I have just been left a Beneteau Oceanis Clipper 381 yrs 1996 this boat has not moved in five years I have got the engine running it goes into gear and the shaft spins but no Thrust . On a lift out I have found the prop is missing. The boat has a Volvo MD22L Diesel of 50 HP .RPM 3000 Gear ration 2.47_1 can anyone please help with a standard three blade prop size .
Propellor missing help
- Thread starter john duncan summers
- Start date
Contact any prop maker or prop shop for a quote. You will need to have the following information ready for them:
Engine make and model (HP may be sufficient)
Transmission final gear ratio (it should be on a permanent plate affixed to the transmission)
right-hand (clockwise) or left-hand (counterclockwise) shaft spin in forward
prop shaft diameter in mm and whether standard taper or some other
keyway measurement (depth and width) measured with a caliper.
you’ll need to order a shaft key also. If not a standard size a machine shop can make one for you In bronze or stainless.
Edit: I recommend you find a local specialty prop shop who can make sure you get everything right. A local boatyard can refer you to whoever they use. They will require you to bring them your existing shaft and coupling so they can measure it and make sure everything fits properly. They will “face” the coupling, verify the shaft is true, and lap the new prop to the shaft so that it is a proper fit with precision tolerances. You might not like the price but it will save you a lot of headaches and assure a vibration-free and problem free installation. It’s a non-trivial thing in time and money to haul your boat to fix vibrations or other prop/shaft issues.
Also, make sure your shaft is properly aligned when you put it back in. It‘s not difficult but it takes patience and technique. You can find youtube instructions or you van hire a mechanic to do it for you.
Engine make and model (HP may be sufficient)
Transmission final gear ratio (it should be on a permanent plate affixed to the transmission)
right-hand (clockwise) or left-hand (counterclockwise) shaft spin in forward
prop shaft diameter in mm and whether standard taper or some other
keyway measurement (depth and width) measured with a caliper.
you’ll need to order a shaft key also. If not a standard size a machine shop can make one for you In bronze or stainless.
Edit: I recommend you find a local specialty prop shop who can make sure you get everything right. A local boatyard can refer you to whoever they use. They will require you to bring them your existing shaft and coupling so they can measure it and make sure everything fits properly. They will “face” the coupling, verify the shaft is true, and lap the new prop to the shaft so that it is a proper fit with precision tolerances. You might not like the price but it will save you a lot of headaches and assure a vibration-free and problem free installation. It’s a non-trivial thing in time and money to haul your boat to fix vibrations or other prop/shaft issues.
Also, make sure your shaft is properly aligned when you put it back in. It‘s not difficult but it takes patience and technique. You can find youtube instructions or you van hire a mechanic to do it for you.
Last edited:
Just as important, find out why the prop is missing. Props just don't fall off for no reason. It might not have been installed correctly or there might be a serious galvanic corrosion issue that caused the prop to erode and fall off.
Hi Larry
I have already made a new shaft with a basic tapper which I can adjust when I find a replacement prop .
I have already made a new shaft with a basic tapper which I can adjust when I find a replacement prop .
Untouched on its mooring for five years and three Anodes have done their job but most likely stopped about two years ago .
As dlochner said ''Props don't fall off for no reason''. You said 3 anodes did their jobs but not for the last 2 years. Be that as it may, on a mooring you're unlikely to get electrolysis or even galvanic corrosion to wipe out an entire prop in that short of a time. If that was the case the strut would be severely damaged as well. Are prop nut and pin missing also ? If so then poor installation may be the cause of the missing prop. Depending on engine, if no pin or locknut, just putting her in reverse could unscrew the nut and you lose the prop. May be worth having a diver check the bottom around the mooring. Or it could have been stolen 
. As for finding another prop, with all the info as per Captain Larry, as good prop shop will be your best bet. Good luck
. As for finding another prop, with all the info as per Captain Larry, as good prop shop will be your best bet. Good luckI have only had the boat for five months 381 Do not have a P Bracket the shaft comes straight out of the centre of the hull. The shaft is total scrap that is why I have made a new one already .All I need is any prop info from an owner of this Model of Beneteau .
An easy mistake an uninformed installer might make is using an Imperial measurement for the prop while the shaft is metric. While close, a 25mm shaft is not the same as a 1" shaft.As dlochner said ''Props don't fall off for no reason''. You said 3 anodes did their jobs but not for the last 2 years. Be that as it may, on a mooring you're unlikely to get electrolysis or even galvanic corrosion to wipe out an entire prop in that short of a time. If that was the case the strut would be severely damaged as well. Are prop nut and pin missing also ? If so then poor installation may be the cause of the missing prop. Depending on engine, if no pin or locknut, just putting her in reverse could unscrew the nut and you lose the prop. May be worth having a diver check the bottom around the mooring. Or it could have been stolen
If the shaft was scrap what makes you confident the coupling is true?
If you're a machinist you understand why I'm emphasizing these things. If not, you may need more than you think if you haven't had the new shaft fitted and lapped to taper and shaft fitted to the coupling in a machine shop, and the coupling faced to be sure it's true.
Are you sure your new shaft doesn't have more than the allowed run-out? Typically the maximum runout for a low speed shaft (under 3600rpm) is 0.002 inches (2 mils). If you just put these components together assuming they're new and good you may find yourself chasing expensive problems. This is the voice of experience after multiple haulouts just to try to remedy a nasty vibration
.
Last edited:
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,741
Larry provides great detail for your prop shop. Additionally they will need to know the distance from the hull to the shaft where you expect the prop will be. It will be useful to identify the diameter of the prop.
My post is solely to do with the prop size nothing else so the only person who can answer is an owner of this Model of Boat . I have a Laser alignment
unit . I was a HM Coastguard officer for over twenty years working on our Boats and my Full time employment has been as a Pharmaceutical Engineer
for well over Thirty four years so I am well able to deal with Galvanic issues . Regarding prop calculators I have not found one yet that works correctly .
unit . I was a HM Coastguard officer for over twenty years working on our Boats and my Full time employment has been as a Pharmaceutical Engineer
for well over Thirty four years so I am well able to deal with Galvanic issues . Regarding prop calculators I have not found one yet that works correctly .
I'm not sure why you think this is true. There is nothing magic about that boat. As a moderate-displacement cruiser, your boat benefits from good thrust at low RPMs but drag under sail isn't as critical as with a performance-oriented design. It will take a 16" prop and given the specs you provided, the math works out to 11" or 12" pitch.
Your shaft RPM at WOT is about 1215 and at 80% (cruising throttle), that's about 970 RPM. At 2400 RPM engine speed (about 970 RPM shaft) and 35% slip, a 16x11 or 16x12 prop gets you:
- about 6.5 - 7.2 knots (the sweet spot for cruising)
- reasonable efficiency
- full use of engine power curve without overloading or under-revving
That's not true. The diameter should be as large as it can while retaining a 20% gap with the hull. You should be able to measure that easily, and it will be the same for all owners of your model boat. The pitch will be determined by the specific model prop you get, and not by what is on another owner's boat (unless you get the same specific model prop). For example, props for our boat are 18x12 for a fixed Michigan Wheel, 18x16 for folding Volvo, and 18x13 for folding FlexOFolds. They all perform the same, but have different pitches. The prop manufacturers will determine the pitch.
Mark
Suggest that you contact Ward Richardson at Beneteau USA for info on standard prop supplied on the 381. (Ward.Richardson@Beneteau.com). Just for comparative info, my 343 had 3 blade 17 x 11 RH prop with 25 mm bore. Beneteau #064122. 12,000 lb gross weight, 30 hp Yanmar.
Last edited:
The Beneteau spare parts site lists all of the following possibilities for the 381 -
I presume those vary based on model year and engine, and maybe other factors. Ward might know which one goes with which, but I think a prop manufacturer would be a good bet to size their specific design relative to your specs.
I presume those vary based on model year and engine, and maybe other factors. Ward might know which one goes with which, but I think a prop manufacturer would be a good bet to size their specific design relative to your specs.
Well, if you are certain of the shaft diameter (25mm or 30mm) and know if your old prop was right hand or left, that narrows the options to one or two. As @Davidasailor26 mentioned, looks like it was dependent on date of manufacture and engine /transmission combination.
On my '05 model, Ward was able to look up the "build sheet" & send me a file, including the prop that was used as well as options such as engine, keel option, upholstery option, etc.