[bdunigan]

Today I wrapped up the pulley mod to correct the misalignment that was causing belt chirp & snap. The first pic is the Dayco laser alignment check of the factory pulley. The 2nd pic shows the misalignment of the factory pulley…one full groove or 3.5mm.  The 3rd pic is the modded pulley with shows near perfect alignment. The 4th pic shows a detail f the modded pulley. In short, 2mm was milled from the outer race and 3.5mm was milled from the inner flange surface. No more noise. I checked the stbd pulley at it was off by 1/2 groove or 1.75mm. This causes very minor noise at cold idle and the noise goes away after warm up. The stbd alternator is factory original. Like the port side, the crank pulley and fan hub lined up perfectly. So, if there is a lesson here, it is that the QSB6.7HO alternator mounting and tensioning system is subject to lateral variation that can cause these alignment issues. Mine was simply worse than most.

[bdunigan]

Thanks, Tony. I am having the pulley machined to correct the misalignment. When it is ready to be installed, I will take pics…before and after….and post. The pulley mod will solve my problem. Just soooooo weird that this misalignment exists without clear reason. I removed the mounting bracket on Sunday and saw no issues or possibility of lateral movement. It came out and reinstalled without issue. So if the bracket is the issue, it has to be a factory machining fault (if I understand your comment correctly).

[bdunigan]

QSB6.7 425HP, SN: 73430746, 725 hours

Tony, the alternator I replaced with your 22si unit was the original 4003445. Your replacement alternator is SKU: ALT-22SI-130-3 and it has the Cummins 3918275 pulley. As far as I am concerned, yours is a direct replacement and is not the issue.

I didn’t take any pics yesterday while I was diagnosing the issue with the Dayco laser but the alt pulley was out of alignment (too far forward) by one groove or rib. I wish I had taken photos. 

I don’t believe the alternator was installed incorrectly since, even though the pulley was off by one groove, the laser line was parallel to the pulley groove. There was no ‘axial’ or ‘angular’ misalignment that would indicate a mounting issue since the laser line was not at an angle to the pulley groove.  That said, I could be wrong. The mounting bracket is fixed with locating pins so there is no variability there. The alternator ears that straddle the mount leave no room for forward or backward play. IOW, the there is no way to move the alternator further back to get the pulley lined up correctly.

Over the next week or so, I will have to remove the pulley and have it modified. At that time, I will take pictures and post. I will report back then.

Thanks, Tony, for your response.

[bdunigan]

Rob, Tony:

Thanks again for your time and input. Very, very helpful!

[bdunigan]

Rob, it is the pic angle. I’ve attached a better one. The static water line is 13″ below the bottom of the elbow where it attaches to the turbo exhaust flange. Water does not sit in the elbow or hump hose but does sit in the horizontal portion of the frp tube that runs to the pod…pic attached.

Re 90 degree elbow. I pulled this pic as an example of a bonded elbow. DeAngelo built the elbow for this SeaRay exhaust system. I don’t have any info on engine, boat model, etc.

[bdunigan]

Tony:

I just spoke to DeAngelo and they provided additional info. They said, ‘If an elbow is bolted to the turbo exhaust flange, it does not need to be bonded as it benefits from the bonded engine. If a SS component is placed between two non metal components like hump hoses, it needs to be bonded.’ The picture in my earlier post displays this.

Don’t shoot the messenger!

[bdunigan]

Thanks, Tony, for your reply especially at the late hour. My elbow is pictured below (3281) and has no bonding wire. AFAIK, Sabre doesn’t make this a practice.  I have attached a picture from a larger SeaRay system that I found on ClubSeaRay.com. It seems SeaRay, in some cases, does run a bonding wire to the SS riser or elbow. Of course, everyone I have spoken to including a marine electronics company that is reconditioning my bonding system has NOT heard of this practice. Nevertheless, two different ‘account managers’ at DeAngelo made this recommendation. The only thing I can think of is DeAngelo wants to protect the weld joints.

BTW, I fresh water flush after every run (thanks to you guys) so I am not too worried about salt water corrosion.

[bdunigan]

Thank you, Tony. I will use ‘zero’ load as the standard. The water level at the dock is 13″ below the bottom of the elbow at the turbo exhaust flange. Tested this in the past. Not ideal but at least better than the 12″ minimum (if I have my facts straight).  I don’t think the water level gets up into the hump hose. Rather it sits in the FRP tube. In the attached photo, the water level is 2-3″ above the top of the strainer.

[bdunigan]

The elbows pictured here are 316 stainless as far as I know. The replacements DeAngelo build for me last season are AL6XN. Is that the same as INCONEL?

[bdunigan]

The dock water I use for flushing is well water and runs cool….say 60 degrees or so…if not a bit cooler. My seawater is 85. Coming off a run, the engines, of course, are sitting around 155-160. Certainly the after coolers and heat exchangers are not this hot but they are very warm to the touch. I would guess maybe 120-130 but am not sure. So, in a matter of 5 minutes, the flush process cools these components roughly 60-70 degrees (if I have my temps right). Maybe I shouldn’t be concerned but thought I would inquire.  

I guess I am worried about ‘thermal shock’ which I am told is defined as rapid heating or cooling by 18 degrees F per minute. So, doing the math, cooling these components by 90 degrees in 5 minutes could be bordering on thermal shock. Of course, I don’t think I am cooling them this much so maybe I am OK.

[bdunigan]

Brad, I like your idea but would have to see it in action. There are plenty of videos re saltaway for outboards but I haven’t seen anything for diesels like ours. I would also have to get some kind of endorsement of this process, a how to guide, and some assurance it works and doesn’t cause any issues. 

[bdunigan]

I may add the deck fitting later as I improve the overall system. For now, a hose goes to each strainer. These hoses are led through the aft engine bulkhead into the pod bay where they tie into a y valve. A single hose goes from the y valve to the dock. When not in use, that hose is simply stowed in the port cockpit lazerette (still connected to the y valve). To flush, I need only extract the hose and connect to dock water.   

[bdunigan]

OK, here is an update. I bought a water pressure gauge and a water flow gauge. Using these, my dock water pressure is 60psi and pumps 15gpm…plenty to handle the 10gpm my QSB6.7 units demand at idle (600rpm). Once I plumbed 30′ of hoses, y valves, etc to the flush valves, I still had 13.5-14gpm. I used 3/4″ hose. My sense is that I am pumping more fresh water than the engines demand and the excess is going out of the open intake. A ‘taste test’ of the exhaust water is totally fresh water. I was concerned about putting too much pressure into the Groco strainers (plastic bowls) so I called Groco. They calculated that, with the intakes open, 15 psi at the flush valves translated into 7 psi in the strainers….way less than the 30 psi it takes to crack them.

 

[bdunigan]

Thanks, Steve. I plan to do a test as soon as our marina dock water is turned on. I also plan to test with 25′ of 5/8″ hose as I suspect the flow is reduced proportionally to hose length and ID. I may also test with 3/4″ ID hose. I will also measure the gpm intake rate of the engine at idle using the bait tank method to see how fast the engine ingests a given amount of water (with seacock closed). I want to use the ‘seacock open’ method in the future and hope my fresh water feed will meet or exceed the gpm demand of the pump & 27000K impeller at idle. 

[bdunigan]

Thanks, Gene, for the reply. On the 6.7, the sea water pump pulley goes to a smaller idler pulley. However, the idler is driven by the much larger crank puller so I suspect both the sea water pump and the alternator run at higher rpms than the engine itself. Not sure though.

[bdunigan]

Tony, thanks for the quick reply. I am amazed you are ‘online’ on a Sunday evening! Wow!

I will run the ‘out to sea’ test you have prescribed sometime this week and report back.

I will describe my typical usage as follows: My cruising area is the Chesapeake Bay and the ICW down to Hilton Head, SC. The majority the time, seas are less than 1′. Rarely do I see anything greater than 1.5′-2′ seas. My runs are ‘continuous’, point to point, no stopping, no floating/fishing….just cruising to that day’s destination. I run at 65-75% load and no greater than 29gph. I will occasionally go to WOT for testing purposes. As a rule, I come of plane very slowly. There have been perhaps two occasions over the last 300 hours where I had to pull power quickly. Only once have I run in serious trailing seas of 2′-3′ and was at cruise power during the run. Hope this helps.

No response required until I runtime ‘out to sea’ test.

Again, many thanks!!

[bdunigan]

It looks like I did delete a post although I am having some trouble with the system. Here is the deleted post….

“What exactly (some engine symptom or ?) brought on all the questions and concerns about the exhaust flange connection ID?”

During a 500hr service, my tech identified leaking exhaust elbows. My Sabre 42 is a 2013. He had recently replace an exhaust elbow on 2014 Sabre 42 (same engines as mine…QSB6.7 380hp). The replacement elbow was ordered from DeAngelo who supplied the originals to Sabre. My tech noticed that the elbow gasket that came with the replacement elbow was smaller than the flange on the turbo. The elbow gasket was 3″ ID and the turbo flange was 3.5″ ID. He found this odd but completed the repair using a QSB6.7 3.5″ gasket

My tech mentioned this discrepancy to me when he identified my elbow issues. I contacted Sabre who sent me the drawings for the original elbows. These drawings and DeAngelo confirmed the original specs from Sabre and Cummins called for a 3″ ID elbow flange. I questioned Sabre who stated that the sea trial data for my boat was ‘within spec’. IOW, the exhaust back pressure was acceptable even though the elbow flange was smaller than the turbo flange. Note: my Sabre 42 is the first with the 6.7 380hp engines. The prior 42s had the 5.9 380hp engines which I believe have a 3″ ID turbo.

So Sabre and Cummins put a 3″ID exhaust flange against a 3.5″ turbo flange. By my calculation, the area of a 3.5″ circle is 9.62 sq in. The area of a 3″ circle is 7.1 sq in. In essence, that equates to a 2.52 sq in road block of the exhaust exiting the turbo or basically a 25% restriction. Maybe this doesn’t matter to a 6.7 380hp unit. Maybe the 3.5″ turbo was designed more for the 425/480/550 hp 6.7 units. I really don’t know.

I had DeAngelo make the replacement elbows with a 3.5″ flange so they matched the turbo flanges.

I have the engineering drawings for the original elbow from Sabre if you want to see them.

Note: The picture of my turbo was taken immediately after the elbow was removed. There is gasket material still on the turbo flange. As you can see, the gasket is the graphite version. We installed the metal version during our repair.

[bdunigan]

It looks like I did delete a post inadvertently. Here it is….

“What exactly (some engine symptom or ?) brought on all the questions and concerns about the exhaust flange connection ID?”

During a 500hr service, my tech identified leaking exhaust elbows. My Sabre 42 is a 2013. He had recently replace an exhaust elbow on 2014 Sabre 42 (same engines as mine…QSB6.7 380hp). The replacement elbow was ordered from DeAngelo who supplied the originals to Sabre. My tech noticed that the elbow gasket that came with the replacement elbow was smaller than the flange on the turbo. The elbow gasket was 3″ ID and the turbo flange was 3.5″ ID. He found this odd but completed the repair using a QSB6.7 3.5″ gasket

My tech mentioned this discrepancy to me when he identified my elbow issues. I contacted Sabre who sent me the drawings for the original elbows. These drawings and DeAngelo confirmed the original specs from Sabre and Cummins called for a 3″ ID elbow flange. I questioned Sabre who stated that the sea trial data for my boat was ‘within spec’. IOW, the exhaust back pressure was acceptable even though the elbow flange was smaller than the turbo flange. Note: my Sabre 42 is the first with the 6.7 380hp engines. The prior 42s had the 5.9 380hp engines which I believe have a 3″ ID turbo.

So Sabre and Cummins put a 3″ID exhaust flange against a 3.5″ turbo flange. By my calculation, the area of a 3.5″ circle is 9.62 sq in. The area of a 3″ circle is 7.1 sq in. In essence, that equates to a 2.52 sq in road block of the exhaust exiting the turbo or basically a 25% restriction. Maybe this doesn’t matter to a 6.7 380hp unit. Maybe the 3.5″ turbo was designed more for the 425/480/550 hp 6.7 units. I really don’t know.

I had DeAngelo make the replacement elbows with a 3.5″ flange so they matched the turbo flanges.

I have the engineering drawings for the original elbow from Sabre if you want to see them.

Note: The picture of my turbo was taken immediately after the elbow was removed. There is gasket material still on the turbo flange. As you can see, the gasket is the graphite version. We installed the metal version during our repair.

[bdunigan]

I completed the ‘water level’ test as described above. This test was ‘at the dock’. Attached are two photos. The measurement from the bottom of the elbow to the water level in the clear tube is 12″ which I understand is a ‘minimum’ requirement. This doesn’t give me a lot of faith in the design. Comments?

[bdunigan]

I agree that the Sabre/Cummins logic is flawed and that their back pressure measurements were lowered by the restriction. In fact, during our sea trial after installing the new 3.5″ elbows, turbo boost at 3000rpm was 2-4 psi higher. At WOT (3050 rpm), turbo psi hit 29 psi which is right were the actuators start to open. In past tests, the WOT turbo psi was closer to 25-26 psi. While I didn’t experience a significant increase in WOT rpm (maybe 20 rpm), the boat felt better.

Should I remeasure exhaust back pressure to ensure it is still below spec? I understand that 5 in hg is maximum. During the original sea trial by Sabre in 2013 with the smaller elbow flanges, they saw 3.3″ port and 2.8″ stbd.

Do you think removing the exhaust restriction would cause exhaust back pressure to exceed 5″?

[Author]

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