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Message board > Engines > Yanmar Poor Quality Bolts

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Message 1 of 8
Posted by member Peter Cox on Monday 8 June 2015

On my twin 6LPA-DTP engines, several of the bolts securing the impeller cover plates have simply corroded away or the heads have fallen off, so that the remaining studs will have to be drilled out. Not a cheap job, as the entire pumps will have to be removed. My marina workshop says that this is the second of these jobs they have had to do on this type of engine in the last few weeks. Why does Yanmar do this? If you remove the cover plate on any Yanmar, it might be worth renewing the bolts as routine.

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Message 2 of 8
Posted by member John on Tuesday 9 June 2015

The same problem Peter. I guess a bit of salt water gets in and causes corrosion as the engine gets older. Some had a bit of thread left so was able to remove these with WD40 and patience, although not easy to get at! One had to be drilled out and retapped, done in situ but would not be possible with some of them.

They seem to be M4 brass (Yanmar Product Code WPS-M4) and cost £1 or so each. These are actually Johnston pumps.

I was thinking of replacing these with phosphor bronze studs and then using nuts to fix the cover, and possibly a little waterproof grease on the threads to minimise corrosion.

Best of luck

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Message 3 of 8
Posted by member Peter Cox on Thursday 18 June 2015

The boatyard has now replaced the brass screws (sorry - not bolts, as I originally wrote) with stainless steel ones. Both pumps had to be removed from the engines; fortunately this gave access to the 'back' of the screw holes so that the remaining stubs of the screws could be unscrewed, after a little modification, from there, without drilling and tapping. I took the opportunity to have the impellers replaced. The cover plates were a bit worn, so were reversed. The boatyard said that the other boat, not a Hardy but the same engines, had one of the cover plates held on by only one remaining screw; disaster narrowly averted!

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Message 4 of 8
Posted by member Peter Cox on Tuesday 27 June 2017

Bad news concerning a Hardy 36 next berth but one to me (not an HOC member) and I think with the same Yanmars as me; apparently the impeller cover plate fastening screws failed and the boat nearly sank. Second-hand news in the marina is that the bill will be in excess of £70k. Check/replace yours!

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Message 5 of 8
Posted by member DARKIVY on Wednesday 28 June 2017

Thanks Peter

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Message 6 of 8
Posted by member Simon Kidd on Monday 24 July 2017

Quite Shocking to hear about this, brass is just not suitable for use in salt water. I've found a few issues on smaller Yanmar engines, though it's very rare to find similar issues on Volvos (Can happen though).

My old Caterpillars had Johnson Pumps and no issues there (though heat exchangers were a different matter!!, nor the Sherwood pumps on the Onan genny.

I've found a number of vessels with corroded A/P bracket stern gland and rudder gland bolts recently (Dezincified thus now made of copper!) - make sure they are all checked whenever ashore - use a good hammer and look at the bolt heads for the pink colour as a tell tell for dezincification..

I'll be keeping a sharp lookout on the pump covers, and sticking with Outboards for now!..

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Message 7 of 8
Posted by member Peter Cox on Friday 1 September 2017

Another twist to the saga: according to my marina workshop manager, replacing the original brass screws with S/S ones is an improvement but even the S/S screws do not last for ever, just longer than the brass. The 36 that nearly sank in my marina already had the S/S screws but they too failed. The manager said that the real problem is that the cover plates only have four screws, ideally there should be six or eight, so that if several fail, the cover plate will stay on, at least for some time.

Marie tells me that Hardy have taken the matter up with Yanmar, but I'm not holding my breath for a reply from Yanmar.

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Message 8 of 8
Posted by member Hardy Editor on Friday 1 September 2017

Hi Peter,

I did indeed mention to Oliver James about this problem when I last contacted Hardy Marine, and forwarded him the details which you kindly supplied to me. Oliver was pretty shocked. Iíve not heard anything further as yet, but I do think as a Club we should approach Yanmar directly and see what they have to say.

Iím afraid Iíve not had the time to do this myself, although it was my intention to do so. Iíve only just completed the September issue of the Hardy Owner magazine and sent the file off to the printers for proofing.

However this does sound like a very serious problem, Peter, and we really should take it upon ourselves to investigate further.

Perhaps a contingent of Hardy Owners should make a call (not in the euphemistic sense!) at the Yanmar exhibition area at the Southampton Boat Show Ė September 15thĖ24th (Stand E050 Ė email: customerservices@barrus.co.uk) and politely point out the facts as we understand them and ask them to comment on our findings. Iím game if anyone would like to join me. Iím unable to go on either the Preview Day (Friday 15th) or the closing day (Sunday 24th) but will let you know when I can visit, so perhaps we can meet up.

Anyone interested? Just contact me and let me know.

Marie OíConnell HOC Editor

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