So I've now taken some more advice from a couple of Yanmar dealers and changed the filters and had a further think and this is where I am now :
The concerns that I had were :-
a) I couldn't hear the turbo operating any more.
b) I wasn't getting the speed I expected even with a pretty clean hull
c) I seemed to be getting a little more smoke than I expect
I cleaned the filters with no change in performance or smoke.
I checked the speeds at various engine RPM's and double checked that the tacho was accurate with a separate photo
tach. Here are the results :-
1,500 2.9 Kn
2,000 4.2 Kn
2,500 5.4 Kn
2,800 5.8 Kn
3,000 6.0 Kn
3,200 6.2 Kn
I was able to increase the RPM to 4,200 before I checkened out and reduced the revs.
According to the manual maximum power for the 4JH3TE comes at 3,700 RPM.
I'm using a 3 blade
So my question now is .... does anyone think I'm underpitched on the prop or should I just be operating the engine at higher RPM's ?
I generally cruise
at 2,800 RPM, but the above would suggest that 3,200 or even higher would be perfectly OK.
Also ... I managed to get some genuine turbowash from a Yanmar dealer. Seems that they now package it in 150ml packs (~$10), but the packaging instructions are entirely in Japanese. I'll have a go with this later.