6-71 Raw Water Pump belts

[brettportzer]

This may be a really dumb question, but my Detroit manual doesn't have an info on it...

I want to change my raw water pump belts, and, it doesn't work like the alternator where there is an obvious way to tension it.

I think that the way to do it is that there are 4 bolts holding the water pump down and then there are two bolts with nuts on them that you adjust to loosen or tighten the belt...

But before I dive into trying to get those loosened, etc, I thought I'd ask if that is how it is actually done!

Thanks!!

[Captain Ralph]

Gee, your raw water pump is NOT directly mounted on the end of your engine and direct drive?

[brettportzer]

Nope.

They are 1972 J&T 6-71N.

Everything is mounting mirror image.

Raw water pumps are outboard on bottom front of engine, two belts from the crankshaft.

Alternators are outboard on top rear of engine, one belt, and more sort of usual style of adjustment for the belt.

Here is a photo, if it is visible down there on the bottom left, there are two bolts that seem to me to be the adjustment.

SBRawWaterPump.jpg

[Captain Ralph]

Wow, It was a few years ago I had witnessed this before. Did not realize this is by design.
Just been plugging along since, working on mounted DDC/Jabsco pumps.

As long as I'm learning new things, can you offer an idea why they were not directly connected to the back of the block. Something else back there?

The first 6-71Ns I worked on and managed for a few years were sweet and spoiled me. The raw water pump and alternator were direct drives on the back of the block.

[brettportzer]

No idea, the Detroit manual I have suggests that it should be a direct drive, but my understanding is that there are different ways to outfit these engines and especially the cooling system, which is part of however J&T decided to marinize them?

It is handy that everything is mirror image, I suppose, and maybe that has something to do with it.

[jap201]

if you have the engine s/n's, your can give J&T a call and they should be able to help you.

[Captain Ralph]

No idea, the Detroit manual I have suggests that it should be a direct drive, but my understanding is that there are different ways to outfit these engines and especially the cooling system, which is part of however J&T decided to marinize them?

It is handy that everything is mirror image, I suppose, and maybe that has something to do with it.

Oh the straight 6s are great for mirrored installs. As on the boat I mentioned, Detroit just rotates the block around end for end. Now you have counter rotating, exhaust manifolds mounted out side, starter and blower mounted inside and the same for the ancillary equipment..

The 6-71 is my favorite DDC engine.
AND, I'm still learning about them.
Thx

[brettportzer]

Still learning about mine for sure...

Starters are outboard, alternators are outboard, raw water pumps are outboard.

Blowers are inboard, I think the oil coolers are inboard, fuel pumps are inboard.

Not sure off the top of my head regarding everything else.

[Scarlett]

Check and see if there are shims under the pulley on the pump. Had one where you added or subtracted shims to tighten or loosen the belt