Has anyone seen this problem in an SD22 or CN4-33?

[Tom Young]

My CN4-33 (SD-22 marinized version) had an odd condition. When I had the front pulley set at TDC, I could rotate the crankshaft about 5 degrees right or left without the timing gears moving (IP was pulled).

Also, on rotating the engine by hand, each time I past TDC, I got a slap like sound.

In tearing the engine down (I'm swapping it with an SD-22 in the thread below), I removed the pulleys and nut. I found the cup like washer in and odd condition. In two pieces, it appeared to be held together with some rubber like adhesive(?) This fits over the outer Woodruff key. (The cup is not in the photo)

But when I pulled the timing gear off the shaft, I could see what was causing the 5 degrees of play. The Woodruff key (in the photo now removed and placed on the shaft to show the wear) had worn the keyway to near double size. The key itself had worn into a pivoting like shape. I can't believe it's held together.

Has anyone come across this problem? What do you think may have caused it? One mechanic speculated the keyway may have been oversized at build. (74',...?) Another person commented it could be poor design for the forces.(I've never seen it mentioned here)

I've owned this engine for 10 years and run it seasonally in Maine in our boat. It's always smoked a bit (I can see why now) but has run smoothly. Lately, it's been rougher idling but smooth under power.

Sadly, the rest of the engine, including cylinders (there was no ridge or noticeable scoring), looked pretty good.

[asavage]

AFAIK, the key does not maintain the position of the gear after assembly -- it's merely an assembly aid. The clamping force of the crank nut acting o the sheave and gear does that job. It is torqued to 239 ft/lbs. If that nut is not that tight, the sheave will work on the crank.

No, I've not seen this on an SD before, but I certainly have on other engines, notably the Hillman 1390cc engine, where it is a very common problem.

[steven.0424]

did engine make any type of noise when running to indicate this problem besides the noise when turning by hand what made you decide to pull engine apart to find the problem

[davehoos]

its a very common problem.some newer cars often release modified balancers,or change design of washers ect.

It is torqued to 239 ft/lbs

is very tight and often hard to do without locking the flywheel.

most of the time it obvious how the nut/bolt was left loose[oil seal or timing belt].sometimes it is the metal quality in the shaft or balancer/cog.

the key on this photo has moved and worn as would be expected.I have replaced shafts that have twisted when removing the nut/bolt and on our farm mazda T4100 a punch test found the metal too soft to regrind.a new crank was very cheep.

I had a suzzy gti swift towed in with the eratic timing,with the flywheel locked you could rotate the balancer untill it snapped off the shaft to allow its replacement.

[Tom Young]

did engine make any type of noise when running to indicate this problem besides the noise when turning by hand what made you decide to pull engine apart to find the problem

As this was likely a growing problem, I can't say the engine was sounding differently Steven. The biggest change last season was a rougher idle which probably means it was getting worse, quickly. However, it ran like a top at speed.

The mechanic from Jesco hasn't heard of this. I plan to send the photo to them. He mentioned problems, as Al infered, with removing the main bolt, switching pulleys, etc., can cause problems. I get the sense from the bend of the washer around the nut, some silicone and nicks, and the fact the nut came off fairly easily, someone had done some work on this area before me. Also, a second heavy alternator was mounted to a third pulley when I bought the boat.

I don't know if the SD is the same as the CN but the outer sheeve on the CN has a taper cut into it that recieves a cone type washer that presses into this taper and clamps onto the shaft when the main bolt is tightened down. My only question is, can this cone lock the outer sheeve onto the shaft before it clamps the timing gear tight?

At any rate, I'm glad I didn't have to remove this nut from the SD as I was able to use the factory pulleys. I use one high output alternator.

There's a simple test for this condition; remove the IP timing gear cover, turn the crank to TDC, then see if there's any play at the timing gears as you rotate the crank back and forth a few degrees. I know now, there shouldn't be any.

Note; Steven and others, this is part of the process I'm outlining in swapping an SD-22 from a 720 PU with a CN4-33(the marinized version of the SD-22) from my sailboat.
The thread is; "I sure was glad to find this site,..."

[Tom Young]

Having talked to a very experienced mechanic and engineer (in these things), he offered what he thought the cause was.

My CN4-33 was fitted with three sheeves on the crankshaft end. These ran; raw water pump, small alternator and engine water pump, and a large frame high output alternator. My guess is the large frame alternator was added about mid life to this 24 year old. It also ran a larger width belt.

He felt this engine may not have been designed for the extra side loading that may come with these extra pulleys. Specifically, he said, if the large frame alternator was not perfectly aligned, slipping belts can cause overtightening of the belts. These plus the extra leverage from the length out of extra sheeves can cause problems.

He also said it's a fairly easy thing to check with a stationary pointer. At different rpms and loads check to see any play in these sheaves that may indicate over stressing. He recommended buying more belts instead of over tightening, especially if 3 or more sheaves are installed.

He said it's not uncommon for industrial, especially marine engines to receive added loads off the end in alternators, refrigeration pumps, etc. that they were never designed to handle.

[Tom Young]

Having talked to a very experienced mechanic and engineer (in these things), he offered what he thought the cause was.

My CN4-33 was fitted with three sheeves on the crankshaft end. These ran; raw water pump, small alternator and engine water pump, and a large frame high output alternator. My guess is the large frame alternator was added about mid life to this 24 year old.

He felt this engine may not have been designed for the extra side loading that may come with these extra pulleys. Specifically, he said, if the large frame alternator was not perfectly aligned, slipping belts can cause overtightening of the belts. These plus the extra leverage from the length out of extra sheeves can cause problems.

He also said it's a fairly easy thing to check with a stationary pointer. At different rpms and loads check to see any play in these sheaves that may indicate over stressing. He recommended buying more belts instead of over tightening, especially if 3 or more sheaves are installed.

He said it's not uncommon for industrial, especially marine engines to receive added loads off the end in alternators, refrigeration pumps, etc. that they were never designed to handle.

[rlaggren]

To a limited extent the "extra" loads can be balanced using brackets that put similar side loads opposite each other (more or less). I guess he's saying that the pulley loads caused the crank to flex and that allowed the key to shift around.

However, to my mind it still sounds more like an installation problem where the keyed sprocket was not secured properly and could shift, causing the key to carry the driving force to that sprocket. My understanding is that the key itself is not actually designed to carry loads, but to locate the sprocket positively during installation.

Rufus

[Tom Young]

To a limited extent the "extra" loads can be balanced using brackets that put similar side loads opposite each other (more or less). I guess he's saying that the pulley loads caused the crank to flex and that allowed the key to shift around.

However, to my mind it still sounds more like an installation problem where the keyed sprocket was not secured properly and could shift, causing the key to carry the driving force to that sprocket. My understanding is that the key itself is not actually designed to carry loads, but to locate the sprocket positively during installation.

Rufus

You could be right Rufus. In my CN4-33 installation, most of the lateral load was to one side. This included both alternators but the large frame with a 5/8" belt was outboard. When Chrysler marinized the SD22 into the CN4-33, among other things, they started with a turned, stackable pulley system on the front end of the cranshaft. The first pulley is closer to the block than the SD22 (the reason for the different waterpump hub). This allows three or more pulleys to be bolted on.

Chrysler then had to have the brackets built for both the alternator and raw water pump. I have found both these brackets to be a little sketchy, strong enough but not easy to get a proper alignment.

Of course then an added large frame alternator fitted for higher charging capacity, requires another mounting system. At this point, it's not likely any engineering is involved.

As a consultant, he's been hired to trace similar installation problems with other boats. In one case of a high end boat, the loads were so strong that the shaft was snapping off several boats. A class action lawsuit followed. It turned out that the extreme side load added was not properly engineered for the engine. Another course of taking power off the engines had to be devised.

At any rate, I'm now using the more simple factory pulleys on the SD22 with good success. The alternator mount is a much better set up, closer to the block with a shorter belt and very strong and I had no problems getting a good alignment. I no longer use the large frame alternator as my charging requirements are filled by this small frame 90amp. This, btw, was mounted just below the small frame alternator on my CN4-33.

The other pulley runs the raw water cooling pump. It's not as well aliigned as I would like (not that great a mount) but the load is small.