I started the engine yesterday, exhaust didn't sound right. Sounded mostly like only air is coming out of the exhaust, shut the engine down. Confirmed thru valve was opened, had my wife start the engine again. Didn't see any flow in the strainer, shut it down again. After looking around, thought impeller is the weakest part. A little history: I changed the impeller for the 1st time at 700 hrs, looked like new. Now have nearly 1400 hrs, figured not a bad idea, this one had been used for 5 years.
I got to admit, it is a pain getting the old impeller out, need the right tools (see below). Once I got it out, inspected the 5-yr old impeller--looks like new. Put a new one back in anyway. Also a pain putting the new one in. Once installed, started the engine, sounds normal.
Lessons I personally learned, worth sharing: These Yanmar impellers are fantastic. BUT STILL NEED TO KEEP A NEW SPARE. Pretty sure could have got a few more years. Great to have the right tools. At 1st started with 6" or so pliers to pull the old impeller. Since that didn't work out too well, dug in the tool box & got a small needle nose pliers. After about 10 tugs, old one came right out. To install the new one, coated the blades with dish soap. Tried compressing the blades by hand, pretty tough with all that soap. A call to Garry indicated should have put a hose clamp around it to compress the blades. Was too late for me as now about 1/2 way in, but having a tough job getting it all in the pump. Thought turning the engine would align the blades, so pulled the engine-stop & cranked about 1/2 second. Then new impeller went in quite easily. Put the plate back on & everything sounded normal.
Big question is why did I need to replace an impeller that looks like new? I'm not sure why changing it helped. Only thought I have is should have rev ed up the RPM to 2500 or so in case lost prime. Pretty sure that would have solved my issue. Another lesson is leaving 1 hour later for a 35 mile trip allowed me to sail more than leaving at 11 AM.
