Volvo Saildrive - Propeller Replacement or Renewal

[upthesolent]

I have a standard (not the SL) Leisure 23.

The 3 blade prop on my sail drive looks like a mouse has been eating at the ends of the blade, and pitting is now quite abundant on them as well.

Replace or Refurbish?

My main problem is I am not sure what saildrive it is on my February 1979 boat. I am guessing the Volvo 120 or 110? The engine turning the prop is a Vetus M2.C5 which is an 11 hp twin (torque 26Nm) and done less than 200 hours since new.

I havn't a clue where to start though assume once I have sourced a prop they are straight forward to fit. I would be looking at doing it over a tide (or 2) on the scrubbing berths.

Just as an afterthought, could the deteriation of the prop be a possible cause of the engine running a little hot (slight steam) when under power? (Cooling water comes out cold when at tickover)

Thinking out aloud I think I may prefer for a new prop as the problem would be fixed immediately whereas refurbishment would take some time and require a tow from scrubbing grid to mooring and another one back.

Thanks in advance.

 

[Mrnotming]

Hi Upthesolent! Sorry to hear your prop is Upthecreek!
The prop is held on by the large cone shaped alloy nut, and most importantly retained by a centre hexagon keyed bolt and lockwasher. There is also a plastic washer shim between the back of the prop on some models and also a spinning disc on the shaft which cuts fishing line etc.Two reasons at least for the disappearance of bits of prop. one would be cavitation and this might occur if the pitch was not coarse enough to make the prop "grip" properly.You engine would in this case tend to rev easily to its designed limit or beyond.Another reason could be an anode made from less that perfect zinc or perhaps an inland waterways one of magnesium alloy fitted by mistake. More commonly, other boats AC shorepower electrical systems, or your own AC system, cause minute currents to flow and the prop seems first to go on the saildrives, despite having an anode. Being moored up to a metal pontoon or metal piling also can exacerbate the problem. A third reason could be antifoul containing copper was used on the leg or prop.This is a nono, special stuff required Trilux I think is one brand. Search the forum under "gavanic blocking diode" or similar phrase to find out about fitting a unit in the incoming earth wire to help prevent the problem, but only if you have shorepower!

As regards doing the job on a tide, if you can pick the antifouling out of the hex bolt and have a good sharp hex key at the ready, you may get lucky, as it only needs a strong bar of about 8mm diam to undo the large cone.The prop is on parallel splines and should pull away readily. It should be greased with the Volvo grease when reassembling so it continues to come off easily! A new bolt and lockwasher is indicated by Volvo as required, but perhaps some thread locking compound would give sufficient peace of mind if you cannot source these items.

I never thought whether the material of your prop was bronze and not alloy, but now that I have I believe the anode should be replaced more often because of the mix of metals being further apart on the galvanic scale.
The alloy props from Volvo are reasonably priced and can last maybe four or five years if lots of care is taken in their repainting regime.
Anything else bothering you, I'll try to help.

 

[PeterGibbs]

Sounds like a new prop is in order. Get on to Keypart at Kings Langley - they'll source one at a good price. Hardly any saving in having the old blades built up and rebalanced.

Probably a 110 leg - should be a straight forward fit for the new prop, but if the old one hasn't been off in years it might need some elbow grease - no heat!

Prop most unlikely to account for steam in exhaust. But possibly connected to your other situation - exhaust water coming out cold when idling and even after running up. Check the impeller is intact - no lost blades - & working properly (not running loose from its core) to give you proper water throughput. Then check the thermostat - may need replacing ( Keypart again) Final thought - heat exchanger is getting furred up and water not getting through when idling: seek advice, depending on the setup - cleanout possible but replacement not cheap.

Good hunting!

PWG

 

[jackho]

Not a technical expert in this field but suspicious there may be a wider issue with your sacrificial anodes and internal corrosion in your sail drive if your prop is acting as the anode and having problems with the saildrive.

 

[upthesolent]

Thank you all for your replies. I had covered the saildrive leg in a product made exactly for that purpose. The boat does sit in mud all year round, but last year when I noticed the problem, I thought it strange that the anode collar behind the prop was in very good condition. The main hull anode though, clearly showed signs that is was being used for its sacrificial purpose and was replaced.

I shall have to check the collar anode when I get the boat out of the water in the next few weeks. If it is still good, then I shall be back to scratching my head as to what to do!!

 

[TeamSpirit]

If the edges of the blades are 'frayed' they can be refurbished but not worth the expense if you have pitting in the metal of each blade - dump it and replace. Have had the same issue this year? and am collecting my new prop next week circa £240 squid.

 

[gavin_lacey]

If the leg anode is in good condition it is probably not making a good electrical contact with the leg. Voltages are low so contacts need to be very good. Make sure the contact points are clean/lightly abraded.