My recent history with Yamaha’s is chronicled in this thread. http://forums.iboats.com/showthread.php?t=525616 It has nothing to do with this problem, other than to give credence that Yamaha’s don’t like me!
The following is LONG, but I wanted to ensure that I included a good history and details so that, hopefully, one of you can guide me in the right direction. …here we go…
I am having an idling and loss of power issue. The motor is a 2003 Yamaha F90TLRB (carburetor). I purchased this engine used two months ago from a dealer (is was on consignment…owner purchased a new lighter weight engine). It had 45 hours on it. The engine is super clean and was maintained by the dealer. After I mounted the engine (pontoon boat) I changed the oil and filter (oil had been drained for transport). I cleaned the “external” fuel tank (it had a 2 stroke mix in it), washed and dried it. Replaced the fuel line, bulb, remote spin-on filter with clear bottom, and new fuel line from the filter directly to the engine filter (which I also cleaned). The tank was filled will fresh 100% gas (no ethanol), and that is what I have used since.
The engine performed excellent with no issues. WOT was 5,600 – 5,700 RPM. I had lowered the idle RPM to 600-700 (at 800 trolling speed was too fast). At approximately 60 hours I had noticed it had a very slight miss at idle while running on the hose. Could not tell it when running in the water. I decided to pull the plugs and take a look.
Plug #1 looked normal. #2 looked like it was running a little warm, but still ok (negative electrode was a little light colored). #3 had a little crusty white ash on it. #4 was similar to #3 but had a white chunk (ash I assume) between the center electrode and body. I replaced the plugs using the recommended plug and gap setting.
The miss at idle (on the hose) was gone and it was much smoother. In the water my WOT was now 6,000 – 6,100 RPM. Fantastic. I used it about 3 hours with a combination of idle, midrange and WOT. No problems. On the next trip out, things changed. It developed a slight miss at idle and on two occasions at near WOT the engine ran rough, slowed down and then returned to normal.
Following this event, I checked the entire fuel system. All the new fuel components only had 15 hours on them. No lines were pinched or occluded. I removed the fuel hose from the internal/engine filter to see if it would free flow. No problems there. I installed a barbed splice and connected a piece of clear tubing between the end of the fuel line and the internal/engine filter (looking for air bubbles). I unplugged the hose from the tank while the engine was running and with a few seconds it had sucked the bulb flat. I let it continue to run until the engine was starving for fuel; no air bubbles were noted in the clear hose. Hooking it back up to the tank, the bulb immediately filled. I removed the piece of clear hose and reconnected everything. I feel confident there are no fuel delivery issues between the tank and the fuel pump.
On the next trip, we had about 45 minutes of fast idle (long No Wake Zone). The next 2 hours were in open water and I pushed her to WOT for a couple of minutes and then backed off to about 5,300 RPM. After about 20 minutes I noticed a slight miss. It continued to get worse. Over the next 1.5 hours the miss was intermittent. Slowing down to a fast idle the miss cleared. Accelerating back to WOT only delivered 5,400 – 5,500 RPM. After a couple of minutes it started missing again and would then sound like it was dropping a cylinder completely. I did the slow down speed up cycle several times. It continued to get worse. I was able to find a spot around 3,500 RPM where it ran fairly smooth, with ONLY an occasional miss. We arrived back at the boat ramp.
When I cranked the engine to put the boat on the trailer, it was very difficult to start. Back home, on the hose, it idled very rough.
This morning I removed the plugs and much to my dismay, I found a mess. #1 was normal. #2 looked like it was running a little warm. #3 was covered in thick crusty white ash. #4 was similar to #3 but the gap between the center electrode and the plug body will filled with the ash. Please see pictures. I went back through the fuel system, visually, and still feel certain that I do not have a fuel delivery problem to the fuel pump. I also unbolted the fuel pump and squeezed the bulb hard to see if I had fuel leakage on the back side (possible diaphragm issue). No problems there, reinstalled the pump.
I have seen a lot of “hot” plugs from a slight run-lean condition, but honestly I don’t have a clue about all this white ash! My next step is to pull the carbs and clean them. The next step, after that, is a bullet. Someone is going to have to shoot me or the motor…because one of needs some relief!
I welcome your ASAP input, suggestions and questions. Thanks!
The following is LONG, but I wanted to ensure that I included a good history and details so that, hopefully, one of you can guide me in the right direction. …here we go…
I am having an idling and loss of power issue. The motor is a 2003 Yamaha F90TLRB (carburetor). I purchased this engine used two months ago from a dealer (is was on consignment…owner purchased a new lighter weight engine). It had 45 hours on it. The engine is super clean and was maintained by the dealer. After I mounted the engine (pontoon boat) I changed the oil and filter (oil had been drained for transport). I cleaned the “external” fuel tank (it had a 2 stroke mix in it), washed and dried it. Replaced the fuel line, bulb, remote spin-on filter with clear bottom, and new fuel line from the filter directly to the engine filter (which I also cleaned). The tank was filled will fresh 100% gas (no ethanol), and that is what I have used since.
The engine performed excellent with no issues. WOT was 5,600 – 5,700 RPM. I had lowered the idle RPM to 600-700 (at 800 trolling speed was too fast). At approximately 60 hours I had noticed it had a very slight miss at idle while running on the hose. Could not tell it when running in the water. I decided to pull the plugs and take a look.
Plug #1 looked normal. #2 looked like it was running a little warm, but still ok (negative electrode was a little light colored). #3 had a little crusty white ash on it. #4 was similar to #3 but had a white chunk (ash I assume) between the center electrode and body. I replaced the plugs using the recommended plug and gap setting.
The miss at idle (on the hose) was gone and it was much smoother. In the water my WOT was now 6,000 – 6,100 RPM. Fantastic. I used it about 3 hours with a combination of idle, midrange and WOT. No problems. On the next trip out, things changed. It developed a slight miss at idle and on two occasions at near WOT the engine ran rough, slowed down and then returned to normal.
Following this event, I checked the entire fuel system. All the new fuel components only had 15 hours on them. No lines were pinched or occluded. I removed the fuel hose from the internal/engine filter to see if it would free flow. No problems there. I installed a barbed splice and connected a piece of clear tubing between the end of the fuel line and the internal/engine filter (looking for air bubbles). I unplugged the hose from the tank while the engine was running and with a few seconds it had sucked the bulb flat. I let it continue to run until the engine was starving for fuel; no air bubbles were noted in the clear hose. Hooking it back up to the tank, the bulb immediately filled. I removed the piece of clear hose and reconnected everything. I feel confident there are no fuel delivery issues between the tank and the fuel pump.
On the next trip, we had about 45 minutes of fast idle (long No Wake Zone). The next 2 hours were in open water and I pushed her to WOT for a couple of minutes and then backed off to about 5,300 RPM. After about 20 minutes I noticed a slight miss. It continued to get worse. Over the next 1.5 hours the miss was intermittent. Slowing down to a fast idle the miss cleared. Accelerating back to WOT only delivered 5,400 – 5,500 RPM. After a couple of minutes it started missing again and would then sound like it was dropping a cylinder completely. I did the slow down speed up cycle several times. It continued to get worse. I was able to find a spot around 3,500 RPM where it ran fairly smooth, with ONLY an occasional miss. We arrived back at the boat ramp.
When I cranked the engine to put the boat on the trailer, it was very difficult to start. Back home, on the hose, it idled very rough.
This morning I removed the plugs and much to my dismay, I found a mess. #1 was normal. #2 looked like it was running a little warm. #3 was covered in thick crusty white ash. #4 was similar to #3 but the gap between the center electrode and the plug body will filled with the ash. Please see pictures. I went back through the fuel system, visually, and still feel certain that I do not have a fuel delivery problem to the fuel pump. I also unbolted the fuel pump and squeezed the bulb hard to see if I had fuel leakage on the back side (possible diaphragm issue). No problems there, reinstalled the pump.
I have seen a lot of “hot” plugs from a slight run-lean condition, but honestly I don’t have a clue about all this white ash! My next step is to pull the carbs and clean them. The next step, after that, is a bullet. Someone is going to have to shoot me or the motor…because one of needs some relief!
I welcome your ASAP input, suggestions and questions. Thanks!