which prop is right for my boat

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mj81

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Hi, does anybody out there have a Volvo Penta D1-30 with a MS10A-B gearbox? I am finding it very difficult to get a firm answer on what the gearbox ratio is and am getting conflicting answers from different dealers. The problem I have it that at about 2500rpm on the engine in calm sheltered conditions I am only getting 4-4.5 knots and I can over rev the engine. This is what has led me to start investigating the prop further. Any help/suggestions on the gearbox ratio and what is the right prop for my westerly falcon 34 would be very helpful
 
On my Volvo gearbox on my Westerly Storm (can't remember the model) there's a plate on the rear with the serial number on it AND the gearbox ratio. It's difficult to see, but possible.
 
You could measure the overall gearing with a dab of tippex on the crankshaft pulley and a dab on the prop shaft. Turn the pulley one turn with a spanner and get someone to watch the prop shaft. Release the compressor or do it very slowly so as not to start the engine! :(

Richard
 
Think you will find it is about 2.3:1 or maybe 2.4 to give a shaft speed of 14-1500rpm. Your prop is too "big" - either too big diameter or too much pitch. Calculations give 17*13 2 blade 0r 16*13 3 blade. Either will allow you to get close to 3200 rpm and just over 7 knots. These assume standard type fixed props and folding or feathering may be different.
 
Tranona I don't understand why,but the way I read this manual,it is saying you can operate the gearbox in LH or RH as forward.
If this is so,then one direction is 2.35 & opposite is 2.70 -or am I wrong?
Please see page 15 of this PDF. Also,there should be a tag on top of gearbox,stbd side of center near dipstick-from pics online.
http://www.lundskovs.dk/bavaria/manualer/Volvo/volvo_penta_installation_manual.pdf

Edit-The Di 30 rated 27HP ~3000RPM
My old VP 2003 28HP with MS2B is eqpd with a 17x14 LH 3blade & it's a bit heavy-peaks at 2600RPM.WOT & 3400 in N. A 17x12 would probably be about right to peak at 31-3200,but it's been that way for 2100 hrs,handles like a power boat & cruises 6.9 kts @ 2400

Cheers/ Len
 
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Looks like it. The MS10 seems to be available with 2 forward ratios (2.35 and 2.7) but both reverse are 2.7, but either can be used for both forward and reverse. in which case the OP does need to check that he is running the 2.35 - ie with a RH prop for my calculations to be correct.

Sounds like a visit to a Volvo approved installer might be a good idea.

BTW my boat has a 130 saildrive which is 2.19. Similar size boat - bit longer on the waterline and bit lighter. Came as standard with a 16*13 fixed 2 blade, but is now fitted with 16*11 2 blade FlexoFold which is spot on.
 
I am reading the OP rather differently to Tranona. If he's only getting 4-4.5 knots at 2500 rpm and that the engine will over rev seems to indicate to me that he is under rather than over propped. I have a D1-30 in my Westerly Ocean 33, albeit with a saildrive, and with a clean hull I get about 6 knots or slightly over at 2500 revs and something over 7 knots flat out at about 3100.
 
richardbrennan said:
I am reading the OP rather differently to Tranona. If he's only getting 4-4.5 knots at 2500 rpm and that the engine will over rev seems to indicate to me that he is under rather than over propped. I have a D1-30 in my Westerly Ocean 33, albeit with a saildrive, and with a clean hull I get about 6 knots or slightly over at 2500 revs and something over 7 knots flat out at about 3100.
Click to expand...

You are right. I should have read it more carefully rather than concentrating on the query about the reduction ratio.

So the observation that the ratio should be 2.35 in forward is correct. if the reverse ratio of 2.7 had been used to calculate the proip it would give a larger size. However if the calculation was done for 2.35 but then run at 2.7 (ie in reverse but with a LH prop) it would be underpropped.

BTW I have the same engine/drive as you in my Bav 33 and get similar speeds to yours.

So the OP needs to find out which way the box is running and the size of his current prop before deciding what to do.
 
Very rough calc: decide on your optimum hull speed, maybe 1.4x sq root waterline length. Convert to ins/minute. Then calc pitch, a 12in pitch would progress 12in forwards for every revolution, through butter, but will slip about 30%, so 8.4in. So, 3000 revs @ 2.35:1 = 1185 shaft revs/min. Hull speed, say, 7.5 kts =9120 ins/min. 9120 ins @ 1185 revs= 7.7ins/rev. Add on 43% for slip, 11ins. That would be the pitch. Or just ask C&O engineering.
 
Thanks for all the help and info. I will go to the boat at the weekend and calculate the ratio. My current prop is a LH prop and maybe this is a silly question but lets assume it is set up for 2.7 in forward (explaining my lack of power) would that then mean i have 2.35 in reverse so if i upsize my prop for the 2.7 ratio then the engine would labour when i put into reverse? Volvo seem to suggest RH for forwards so that would mean a new shaft as well as prop?
 
Sounds like when the engine was fitted they did not change the prop. LH props were common on older engines. 2.35:1 is the correct ratio for forwards. It is quite common to have a different ratio in reverse and it does not make much difference in practical terms because you only use lower revs/speed in reverse. With some feathering props you can set the pitch differently from forwards. i did this on my old boat because it was underpowered so we had a steeper pitch for reverse to give a bit more "bite" at low revs. However with a well matched power set up such as you have this should not be necessary.

Without wishing to be too alarmist, if whoever installed the engine made the basic mistake of not changing the prop one might question the whole installation.
 
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As you have a Westerly Falcon, the D1-30 was obviously a replacement engine at some stage. Do you know who fitted it as when I had mine fitted the dealer would not sign it off and validate the warranty until we had a sea trial and confirmed that the engine reached its design maximum revs at full throttle.
 
Hi Tranona, you have hit the nail on the head. I knew when I bought the boat last year that there was a problem with how the engine was mounted. I ended up taking engine out and re-mounting – in one instance I had to re-drill and tap the engine bed as the mount was so far out. In re-installing the engine I also discovered numerous other shortcuts that had been taken so it’s no surprise to me really that the prop is wrong! And Yes all this was done by a Volvo dealer!!!! I always thought buying a boat with a new engine would be an advantage but not so sure any more. The prop on the boat is a LH kiwi prop which already goes to max pitch in reverse. I am afraid that if I simply fit larger blades to the prop it will be fine in frd’s with the 2.7 ratio but when I go into reverse, the max pitch on the prop combined with the 2.35 ratio may be too much load for the engine. I am leaning towards reverting the gearbox to operate as designed with 2.35 in forwards and changing prop to RH fixed. Interested in any thoughts opinions on this plan?

Hi, richardbrennan, yes I know who fitted it back in 2013 under the previous owner but as I mention above it was not a good job. Do you have a falcon yourself? Would be interested to hear your cruising revs and speed if so and what prop you have?
 
Fixed 2 blade 17*13 would be fine - but if you buy from somebody like Sillette then give them your boat data and ask their recommendation. The sizes I gave are from the Procalc programme on www.castlemarine.co.uk They also supply props so might be worth a call to them as well. This would be the most economical solution at around £300. Alternatively if you have the money, definitely look at a FlexoFold 2 blade from Darglow Marine. You should get just over 7 knots at full revs and cruise at 5.5 at around 2200 rpm.

BTW think richard has an Ocean 33. As I mentioned earlier I have a new Bav 33 with a D1 30 but on a saildrive with a FlexoFold. I get a bit more speed because of the much longer LWL and a bit lighter. Prop sizes are not comparable because saildrives are 2.19:1 reduction.

Hope this helps.
 
mj81 said:
Hi Tranona, you have hit the nail on the head. I knew when I bought the boat last year that there was a problem with how the engine was mounted. I ended up taking engine out and re-mounting – in one instance I had to re-drill and tap the engine bed as the mount was so far out. In re-installing the engine I also discovered numerous other shortcuts that had been taken so it’s no surprise to me really that the prop is wrong! And Yes all this was done by a Volvo dealer!!!! I always thought buying a boat with a new engine would be an advantage but not so sure any more. The prop on the boat is a LH kiwi prop which already goes to max pitch in reverse. I am afraid that if I simply fit larger blades to the prop it will be fine in frd’s with the 2.7 ratio but when I go into reverse, the max pitch on the prop combined with the 2.35 ratio may be too much load for the engine. I am leaning towards reverting the gearbox to operate as designed with 2.35 in forwards and changing prop to RH fixed. Interested in any thoughts opinions on this plan?

Hi, richardbrennan, yes I know who fitted it back in 2013 under the previous owner but as I mention above it was not a good job. Do you have a falcon yourself? Would be interested to hear your cruising revs and speed if so and what prop you have?
Click to expand...

If its a Kiwi prop, you can adjust the pitch easily. The size is related to the engine bhp, by & large, and it sounds like you just need to increase the pitch.
I would not worry about changing it, if the gearbox can be run in either direction for ahead, just turn the set screws near the blades root.
If you decide to change it, contact Vecta Marine and they will advise if it can be converted to RH and whether you need new blades.
(My Kiwi is a 17" with the pitch equivalent to about 12-13" 46bhp @ 3000rpm Marine Power MP446 engine, 2:1 reduction, 6kts at 2000rpm, ~7.6 kts at 3000rpm (hull speed), 36' 10t long keeler. 17x12 rounded up according to Propcalc)
 
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As Tranona says, I have an Ocean 33 which is about 1000 lbs lighter and probably has a slightly more easily driven hull compared to your Falcon. As I said in post 9, I get about 6 knots or slightly more at 2500 rpm with a reasonably clean hull and prop, and something like 7.2 knots flat out at about 3100 rpm. My prop is a three bladed Volvo folder, I cannot remember the size, but I think the pitch is 11" and I have a saildrive.
 
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