Gori Prop Query

[pj]

This is a query for Zanshin and any other 49DS owners with gori's and the 4JH3-TE (75hp) engine.
I having a problem (in normal drive) getting enough thrust without over-reving the engine. This points to insufficient pitch. The Gori fitted to my 49DS is a 20x13 3RH. Could you let me know the dimensions are for the Gori's on your 49DS's?
Many thanks
PJ

[Zanshin]

PJ - I'm far away from the boat so cannot check the prop, and the original invoice for the boat doesn't specify the model of the Gori propeller (but I have some close-up pictures of my Gori, if that is any help). I don't motor much, and usually use the overdrive setting rather than the normal one. If I were to guesstimate, I'd say that I do about 7 knots at 2800RPM.

What speed at what RPM are you getting?

www.sv-zanshin.com/Gori.html

[pj]

Hi Zanshin- Thanks for responding. Unfortunately the photos don't assist. The only way of knowing is having the specs from purchase.
My overdrive performance is spectacular (I think) 6 kt @ 1900 rpm yeilding 2.3 lt/hr (0.6 US gal). THe problem is in normal drive the engine will rev through 4000 rpm with ease ( would go as high as 4500 !). the 75 hp Yanmar is has a max rev spec of 3800 so if the pitch is correct theoretically max hull speed (8 to 9 KT) should be achieved at around 3500rpm.
Maybe Gori have been under-specifying the props after some gearbox failures resulting from overloading in overdrive?

[Zanshin]

I don't believe that Gori would intentionally pitch the prop lower, I would think that the overloading in overdrive would overheat the engine (as happened to me once) rather than stressing the gearbox. Certainly getting above 3800 rpm in normal conditions is indicative of problems. I haven't tried to see what my maximum RPMs are for my boat (although 2200RPM in overdrive in medium seas overheated my engine, I was at 2100 for a lengthy period before I upped the revs so believe that that is the limit in overdrive on my boat). I intend on installing a pyrometer to measure the exhaust gas temperature so that I won't overload the engine again.

[rhb]

I'm just curious - have you checked to make sure your tachometer is accurately displaying engine speed?

4500 rpm is incredibly high for a Yanmar of any kind.

When the tach says 4500 is the boat performing as you would expect it to at normal max rpms?

If there isn't a lot of excessive vibration nor smoke or other symptoms of an engine about to self destruct I'd be inclined to validate the tach before suspecting the prop.

I'm not a diesel expert by any means so take my input with a bit of skepticism.

[pj]

Thanks rhb -the taco is fine. We haven't gone to 4500 but it feels as though it would which points to lack of pitch. No smoke or overhaeting! I'm surprised that Zan has had overheating problems - I motorsailed back from Vanuatu a couple of trips ago for 4 days without an issue.

[Zanshin]

pj - were you motorsailing upwind at over 2200 rpm in "overdrive" mode in not-too-calm seas - that's what did it for me)

[pj]

Zanshin, No hardly any wind and flat seas - kept it at around 1900 rpm and 6 kts in case I had to motor 1100 nm! So no load on engine and gearbox.

[Zanshin]

In my case the extra 100RPM pushed my engine over the edge, at 2100 I had been motorsailing for several hours (I wanted to get into Falmouth Harbour in Antigua before sunset) in choppy seas without a problem, but then I upped the RPMs a bit when I slipped behind my time schedule and within minutes the engine alarm went off.
I love the Gori "overdrive" and your example is a perfect illustration of where the Gori shines.

[Janissah]

I know this is an old thread, but i need to point out that with the overdrive on the turbo on the engine does not cut in, leaving one with a coked turbo. This happened to me. I get 2000 revs and the turbo cuts in at 2200.

The overdrive is great but one needs to give it a rest after a while. the engine does overheat when motoring for long periods of time with the overdrive on. Alarm goes off but stops once engine revs are lowered.

I have a Sun Odyssey 45 with the Yanmar 75hp engine.