Help - undoing stuck screw (tight access)

[superheat6k]

I today attempted to renew the seawater impellor on my stbd engine. Volvo Penta decided it would be sensible to mount the pump in direct line with the oil cooler, and left insufficient space to even get a stubby screw driver in.

Due to the position of the engine there is only approx 150 mm of access space this side of the engine, and the upper screw cannot even be seen.

I got 4 of the 6 screws free, but the partially obstructed two at the top would not budge, as I could not apply enough direct force into the screw driver and turn it at the same time with only one hand.

Any tips on this one would be appreciated.

Also the thread is similar to M5, but marginally smaller - does anyone know the specific thread as I will replace the slotted screws with hex head bolts, so at least I can get to them in the future.

Thanks

 

[noelex]

Get a small ratchet drive kit that comes with screwdriver bits. With the leverage you should have less problems.

 

[volvopaul]

I today attempted to renew the seawater impellor on my stbd engine. Volvo Penta decided it would be sensible to mount the pump in direct line with the oil cooler, and left insufficient space to even get a stubby screw driver in.

Due to the position of the engine there is only approx 150 mm of access space this side of the engine, and the upper screw cannot even be seen.

I got 4 of the 6 screws free, but the partially obstructed two at the top would not budge, as I could not apply enough direct force into the screw driver and turn it at the same time with only one hand.

Any tips on this one would be appreciated.

Also the thread is similar to M5, but marginally smaller - does anyone know the specific thread as I will replace the slotted screws with hex head bolts, so at least I can get to them in the future.

Thanks

On the 60 series engine I use my snap on pliers that have serrated jaws to grip the screw at 90 degrees to the thread, works a treat every time. Throw the old screws away and buy new with 8 mm heads on.

 

[landlockedpirate]

I have some of these, only use them once in a blue moon, but fantastic when you need them.

Offset Screwdriver

 

[Poignard]

http://www.amazon.com/dp/B00004T7TY...e=395261&creativeASIN=B00004T7TY&linkCode=asn

Good idea to replace the slotted screws with hex headed ones (or wingscrews, if you can find them)

 

[David of Essex]

Off set screwdriver with a wedge behind to keep the screw driver forced home.
David

 

[superheat6k]

Pump screws

Thanks - I will now try the tips provided.

VP you mention replacing with 8mm hex. I did replace one yesterday with an M5, but this was very tight to get in, and the other three I managed to get out I could not start the M5 bolt.

I also used an overlength bolt with a couple of extra nuts on, so next time I have got something to grab hold of.

Could you confirm you use an M5 ? Perhaps I just need to run an M5 tap down the holes !

 

[kashurst]

I replaced mine with M5 x 8mm cap head bolts. These have a knurled cap so you can turn them with your fingers when putting them back in, and the cap takes an allan key so you can be sure you have good control in a limited space and without being able to see what you are doing. (my starboard pump is a pig to see - I use a mirror on a stick)

Be careful when you re-tighten the bolts as the pump body is brass and its easy to overdo it. I aim for just to the point where they go stiff + 1/4 a turn. If it leaks just tighten a tad more.

Another useful trick is to make 2 lengths of M5 thread to act as threaded studs.
(cut the heads of some M5 x 30mm bolts), screw these by hand into two of the pump body holes on opposite sides so they stick out a long way. Now you can put the greased gasket and cap on over the studs and let go! The grease keeps everything together and the studs keep everything aligned. Both hands are now free to put the bolts in loosely and jiggle the cap/gasket about without it all dropping into the bilge. When you have four bolts in, take out the thread studs and replace with bolts and then tighten them all up carefully.

 

[kashurst]

regarding the threads - the original thread is a UNC thread (I think) the M5 thread has the same pitch but the tip to root dimensions are slightly longer so it will be a bit tight at first. Metric threads have a triangular thread form, the UNC is rounded off tip and root. If you are having trouble best to check and take the original pump bolt down to halfords/swindlery and test it with an M5 nut. Pretty sure it will go on smoothly.

 

[rosssavage]

Close - its 5/32 UNF if it' a TAMD 60. I replaced some two days ago on a princess 414 with hex heads - a million times easier!

When you get the cover off, the impeller will be a mare to get out for the same access reason. Squirt a load of spray grease in there and turn the engine over (on the crank pulley nut, with the STOP solenoid ON!) it should slide out easily then.

 

[superheat6k]

Thanks & I done it !!!

I think Rossavage must have been looking over my shoulder today !!!

It is a UNC, and Aladdins Cave had some original Johnson Phossy Bronze screws with raised heads, which are now proudly mounted.

The M5 is a tad larger diameter, and trying to get a tap in where this is situated, well !!!. With the brass case I was concerned forcing an M5 in could split the thread housings which run down the outside of the pump casting, and getting this pump off the engine to replace fully would be a couple of days work.

I thought about filing some flats on, but the new screws have distinct raised parallel head so next time there is something for the moles to get hold of. They are also thoroughly greased.

Thanks to Volvopaul in particular as it was his tip with the moles that I managed to get one of the stuck screws to free (Ouch - I pinched my fingers a few times first). The final screw, which was at the top and obscured below the pump outlet pipe, was a complete b##t##d, so instead I simply rotated the whole cover plate and that rotated it free (good job as once I had done that there was no going back).

I also bought the somewhat overpriced Jabsco puller, for which I had to use a separate M12 x 75 setscrew as the puller bolt supplied with tee handle was far too large. Without this there was no way the old impeller was coming old.

Before I could get it out I thoroughly soaked it in spray PTFE lubricant, spun it up briefly (without the puller mounted) and used plenty of silicone grease to get it back in, plus the aid of a convenient jubilee clip to squeeze the lobes in a bit.

Best of all when I test ran the engine - no leaks.

Peace of mind does not come cheap, but at least I have two, albeit used, extra spare impellers, and the noggin on how to do this awful job next time around.