I have a 2005 Hunter 38 with a 40 hp Yanmar. She runs beautifully, well until recently. I was cruising along at 2800 rpms against a current approaching a draw bridge (thank goodness the current was against, me this time) and the engine cut out with out any alarms. Long story short, got her started after throwing the hook and got back to the slip, and then changed out both fuel filters thinking there was sediment build up. The next day she ran great until I put the rpms up to 2600-2800rpms and she began to lose power, if I powered down she would hold steady. After filling the tank, mind you there was 25 gallons of fuel in the tank already, she performed with no problems. So I concluded that there must have been air in the fuel lines and then worked itself out. Unfortunately this past weekend the same thing happened at the higher rpms, so we limped in, of course against the current at 2000 rpms and finally made it to my slip. Any thoughts? I'm thinking an air leak in one of the fuel lines, and if so, how do you track that down?
40hp yanmar engine cutting out at higher rpms, no warning alarms
- Thread starter SWagner
- Start date
fuel or air is being limited or eliminated. How much water is shipped over in the cooling circuit?? Temps when things fail...might be the fuel filter on the side of the block...when was it last changed? Elbow or exhaust restriction...does the exhaust change color or sound. Enough air in the engine room, blower working and so on. Fuel shutoff lever(s) fully OFF?
How long at high RPM before it quits? When was the fuel pickup last cleaned...it could be partially clogged and goes completely clogged with more fuel being requested..
I would look at these before going to air leaks...most air issues will show at lower RPM as well as higher.
How long at high RPM before it quits? When was the fuel pickup last cleaned...it could be partially clogged and goes completely clogged with more fuel being requested..
I would look at these before going to air leaks...most air issues will show at lower RPM as well as higher.
Thanks for the feedback. Just changed both fuel filters two weeks ago after the first event. The exhaust seems normal. I used the blower during the summer when it was hot, but not lately since it's been cooler. Actually I didn't use the blower last summer and all was well.
I was running at 2800rpms for about 10 minutes before losing power. I bought the vessel two Decembers ago, so not sure when or if the fuel pickup was cleaned, good tip and will look into that.
I was running at 2800rpms for about 10 minutes before losing power. I bought the vessel two Decembers ago, so not sure when or if the fuel pickup was cleaned, good tip and will look into that.
The fuel pick up is a prime suspect. There is often a screen on the pickup to prevent crud from reaching the filters, this is one of those good ideas on paper, but not so much in real life. Remove the pick up tube, and remove the screen and place the screen in a suitable garbage container.
If the screen is clogged it means the tank has sediment in it that should be removed and the tank cleaned. If there is an inspection port shine a light down in there to see what it looks like. Or draw some fuel from the bottom of the tank and let it sit in a glass jar for a little while to see what settles out of the fuel.
If the screen is clogged it means the tank has sediment in it that should be removed and the tank cleaned. If there is an inspection port shine a light down in there to see what it looks like. Or draw some fuel from the bottom of the tank and let it sit in a glass jar for a little while to see what settles out of the fuel.
If you’ve plugged a filter or two, be sure and check the filter hidden in the lift pump. I agree primary to check the vent.
Les
Les
90% of the time problems are fuel related. Usually where there is an air leak you will also find a fuel leak. When the engine is running air gets sucked in and when the engine is turned off fuel will leak out. Clean and dry all the connectors at the lines, filters, bleed screws and lift pump and then see where you may find a fuel leak after running the engine. A restriction in the fuel flow may also cause fuel starvation at higher RPM. Sediment in the tank can partially block the screen in the tank's pick-up tube and cause a blockage. I blow compressed air through the fuel line back into the tank to clear any obstructions but in order not to damage the tank the fuel filler cap must be removed. In extreme cases the fuel would need to be polished and the tank cleaned. Pick up tube blockages usually manifest themselves in rough seas as the fuel sloshes around the tank and stirs sediment. Drain the water separator and see how much water you get out, excessive water in the fuel can also cause problems. If the fuel pump were to have an internal leak fuel could leak into the engine's crankcase, check the level and consistency of the oil to rule out a leaking pump. I once had a sticking high pressure pump but that would be a rare occurrence. If you asked me to take a guess I would say a partial blockage in the pick up tube.
Thought I'd let you all know that the screen on the fuel pick up line from the tank was covered in slug. Cleaning it took care of the problem. Will have the fuel polished over the winter. Happy sailing!
It takes water to grow sludge in fuel, so lube and or replace the O ring in the fuel filler cap. Also use a biocide, but mostly eliminate the water. Some water probably remains in the tank below the fuel pick up, so doesn't make it to the water separator at the primary filter. That's why you should use a biocide. Water can also come from condensation, or come in with bad fuel, but most comes from the fuel filler, around the seal.