engine rotation

[doc g]

I am rebuilding a raw water pump at home . Can anyone tell me which way a 12v71TI (stb) engine rotates? Also if I lube the bore well , would it matter if I put the impeller in with the vanes going the wrong way?...............Pat

 

[captddis]

Put them in which way is easiest. They will orientate when it is cranked. It is a myth about having to orient the blades.

 

[Maynard Rupp]

It probably won't make a difference. You could easily tell by cranking the engine momentarily and watching which way the drive pulley rotates. Be careful with lubricants on your impeller. They need to be water soluable. The most popular lube to make that thing slide in easily is KY Jelly. (No pun intended). KY is water soluable but will dry to a sticky jell before the water gets there. If you assemble the pump, note the rotation as above, and rotate the pump's pulley in that direction while the KY is still greasy. Of course you can buy KY Jelly at any drugstore.

 

[mike]

Crankshaft rotation is clock-wise when viewed from the front of the engine.

 

[MikeP]

I just replaced the mains (8v71TIs )and genny's (16KW NL) impellors this morning!

I remove the old ones when I winterize and install new ones every spring. I use vaseline and put the impellors in as Capt said - which ever way is easiest. I just apply the vaseline to the ends of the vanes and smear a bit around the pump bore. Then I twist/push the impellor into the pump until the impellor splines engage with the shaft. I used to compress the vanes with hose clamps but I have found I can do it without so I don't bother. After the splines engage, I push the impellor in by hand. It's not really difficult at all.

I used to worry about the direction of the vanes on installation but discovered that when you pull the cover in the fall, there are always some vanes pointing in the "wrong" direction. This happens because when an engine is stopped, it usually kicks back a partial revolution, driving the pump backwards and reversing at least a couple of vanes. That demonstrated to me that the vane direction on installation is irrelevant. It corrects as soon as the pump shaft rotates.

I'm sure KY jelly is fine for this purpose but vaseline works very well and I always have some on the boat because it's handy for a lot of uses.

 

[Nonchalant1]

Rotation is not always clockwise from the front of the engine. Port engine is opposite rotation from s/b. Also, the pumps can be located on different PTOs and have a rotation different from the crankshaft.

To determine rotation direction of the pump, just look at it. The cam is at the "top" of the pump in between the two ports. The water comes in from the intake (sea strainer) side and goes around the "bottom" of the pump to the outlet pipe side. The direction of the impeller rotation is the long way around from the intake to the outlet. The water does not go across the "top" part of the pump where the cam is. The vanes will be bent so that the outside edge bends away from the cam, and point opposite to the direction of rotation.

DD service manual says to lubricate pump body and vanes liberally with "water pump grease". My local DD service manager says just use regular vaseline. It's not water soluable. If you do use vaseline and your pumps are within a foot or so of the waterline (most are) you don't have to prime the pump when you first fire it up. That sounds like engine heresy, but it's what DD says.

It's true that the vanes will be forced to realign if you put them in bent backwards, but why do it, that way they don't have to realign. A great way to compress the vanes for installation is to use a piston ring compressing collar.

BTW - the torque for the cover screws is only 72-78 in. lbs. (not foot lbs). If you have the screwdriver type bolts, just tighten tight with a hand screwdriver and check for leaks after startup. If you have hex head bolts, be careful or measure it so you don't overtighten.

Doug Shuman

 

[mike]

Initial post stated STBD engine, response was for that motor NOT port. DD engines with Alison trans spin in opposit direction of the props wnen in FWD gear.

 

[REBrueckner]

I have found over the years thjat a change in main engine (8V71TI's, previously 6V53's) impellers at about five hundred hours engine time serves me well. Thats about four or five year intervals. But I usually run at only 1500 RPM.
Last years when I changed first impeller it looked fine and I was annoyed I went to the trouble of changing it. I almost decided not to bother with the second engine,port side but was glad I did: That impeller had two blades with partial cracks along the spline. Might have last another year intact, might not have.

Liquid detergent works just fine for lubricating impeller blades. And of course is water soluable. An antiseize lubricant on the inner spline assures easy removal. Our local DD mechanic also starts up engines with no priming. Given the opportunity, I try to remove the pump zinc plug to check it...and use that access to prime the pump with water for lubrication and improved suction before engine start. Just opening the plug allows salt water to rise back up thru much of the intake...you can feel the air being expelled...

 

[egaito]

Maybe it's overkill, but I don't find it difficult to alighn the vanes, and hold them in place with a zip-tie while I'm installing the impeller.

I agree with using dish soap as a lubricant as well. Saves time cleaning up too cause it's already all over your hands!

-Ed G.