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seized Gearbox md3b from a Pentland

Posted: Wed May 02, 2018 9:36 pm
by jonty51
Long story short, we have a Pentland, with a ageing MD3B in it. Engines no problems starts on the key with plenty of power. however on coming along side she got stuck going from astern to neutral, with a horrid grinding noise. The engineer recons the shaft has seized as there was no oil in the gear box.

Question is, does anyone know anywhere I could obtain a replacement box reasonably?

Kind Regards
Jonty :D

Re: seized Gearbox md3b from a Pentland

Posted: Thu May 03, 2018 2:48 pm
by BrightStar
Be worth trying putting oil in, drop it into neutral and turn it over with the valve lifters down, on the winding handle, then after a couple of fast revs (by hand) pop it into ahead and give a few more revs and then astern for a few revs.

If the prop turns in each direction without any outward signs of trouble, start the engine in neutral, run ahead for a while and then try astern and see what happens. If you are alongside, you can hard against your springs for a reasonable time to convince yourself that all is OK (or not :( )

If it looks encouraging, suck the oil out of the gear box and strain it through some kitchen roll paper and look for metal flakes. Small quantities not a problem probably, teeth a bit more of a problem)

Refil with clean oil and try again

Hopefully it will be OK!!

You do see these units come up on ebay now and then

Where are you?

Re: seized Gearbox md3b from a Pentland

Posted: Fri May 04, 2018 10:45 am
by TyroSailor
I had a similar problem with my old MD2b - the engineer who was supposed to service the engine in my absence (I won't do that again!) didn't check the gearbox oil and.....

I did exactly as suggested above (bar the cranking it round by hand, which seems a good idea) and filtered out lots of very small bits of metal; on the rare occasions I could get the engine to run subsequently (long story) the gearbox seemed to work.

Now, I have a shiny new yellow engine!

Re: seized Gearbox md3b from a Pentland

Posted: Thu May 10, 2018 8:30 am
by jonty51
HI we are down in Fareham,

Tried filling it up, its a bit of a some time does, sometimes doesn't then it gets stuck again :( engineer thinks its a rebuild or recon one :(

Thank you for your advice greatly appreciated

Re: seized Gearbox md3b from a Pentland

Posted: Thu May 10, 2018 5:10 pm
by BrightStar
Might be worth, first that the cable is free to move through its full travel, then disconnect it and ser if thr gear selector is free to go from ahead to astern, if it is then problem is in cable or cockpit gear change mechanism, if it isn’t free to change gear by hand, then worth taking the top plate off and have a look see inside.

These are robust units

Re: seized Gearbox md3b from a Pentland

Posted: Thu May 10, 2018 6:08 pm
by UserError
Mine seized completely, suddenly.
What sort of stuck?

Mine was working fine then seized. Oil was low but just on the dipstick. Not sure how the actuator is lubricated - presumably by oil fling from the rotating parts. Or not if there is insufficient oil...

If you're able to undo the actuator bolts in situ, might be worth a look. They are 10mm. Or were. Mine were a bit rusty & I used a mole grip on two of them. Toolstation do a pack of 10 M6 20mm bright plated high tensile bolts for pennies.

I didn't know this and took the gearbox out. First thing I took off was the actuator arm assembly. Turns out this was seized solid. I dismantled it, cleaned off the brass eccentric pillar-thing with wire wool & the housing innards. Drop of oil on the shaft & reassembled. I can change gear by hand on the actuator, which I take to be a good sign.

It's going back in the boat tomorrow, so we'll see.

Re: seized Gearbox md3b from a Pentland

Posted: Sat May 12, 2018 10:23 pm
by UserError
Just a heads up. Mine still isn't back in as I noticed something on the engine floor, below the drive coupling: it was a piece of the rubber spider.
If you take your gearbox out, take the spider out to check it over.
It comes out easily by hand.
IMG_20180512_135650177.jpg
Broken rubber spider.
IMG_20180512_135650177.jpg (64.6 KiB) Viewed 670 times