[C320-list] Low speed under Load

[Marek Fluder]

Jeff,

I have also Yanmar 3YM30 with fixed 3 blade 15R12 prop and found that my
speeds are similar to Don's:
1500 - 4 knots
2000 - 5 knots
2500 - 6 knots
Kanzaki transmission with 2.62 gear ratio.
Am I over-pitched as well ?

Marek
#1028



On Mon, Jul 13, 2015 at 3:26 PM, Jeff Hare <Catalina at thehares.com> wrote:

> Well...
>
> First, to be getting 5kts at 2000 rpm means you're well over pitched
> regardless of which prop you have.  So, you'll be building up carbon in the
> elbow like crazy this way.  Even if it seems ok it isn't.  So I'm guessing
> your exhaust elbow is probably clogged unless you can rev to 3800 RPM
> easily
> in neutral.  Since your diver says your prop is clean, there are really
> only
> a few things I can think of that can keep you from getting over 2800 rpm
> under way.
>
> 1:  Over pitched prop
> 2:  Clogged elbow
> 3:  Dirty prop  (ruled this one out)
> 4:  Dirty Primary or Secondary fuel filter
>
> I think #1 caused #2.
>
> -Jeff Hare
> #809
>
> -----Original Message-----
> From: C320-list [mailto:c320-list-bounces at lists.catalina320.com] On Behalf
> Of Donald Lawson
> Sent: Monday, July 13, 2015 2:33 PM
> To: C320-List at Catalina320.com
> Subject: [C320-list] Low speed under Load
>
> All
> I have 2004 320 with a Yanmar 3YM30 fitted with a 15x9 MaxProp by PO.
> Everything has worked well for 3 years. At last spring haulout I had the
> prop serviced and bottom painted. Boat worked great. Recently I get 5 knots
> at 2000 rpm, which is normal.  However there is no increase in boat speed
> past 5 knots up to 2800rpm.  Cant' get above 2800 rpm. Rpm to 3000+ easily
> in neutral.  No visible exhaust  at 2000rpm.
> Skipper says some minor black smoke at 2800 rpm. Seemed like a mist to me.
> Recently serviced.  Got fuel and air OK. Had diver check MaxProp.  Seems
> OK.
> Diver cleans bottom and prop once a month.
> Anyone had a transmission trouble with a Yanmar? Starting to grasp at
> straws.
>
> Don Lawson
> "Mandolin Wind"
> Ventura, CA
>
>