Give DH Porter a call (02) 9890 1766. They were very helpful in working out the size of the prop
needed for my boat. They'll want to know engine and gearbox details, so be prepared.

Use Porters. He is a great bloke and provides excellent advice.
However, as others have said know your engine power, gearbox reduction ratio, currrnt prop pitch and diameter and if it allows the engine to reach full revs or if it over revs.
without the revs he can still give good pointers on your needs.

samsturdy said..
Give DH Porter a call (02) 9890 1766. They were very helpful in working out the size of the prop
needed for my boat. They'll want to know engine and gearbox details, so be prepared.

You Wil also need waterline and how wide.

Easy to get wrong
local marine engineers in Melbourne replaced my prop but overpitched to b...
couldn't get over 2500 revs
bukh 28 hp
Cavalier 32

miscalculated
astral replaced with less pitch,now fine

Jode5 said..

TKNick said..
DH Porter sized the existing prop, a 17 x 11R, for the existing Yanmar 3QM30 33HP at 2800 and 30hp at 2600 continuous. The gear box is a 2.14 : 1 ratio. I always felt the boat was under propped as the engine would rev up 3200 at WOT with the yacht only reaching 6.2 knots on flat water with no tidal flow. This was on a tired 34 year old engine with poor compression on no2 cylinder. I am suspicious that the gearbox is actually a 3:1 and incorrectly plated as I should be getting a cruising speed of 6 knots at 2200 rpm.
The new engine I am looking at is a Vetus M4.35 (Mitsubishi S4L2 1.758L) that produces 33hp at 3000rpm. The Calculator on VicProp gives 16.4 X 9.7 while Michigan Wheel Prop Calculator gives 18 x 10. If I do the calculation on a continuous max revs of 2750 (my guess as none stated on engine specs) Vic Prop gives 17.3 x 10.6.
I am hoping to get away with the existing prop as it is relatively new. At worst I might be slightly over propped. Searching the web it seems many deliberately over prop to get a better speed at slower rpm; possibly doing damage to their engines. Some yachts though have had this setup for many years with the engines still going strong.

A great choice of motors. I put a Vetus M4.35 into one of my previous boats and was the best motor I have ever had. Being 4 cylinder they run as smooth as silk. I don't believe over pitching it all that bad as most people don't run at full revs for long periods of time and when running at low revs it will put a little more load on the motor which is good for the motor. I would try you existing prop if it is close to the required pitch. By using the existing prop you will get a good idea how much more or less pitch you require. From experience prop calculators don't usually get it exactly correct. Porters did the repitching of my prop and it is still not a 100% correct. When I replace my prop I will be replacing it with a MaxProp adjustable pitch 4 blade feathering propeller.

A great thing about Vetus marine engines is the 5 year warranty. The engine is a Mitsubishi S4L2 so the non marinized parts are readily available and reasonably priced. Ryco oil (Z456) and fuel filters (Z533) can be used; isn't Google great! Interestingly Vetus use the same S4L2 engine for the M4.35, M4.45 and M4.56(Turbo). All 3 have the same capacity 1758 cm3. On the spec sheet the only difference I can see is the injection timing.
I will see how the existing prop goes and if need be I will get Porters to de pitch the prop. Luckily having 2 keels gives me easy 'low tide' access to remove the prop.

someday said..
To get a rough estimate I place a straight edge across the chart on p.406 of "The Nature of Boats" by Dave Gerr which is also reproduced on p. 200 of "Nigel Calder's Cruising Handbook" and neither the 2.0:1 or 2.5:1 ratios of the Vetus M4.35 TMC60P standard gearbox match a 17" 3 blade propeller. You could try it yourself if you have either of those books. The propeller rotation speed is also different to the Yanmar 3QM30.

A new engine would be nice. The cylinder sleeves, pistons, rings and a few other parts are available for the obsolete Yanmar 3QM30 here:

www.hoyetractor.com/CTGY/3QM30.htm

Thanks for the link 'Someday'. The motor blew a head gasket and a little seawater got into no2 cylinder. My intention is to remove the no 2 cylinder and either hone or replace the liner; a new set of rings and recondition the head. I will then sell the 3QM 30 as a working engine once tested. The QM series motors are well regarded for their robustness.

The two engines produce the same HP at the same RPM so I hopefully will be alright. Vetus Australia sell the m4.35 with a ZF 12M transmission 2.14:1 which is the same ratio as the Yanmar. The QM Series Service Manual states the best propeller size to be an 18x12 RH. Warlock seemed under propped with the 17x11 going past 3000 rpm WOT on flat water.

I have now installed the new Vetus M4.35 and have put 17 hours on the engine after a trip to Ulladulla to slip the yacht.
I am very pleased with the engine and how the boat now performs. I decided to keep the existing prop that was slightly over size by 2 inch of pitch according to some prop calculators. The max rated hp is 33 at 3000 rpm. I managed to get to 2900 and attained 7.4 knots (hull speed) in flat water with no tidal flow. It was how the engine performed at sea that really impressed me. Last Monday punching into a 16 Knot southerly with 1.5 - 2 meter SE swell I was attaining 5.2 knots at 2000 rpm. When I left Ulladulla early yesterday with a 4 knot SW and a 1 - 1.5 SW swell 1900 rpm was pushing Warlock along at 6 knots; opening up to 2300 for about 5 minutes gave me 7.4 knots. Navigating up the Crookhaven River and Berry's Canal with a out going mid tide I was getting 6 knots at 2000 rpm The old Yanmar 3 QM30 would only get to 4.5 knots at 2300 rpm in the same circumstance.
This begs a question; why would the new motor be attaining a much greater speed at the same rpm when the engines have near identical gear ratio with the same 17 x 11 prop and with prop plus hull clean Am I missing something

Hp would be different even though both rated at 30 hp.
Old probably at the flywheel new at the shaft.

TKNick said..

Jolene said..

TKNick said..
I have now installed the new Vetus M4.35 and have put 17 hours on the engine after a trip to Ulladulla to slip the yacht.
I am very pleased with the engine and how the boat now performs. I decided to keep the existing prop that was slightly over size by 2 inch of pitch according to some prop calculators. The max rated hp is 33 at 3000 rpm. I managed to get to 2900 and attained 7.4 knots (hull speed) in flat water with no tidal flow. It was how the engine performed at sea that really impressed me. Last Monday punching into a 16 Knot southerly with 1.5 - 2 meter SE swell I was attaining 5.2 knots at 2000 rpm. When I left Ulladulla early yesterday with a 4 knot SW and a 1 - 1.5 SW swell 1900 rpm was pushing Warlock along at 6 knots; opening up to 2300 for about 5 minutes gave me 7.4 knots. Navigating up the Crookhaven River and Berry's Canal with a out going mid tide I was getting 6 knots at 2000 rpm The old Yanmar 3 QM30 would only get to 4.5 knots at 2300 rpm in the same circumstance.
This begs a question; why would the new motor be attaining a much greater speed at the same rpm when the engines have near identical gear ratio with the same 17 x 11 prop and with prop plus hull clean Am I missing something

Maybe one or both of the tachometers are reading incorrectly.

That might explain it. I will have to get the new enginesengines tacho checked, though the idle speed of 840 rpm feels about right.

or the friction drive in the old Yanmar gearbox is slipping

A good result in the end TKnick!
My VP D1-30 was always disappointingly slow, after checking the Tach it was well out, so the previous owner was running at what he thought was near max RPM but was only turning at 2400
my boat is 37 foot with probably more beam than yours and 7 tonnes dry. An the speeds are similar with sail drive and two blade folding
17-12 Flexofold
cheers Richard

Seebreasy73 said..

TKNick said..
I have now installed the new Vetus M4.35 and have put 17 hours on the engine after a trip to Ulladulla to slip the yacht.
I am very pleased with the engine and how the boat now performs. I decided to keep the existing prop that was slightly over size by 2 inch of pitch according to some prop calculators. The max rated hp is 33 at 3000 rpm. I managed to get to 2900 and attained 7.4 knots (hull speed) in flat water with no tidal flow. It was how the engine performed at sea that really impressed me. Last Monday punching into a 16 Knot southerly with 1.5 - 2 meter SE swell I was attaining 5.2 knots at 2000 rpm. When I left Ulladulla early yesterday with a 4 knot SW and a 1 - 1.5 SW swell 1900 rpm was pushing Warlock along at 6 knots; opening up to 2300 for about 5 minutes gave me 7.4 knots. Navigating up the Crookhaven River and Berry's Canal with a out going mid tide I was getting 6 knots at 2000 rpm The old Yanmar 3 QM30 would only get to 4.5 knots at 2300 rpm in the same circumstance.
This begs a question; why would the new motor be attaining a much greater speed at the same rpm when the engines have near identical gear ratio with the same 17 x 11 prop and with prop plus hull clean Am I missing something

I may need to replace the 16HP Yanmar on the Compass and I have heard people mentioning the Vetus M2 for that. However, I may step up to the M3 with the extra 10 HP.

Have you installed the engine yourself? How easy was to pair the new engine to the existing prop shaft? And how does fuel consumption compare to your old yanmar? Finally, the Vetus seem to run a bit rougher than a yanmar (just looking at some videos on youtube), have you noticed more vibrations through the yacht at all?

Yes I did the installation myself. It was rather straightforward. Make a plywood template of the new engine and fit your mounts to this. It will show you any bed modifications you need to do. I had to fit a new shaft coupling as I had to go from 5 to 4 inches. Don't over size the new engine as it won't ever work hard enough for a long life.
Also take into consideration the gearbox ratio and prop size or else you might have to change all this.
Vetus are marinized mitsubishi diesels. I found mine to be much smoother and quieter than the Yanmar 3QM30. Some areas where the Vetus is very good is things like a self priming electric fuel pump, epoxy engine enamel paint, and a bronze exhaust mixer elbow. The marinization seems to be done very well. Parts are readily available.

The Vetus Diesel just has standard non electronic injectors. Delivery was about 10 days from Brisbane to Shell Cove. Call Wayne at the Bosuns Locker Chandlery (Gold Coast) on 07 5595 1911. They are an agent for Vetus but don't list the engines on there web site anymore. Wayne should be able to get you an engine though at a good price. McIntyre Equipment in Brisbane also sell them. Vetus Maxwell are also located Brisbane and I have found them excellent to deal with.