if anything maybe appeared fuel-starved? A small black soot spot but otherwise mostly white in insulator color. I check the main fuel/water separator filter and found no evidence of water or any other fuel contamination. Filter had just been replaced about 30 days ago when I took the boat back to the Dealer to have Lenco Electric Trim Tabs installed and to have the 'spring service' completed. Anyway, I decided to dig deeper, and I pulled the intake manifold and removed the VST. I did the bench disassembly and found absolutely nothing wrong!! In fact, it all looked 'new'! And, it was full of fuel when I removed it. I did test the HP Fuel pump on a 12V battery and the fuel pump also seemed to operate perfectly. I tested the float valve, and again, no problems. So, I re-assembled it and reinstalled it. I did NOT remove or test the Lift (or low pressure fuel) Pump, but given the VST was full of fuel, that rather told me that the low pressure pump was operating as it should. The ONLY other thing I did was to replace the small in-line fuel filter that is between the VST and the lift pump. It didn't look bad, and I saw no contamination or indicators or any problem in that canister. But, I had a new 'spare', so I replaced it.
After all this, I grabbed a hose and test ran the engine. And, as fate would have it, it fired up and seemed to idle smoothly on all 4 cylinders while on the trailer. I even 'revved' the engine and it seemed to run up well. I don't 'over-rev' while un-loaded, so I only spin a free-revving motor to about 3K RPM, but at that level it held on to running smoothly, so from all appearances my problem may be 'fixed'. BUT...... I don't think so! I'll know later after I launch the boat and try to run it some. I also bought a plastic bottle of that Yamaha 'Ring-Free' fuel additive? Like $68 for a quart of the stuff!!!???!!! Really? Was I a sucker, or what!! Anyway, I'm going to mix up a 'shock' batch of that stuff and add it to my gas tank. I guess it can't hurt.
So, what I'm looking for here are any other ideas or suggestions regarding the problem as described and the repair attempts I've noted above. From where I sit, I didn't really 'fix' anything! Given the VST was full of gas, I'm incline to think that anything up to that point was probably OK, meaning the small in-line filter was NOT clogged, and the lift-pump was functioning normally as it should. Had I found some indication of contamination within the VST, or a non-functioning HP pump, again, I might have felt better about maybe having ID'd the problem. But, as stated, this looked like a brand new component, right down to the internal screen-filter on the end of the HP Pump itself. So, I'm baffled! I'm also a bit 'miffed' that an reasonably new motor with less than 125 hours would exhibit this kind of problem. But, Cest La Vie!
Any help or suggestions would be greatly appreciated. Many thanks! Tom D.