You know I do have two three way valves to select which filter is used. I don't think that is a problem as once the engine runs there is no hesitation, which with a vacuum leak would I think cause momentary dips in the engine speed.
I have been meaning to rework that as its not at all easy to get to the valves except by removing everything from the lazzerette and climbing inside. A bit too fussy in my mind when away from a dock
On the engine catching. Well when it starts its running on one cylinder right away, I then can hear the other two cylinders pick up the load. That is there is a change in engine speed and sound as each of the other two cylinders come on line.
I still have not discounted that it might be rings/ piston either. Just saving the best for last as it were. I truly am not looking forward to pulling the engine out and taking it apart. So not on my list of fun things to do.
Though I have actually rebuild
a number of engines, from VW or motorcycle to LBC's. Plus assisted / watch my dad do that too from about age 6 up. weird girl I know...
Hum, The yanmar
operation manual, does state to put the throttle at 50% at start. Though for the first 5 years I had the boat, it would start up without any additional throttle. Maybe its just broken in now......
I think I might know someone with a diesel compression gauge, Waiting on getting that for a compression check...
I cleaned the air filter last week too. So air side and fuel to the hp pump has been checked