Decoder Ring for Gray Marine 6-71 DD engines

In one of my other posts you can read of the demise of my new (to me) boat's two 4-53 DD installed during a 1970's re-power.

This gives me the opportunity to go back to 6-71's as it happens I have located two running and reasonably priced Gray Marine 6-71's.

I would like to know a bit more about the engines but can't find much info on how to decode the model numbers and serial numbers for these gray marine engines. Does anyone have the decoder ring.

Example - port engine is model number 64HN9 and serial number is 132067. Oddly enough these numbers are stamped on a Gray marine plate mounted to the top of the gear box??? Should the numbers not be on the engine?

Any help is appreciated.

 

64HN9

This was the high output large injectors advanced timing WWII landing craft engine.

We have one and it works fine at more modest outputs in a 50 ft USN Utility boat..

IF the engine has not been run in a while , you MUST remove the valve cover and be sure none of the injectors are stuck.

Rebuilt injectors are about $45 each .

The old USN WWII training manual is fantastic at showing all the info needed for these engines.

ON line used.

 

Hi Fast Fred,

Do these have a 2 valve head or 4 valve head? Can they be "hot rodded" for a bit more output? My goal was $300hp up from what I think was an original power rating of 265hp??

What do you consider a "modest output"?

Thanks so much for the help!

Leo

 

DD 6-71 with mistery transmission

Hi Fred
Is there any chance you can help me identify the maker / model of the transmission bolted to me DD6-71? I looked thoroughly and was not able to find and tag / plates or mfg. info on the housing. The only readable markings are V-9105 on the tyranny top cover and 9092 on the housing onto of the output shaft.
I posted some pictures on the link below:
http://s27.photobucket.com/user/Cezar_Petrela/media/20140812_172853_zps885b289d.jpg.html

Thanks in advance

 

To me it looks like the X8708 it will have a 3.05 or a 1.51 reduction , two piece housing and long countershaft seperiate propeller flange, air cooled

the X8708A is the same but with a short countershaft with built in intergal prop flange.

The tranny requires 5quarts of 50 wt non detergent oil.

I suggest to do any work you find the Students Manual for Grey Matine engines.

3rd edition was from about 1943 , all are 2 valve heads.

235 HP is the high power version , yet will easily go 10,000 hours with maint and ONLT CF II diesel oil.

Hop it up and it can be shot in 1/10 the time..See JT for 450 HP at 30 GPH /1000hours

About 180 HP will last almost forever , with the correct 2 stroke lube oil.

CF II oil , Shell Rotella T in 40 wt has the proper rating

 

Thanks Fred

Thanks Fred.

I am digging around for the student manual now and I'll also look for the transmission manual.

After doing some repair on the ribs of the boat, and getting a look at how old the girl is, I think I'll leave those engines at the stock horsepower. No need to race around and break something that sinks her

Thanks so much again.

I'll post pictures as soon as I make some progress.

Leo

 

There were trannys mafe in that era with 4 numbers that start with 9 ..., but none I could find with your numbers.

Gave you tried Google? Grey Marine transmission and then your number set?

 

A little trick, that I use on DD engines is to put a pair of the round jaws vice grips on the injector rack shaft. If anything is wrong in the governor, you can control the injectors and not let the engine run away. It especially works good on old engines that haven't been run in a while.

 

Please see the attachment

 

Well! That didn't work. Here's a copy/paste of my last attempt. Sorry about the formatting

Series Inline 71 Model Description Chart and Serial Number Location
Application, Rotation and Design Variations
1 06 5 - 7 0 01
Series clys app basic design model#
Inline 71 designation arrangement variation

Application Designations
1062 - 7001 Marine
1063 - 7001 Industrial F to F
1064 - 7001 Power Base
1065 - 7001 Generator
1067 - 7001 Vehicle F to F
1068 - 7001 Vehicle F to F
*
Design Variations
1062 - 7001 4 Valve Head "N" Engine
1062 - 7101 2 Valve Head Engine
1062 - 7201 4 Valve Head "E" Engine
1062 - 7301 Turbocharged Engine
1062 - 7501 Customer Spec. Engine
1067 - 7701 Constant Horsepower
Basic Engine Arrangements
Rotation: L (left) and R (right) designates rotation as viewed from the front of the engine.
Type: A-B-C-D designates the accessory arrangements.



Drive Shaft Rotations


* * * * * * * * * 1122 - 9001 Right-Hand 1122 – 0001 Left-Hand
Shaft rotation on multiple units is determined from the rear of the unit.

The engine serial number and engine model number is stamped on all inline 71 series cylinder blocks as shown below. The engine serial and model number is also printed on the option label attached to the valve cover. An example of a Series Inline 71 serial number is 06AXXXXXXX. The engine serial number is required when placing a parts order.
Model number 1065-7001 is interpreted as follows: Inline Series 71 Engine (1), six cylinder (06), generator set (5), right-hand rotation with "C" accessory arrangement (7), four-valve head "N" engine (0), and specific model variation Number 01 (01).

 

>A little trick, that I use on DD engines is to put a pair of the round jaws vice grips on the injector rack shaft. If anything is wrong in the governor, you can control the injectors and not let the engine run away. It especially works good on old engines that haven't been run in a while.<

The problem is on engines that have not been run, one or more injectors freezes in place and only rebuilding the injector will un-stick it.

If the injector is out of idle position , so is every other injector on the engine.

Buses have air gates to block the intake ,for emergency shutdown, on a boat it tales a STOUT piece of plywood to shut off the air supply.

That is why the drill is to purchase a new valve cover gasket and SEE the injectors actually move before attempting to start an oldie.

DD sells a preserving oil to run thru the injectors to stop this , but its seldom used.