Engine Rotation

[Jasper]

I have asked this question of people who know their boats and the Detroit Engines, but I am getting a different response from a respected supplier of Gear Box oil pumps.

I replaced both the oil pumps for the gear boxes last year with NEW Hydreco pumps.
At the time, the supplier advised me that I needed one pump to be Counter Rotating.

However, the mechanic here, who has been working on DD and Allisons for many years said they were the same pump both sides.

So I ordered 2 of the same pumps from the US.
They worked perfectly for the last 10 months, keeping the pressure to the GB's at 150 p.s.i.

Until yesterday:
The Port side GB would not give ANY thrust over 1000 r.p.m. I checked the pressure to the GB and it was under 75 p.s.i at Fwd and Reverse. I removed the screen, found some clutch material, I cleaned out the screen and replaced it carefully making sure the gasket was good.

Went for a run and the Port engine worked well, giving full thrust.
But 10 minutes later, the Port stopped giving thrust and I limped home at idle. The Port engine will not give thrust over 1000 r.p.m.

The Hydreco supplier came back to me today and said I should have installed one Counter Rotating pump and this was the reason it has failed.
Yet the mechanic here and my friends in the US say the rotation is taken care of in the Gear Box, not the engine, so the same pumps should be fine both sides.

Your comments would be appreciated.

 

[captddis]

The pump rotation should be the same. If in doubt roll the engine over with pump removed and observe the rotation.

 

[Jasper]

The pump rotation should be the same. If in doubt roll the engine over with pump removed and observe the rotation.

Just about everyone I ask says the same as you, the engines have the same rotation....except the people who sold me the new Hydrecos. They insist that one MUST be Counter Rotational!

 

[bobk]

Sounds similar to what I encountered several years ago. The pump was OK, but the transmissions seals were cracked requiring a rebuild. Last fall I had the port transmission pulled to change the rear main seal and found the seals on that side had also cracked, but were still functioning. Total hours for each was about 4000.

Bobk

 

[saltshaker]

Are you certain it's the pump?

 

[bostonhatteras]

The model number of the engines will tell what rotation, locations of starter and other peripherals on the engine as well as many other details. Look in the dd manual on the first pages for this explanation of the model number. The model number is stamped on the block somewhere above the block skirting around the expansion (freeze) plugs.

 

[Maynard Rupp]

Our Crusaders turn in opposite direction. This was achieved by using timing gears on the starboard engine's camshaft and conventional automotive chain and gears on the port engine. All new Crusaders run the same way as a car. One transmission is run in reverse to make the shafts go opposite. Do all diesels offer opposite rotation engines? What about newer Yanmars and Cummins engines?

 

[Canuck Dennis]

Twin disc transmissions can run either way, usually counter rotating props are handled by one transmission running in "reverse" or, the engine can be counter rotating and both trans. turn to suit.
If you have both engines turning the same way and you want counter rotating props, the transmission has to make that happen

 

[saltshaker]

The pump rotation should be the same. If in doubt roll the engine over with pump removed and observe the rotation.

Listen to Dave, he's worked on plenty and even owns a pair in his boat. I can't give you a definitive answer but logic would make me think the engines have the same rotation. I know my Allisons were left and right gears as noted in the model numbers, M20L and M20R. Since the Hydreko pump is an engine driven pump, I would think the engines rotation is what matters, not the gear. When I replaced mine I don't recall having a left and right pump. I'm no expert on this but Dave, captddis is and I'd trust his advice.

 

[captddis]

Just about everyone I ask says the same as you, the engines have the same rotation....except the people who sold me the new Hydrecos. They insist that one MUST be Counter Rotational!

The engine rotation is opposite with Allisons, but the pump rotation is the same.

 

[Nonchalant1]

The fact that it worked fine for 10 months is a clue. My 1978 53MY's DD 8V71TIs had opposite rotation. You can check the rotation by watching the engine. However, the pump could be set up to be the same. As stated prior, take the pump off and watch the direction the drive turns. If you are finding clutch material in the 3 bolt flange screen, it may be that's the bigger problem and it can re-clog quickly. That's what the screen is for.

 

[Jasper]

Sounds similar to what I encountered several years ago. The pump was OK, but the transmissions seals were cracked requiring a rebuild. Last fall I had the port transmission pulled to change the rear main seal and found the seals on that side had also cracked, but were still functioning. Total hours for each was about 4000.

Bobk

Had the GB pulled back off the engine last year and replaced seals and piston.

 

[Jasper]

Are you certain it's the pump?

Hi Saltshaker,
When I cleaned the screen and replaced it, the GB worked well, then failed about 10 mins. oil pressure drops to 75 psi in gear.
There is oil in the GB, I even added some.
So I am open to suggestions.

 

[Jasper]

Thanks to all for the replies.
I was asked straight up by Diesel Pro for the serial numbers on both GB's and engines when I ordered them last year and again when I emailed them 2 days ago with the problem. They insist I need a Counter rotating pump on the port side?
So, after Easter I will take off the pump, check the rotation of the engine. Also I may swap pumps.
And, bostonharris, I will get out the manuals and see what they say.

 

[Canuck Dennis]

I had an issue with J & T on my 6-71 N's, the serial #'s showed a standard engine cooling water pumps but was actually a high output pump installed, J&T blamed DD and vice versa, who paid ...?? not them..

 

[Jasper]

As expected:
The Port GB serial # ends with an "L"
The Stbd. serial # ends with an "R"

This is on the GB not in any manual because my engines and GB's were replaced with newer models.

 

[captddis]

You are overcomplicating this.
The engines are counter rotating and turn inboard. The hydreco pumps run off of the blower drive gear and turn the same direction. The Allisons are Left and Right as they can not be run in reverse to change rotation like twin disc's.

Also if any metal shavings from the pick up screen make it to the hydreco pump they will trash it.

 

[dsharp]

I was thinking the same thing about trash getting to the pump. I wouldn't try swapping pumps.

 

[Jasper]

I was thinking the same thing about trash getting to the pump. I wouldn't try swapping pumps.

I get that point from you and captddis!
Thanks..... I am going to have a beer or 6, then a nap, before I go to bed!

 

[bobk]

Jasper, I hope you are well rested. Please don't forget to post the eventual outcome.

Bobk
Still lying Port St Lucie but getting the itch to move northward