[C320-list] Low speed under Load

[Arthur Miller]

Jeff, 
I have 2 blade max. Prop. And get similar rpm/speeds.  I generally cruise at 2650rpm
Which in still waters is 6+ Knts.
Art. #680

Sent from my iPad

> On Jul 14, 2015, at 9:25 AM, Marek Fluder <marekf at gmail.com> wrote:
> 
> 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
>> 
>>