Bmc 1.5 Smokey

[Minigem]

Is it an oil operated gearbox such as a PRM?

[smitch6]

yes its a prm

[D46]

1 minute ago, smitch6 said:

yes its a prm

Which one there are mechanical and hydraulic in the prm range .

[Minigem]

Sound like a clutch in the gearbox is worn. When a PRM is in gear the engine is locked to the gearbox and the prop speed goes up and down with engine speed. There should be no revving to get the prop to turn. Is the gearbox topped up with the correct oil? 

[smitch6]

yes i drained and refilled the oil,

as i said i have taken off the cables, so maybe they aren't in the correct place.

i think it's a prm 150 

[Minigem]

1 minute ago, smitch6 said:

yes i drained and refilled the oil,

as i said i have taken off the cables, so maybe they aren't in the correct place.

i think it's a prm 150 

That may be a possibility. You could try disconnecting the cable and operating the control lever on the side of the box manually to the full extent of the travel. If you still have to rev the engine to get the prop to turn then I would suggest that the forward drive clutch is worn or there may be a problem with oil mechanism.

[D46]

9 minutes ago, smitch6 said:

yes i drained and refilled the oil,

as i said i have taken off the cables, so maybe they aren't in the correct place.

i think it's a prm 150 

Pretty certain that's a mechanical box and it's quite possible it's a cable issue TBH , if it worked before and nothing has changed but paint it really has to be .

Oil level is by screwing the dip stick back in according to the prm manual .

[Minigem]

10 minutes ago, D46 said:

Pretty certain that's a mechanical box and it's quite possible it's a cable issue TBH , if it worked before and nothing has changed but paint it really has to be .

Oil level is by screwing the dip stick back in according to the prm manual .

Just looked up the PRM 150 and it is an oil operated gearbox. 

[Minigem]

Anyway Smitch. I am going off line now. Best of luck with the problems.

[Smoggy]

If it's in gear the prop should turn all the time at all revs unless a hydraulic setup, I'm no marine gearbox expert so Vaughn may correct me.

I'd guess at around 800rpm idle (another guess).

Edit: Doh missed a page of replies....

[smitch6]

no it didn't turn at tickover which was about 500 i'm pretty sure i had to move lever forward and revs went up to about 10 maybe higher before it appeared to click into gear,

i reckon it needs adjusting as i said i've had it all off

so i'll have a look next week, now i know if that there's not much movement needed on the lever before it goes into gear, 

[Smoggy]

Sounds like the lever need adjusting and it's not actually in gear when the lever reaches it's detent position.

[Vaughan]

This sounds to me like a gear cable adjustment problem. Let's hope it's only that.

The BMC and Perkins tick over at 700 revs and they should be kept nice and slow as the PRM gearbox goes into gear with a bit of a thump, so if the revs are too high this will eventually break the flywheel thrust plate.

Someone has already suggested taking the cable off the gearbox and moving its lever by hand. If it now goes into gear normally, there is your problem!

If it still slips and you have already checked the oil level, then you are looking at changing the clutch plates. Not a difficult job in a PRM, but time consuming. In other words, costly in labour hours!

[Vaughan]

Looking at your video again, I'm not sure that the fuel feed to the lift pump, in coiled copper pipe, would pass the BSS nowadays. I think it would need to be in flexible armoured cable.

The BMC air cleaner that I have always seen is a flat affair with gauze around the sides, and which comes with a side pipe fitting to accept the crankcase breather hose. Maybe worth sourcing a part second hand, perhaps from one of the boatyards, especially Woods, who used to be the BMC agents.

[Vaughan]

Something else, although this is only from memory. That breather pipe is part of one of the push-rod inspection covers on the side of the block. I think this may have been put on the wrong way round as the pipe is normally closer to the air intake, for obvious reasons. This means that the breather hose will be just a short elbow.

[annv]

Hi There should be two breather pipes one comes from the rocker cover and is piped to the air cleaner/silencer this often gets blocked remove rocker cover and clean the other pipe comes from the side plate of the engine loops up then drops down to just above the sump this is the balance pipe to stop the crankcase pressurizing with blow past the rings causing pressure in the crankcase and forcing oil past the rear main bearing cap, if cover and pipes are clear you could have a sticking ring/rings at 1500 revs does the smoke puff out of the breather like a steam engine or is it constant? you could also give it a run for an hour at 2000 revs if still smoking try doesing the engine bores with Red Ex leave for a week then give it a run. John

[annv]

Just seen your other add why not dose your bores with Redex while you wait for a crane it wont do any harm except to your pockit and as engine has been standing for several years without any prep it would be very beneficial as this should have been done when first lifted out John