I couldn't find any thread about this...
I have owned my Hunter
466 (2003 model) since 2006. I'm still learning
all the ins and outs of the powered aspect of a sailboat. I have the engine
sort of figured out but have tended to neglect the shaft and prop aside from cleaning
off and keeping the anodes in working order.
I had the engine's injectors serviced 2 years ago (replaced 2 and cleaned the others) because the engine
was running very smokey. At that time I was told to run the engine at higher RPM's to keep it happy... I had been running it at about 2500-3000 RPM
thinking that was ideal. So I ran it at max throttle (3100 RPM).
I recently hauled out the boat
to bottom coat and was told by the mechanic
who replaced the cutlass bearing (different from the guys who serviced the engine 2 years ago) after doing his sea trial that my propeller
is likely "over-pitched" as the engine (Yanmar 4JH3-TE) with a Kanzaki
(gear ratio 2.63) is not running at the right RPM
at full throttle - should be 3900 RPM and the most I can get is about 3100 RPM. Of course he told me this AFTER we were back in the water
. I explained that the prop was set at the same pitch
as when I got the boat
and assumed it was correct. He said that sailboat owners tend to over-pitch their props thinking they are saving fuel
running at lower RPMs (as I was doing), but in fact are just wasting fuel
out the exhaust
(something to do with the turbo charging). I decided to look into this.
My prop is a MaxProp 3 Blade
fast (V.P.). I scared up the original operator's manual and found that the PO had set the pitch
at 25 degrees, which for my 18" 3 blade
prop corresponds to a pitch of about 14" based on their table. I noticed from the PO's notes that he used the wrong gear
ratio for the calculation (he used 2.83 rather than 2.63).
From the vicprop.com site I calculated that for my hull
shape (LOA 40', beam 14' and draft
of 3') and displacement
(27,000 lbs) , engine power rating of 75 HP that my 18" prop should be set at about 22" for a desired hull speed
of 8.5 knots.
On the weekend I went down with my mask on to check the prop's setting and sure enough it was set at 25 degrees (RIGHT). I tried to reset the pitch... easy enough to do with that prop model if the mechanicals of the pitch adjustment collar weren't gummed up.. but could only manage to slip the collar up but not adjust anything... so I just had to leave it as is.
So my question to the audience is this: How worried should I be about this? Should I be hauling out and cleaning
up the prop and adjusting it to 22 degrees, or do I just live with it until I haul again in 2 years time (haul out is about $800). And If I live with it as is for now, should I be lowering my engine RPM.. as I right now tend to run it a full throttle (3100 RPM). Am I damaging the engine running it at 3100 RPM? Note that it doesn't overheat or sound weird.
Thanks for any input..