Yanmar 1GM water pump

ianc1200

ianc1200

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Anybody with knowledge of how easy it is to get a water pump off a 1GM? The screws & cover plate on my 1GM are very corroded, but the bolts attaching the pump to the block are in good condition. If I release the pipes, undo the bolts, does the pump off relatively easily?
 
Yes. Once you have removed the screws through the timing cover into the block it just pulls out. Be careful with the heads of the screws as they are made out of a special brand of Yanmar cheese. The end of the shaft has a peg that fits in a gear wheel for drive. If it is leaking, check that it has not corroded the oil pipe underneath.
 
From my experience with 1GM's, the pump comes off easily, as in Tranona's post, but you have to make really sure that the pump isn't leaking from the shaft seal at the rear of the pump. It this seals leaks, salt water drips onto the oil pipe below it, which is made of steel and is hot when the engine is running. This is an ideal environment for rust and the oil pipe doesn't last long. A leak in the oil pipe could cause a major problem with the engine.

The Yanmar spares are very expensive, so I bought banjo fitting and brazed them onto a length of copper pipe, bent to the correct shape by hand. The copper tube worked OK, it was much cheaper, and lasted longer than the Yanmar steel part.
 
If you can, use a hexagonal socket on the bolts (10mm). There's one of the little swine that needs a ring spanner unless you take the pulley off the crankshaft. Murphey states this is the one you'll cheese as it's the least accessible. The torque should only be ~ 10Nm but corrosion can be a swine when you need to break friction and get the bolt turning. If you do damage this bolt head, the pulley will have to come off. When replacing the pump, a little lanolin or teflon grease on the threads will help in future. You'll find SS replacements have slightly larger heads (11mm) or at least the ones I used did.
 
Like above , I replaced the fixings on mine before the cheese ones became difficult to remove.

From memory M6 x 18 long setscrews , hex head.
 
One last tip, if you do damage one of the bolt heads, a set of IRWIN Bolt Grips will save you much anguish trying to remove said bolt. They are available from e-Bay quite reasonably and the basic five will do most of the Yanmar heads. There is an extended set for some intermediate AF sizes but I've yet to use any of the ones I have. They'll probably come into their own when I get round to the old cub in the bottom shed.
 
That looks pristine compared with most. Don't see any sign of current leaks from the seal, so no need to remove the pump. Take the face plate off, clean it up, change the impeller and reassemble with a new gasket. Better still replace it with a Speedseal to reduce the chances of weeping at that point and make impeller replacement easier. You will appreciate that once of you have removed the standard plate, particularly extracting the screw behind the pulley.
 
It looks as if some charming fellow has replaced the 7mm hex head bolts with phillips head bolts. If so this may prove something you can't address with the pump in situ. I endorse the speedseal route but council buying a spare knurled knob screw as one of mine distorted and another was lost deep in the bilge. They aren't magnetic so you can't pick them up with a magnet (at least that's my experience.

With the pump off, you can dress the face on 800 grit wet 'n dry pasted on a sheet of glass before reassembly.
 
This is the problem, can't get the phillips head screws to turn, so getting the pump off perhaps a better option if the third unseen bolt holding the pump on is in similar good condition. I had this engine put in about 1989, almost 100% fresh water use, as a wing engine, and very rarely used in anger. I suspect the impeller has never been changed.
 
I did post about the Irwin Bolt-Grips. The smallest one might work, although I think I used it on the Yanmar 7mm hex head bolts. You'll certainly nee sit n the bench to get the phillips out anyway. Good luck!

BTW, the impeller was probably changed when the phillips screws were put in. Not that it helps.
 
The bolts holding the pump are flange head - which tend to slip more than normal hex head and washers. Just make sure you have a good fit ring on the inner bolt - and be careful ! Being slopped with yanmar grey paint does not help either.
Change them for SS hex head - once out and free and well greased - new bolts will give you no problems in the future.

You soon find out if the seals are leaking - water belts out from the bottom of the pump.

Seals are cheap - easy to replace ( 1 circlip to remove bearing and shaft assembly )
There is no gasket needed for the pump - it has a large diam O ring in a groove.
I always remove the pump to do the impellor ( a bonus of nice new SS bolts ) - so can then check the spigots for furring ( they are not that big when clean ! )
 
Again many thanks for the thoughts. I'm lucky in that there's no great urgency to use the engine, and if I make a muck up well it can come out of the boat relatively easily. But will get the Irwin Bolt-Grips, and change to better bolts if lucky.
 
Ian_Edwards said:
The Yanmar spares are very expensive, so I bought banjo fitting and brazed them onto a length of copper pipe, bent to the correct shape by hand. The copper tube worked OK, it was much cheaper, and lasted longer than the Yanmar steel part.
Click to expand...

My local Pirtek branch made me up a pair of rubber hoses. Took about 20 minutes, cost about £35 including four new bolts as the banjos were a little thicker than the Yanmar ones.
 
ghostlymoron said:
There is no gasket needed for the pump - it has a large diam O ring in a groove."
If this is the case, why is there obvious signs of leakage?
Click to expand...

Even an O-ring will leak if it is not well greased with silicone grease (having spent the last few days replacing and greasing 24 of the 40-ish O-rings on a Range Rover air suspension system! :ambivalence:)

Richard
 
We have just had this same issues, but with a bit of northen engineering it works.

the nut is a 10mm so if you get a 9mm socket and extension and hammer this onto the corroded head (use alot of force) it dislodges the rust and frees the bolt then with alot of force into the thread (not torque) it shoudl pop off,
the others came off using some nedle nosed molegrips.

after a few hours swearing ours came loose this way
 
ianc1200 said:
Again many thanks for the thoughts. I'm lucky in that there's no great urgency to use the engine, and if I make a muck up well it can come out of the boat relatively easily. But will get the Irwin Bolt-Grips, and change to better bolts if lucky.
Click to expand...

I've just tried my smallest Bolt-Grip on a cross headed machine screw and it was too big. Motor Cycle News had some tips regarding removing these last week, so I have to hunt the recycling bin and dig out the article. I"m also going to look at the extension kit for the Bolt Grips to see if there's a smaller one there.

Just looked, the smallest on in the basic set is 3/8" (~ 9mm), the expansion set has a 5/16th" (8mm). Check out Cromwell Tools for best price found today.

The article is in this week's MCN, the article in the paper is too big to scan and post here. You might find it on their website, but it's pretty good. Apart from the usual "apply penetrating oil, heat and/or shock by tapping the head, it advises hammering an oversize replaceable bit into the old head, using an impact driver, a mole grip on the screw head, cutting a new slot and applying direct heat to the bolt using one of those portable gas torches sold for soldering when you don't have electricity (like on the boat).
 
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One last hurrah on this. I had a pair very corroded, phillips headed bolts to remove today. Using a scraper and a wire brush, I removed all the corrosion around the bolts I could. Then soaked the threads with GT85. I hammered an oversize bit into one and managed to remove it but the second did not succumb to this treatment. Nor did direct heat enable me to shift it. A further soaking in GT85 followed by gripping the head with a small mole wrench and moving back and forward eventually broke the friction and enabled me to remove it. +1 for the MCN article.
 
One last update for anyone still following this thread, the 8mm Irwin Bolt-grip can be persuaded over the phillips head on 4mm screws.
 
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