PDQ OWNERS FORUM

We just suffered a serious exhaust system failure & a hydrolocked engine (water in the cylinders) which could have been “fatal”. I suggest you check this on your engines!
PDQ apparently added a flange between the turbocharger & the exhaust elbow, likely to change the angle down to the lift muffler. The only problem is that the flange is attached with steel machine screws & are not likely to be checked or replaced, even by someone replacing the exhaust elbow. 2 of the 3 screws (not the studs you see - the machine screws are between the flange & the turbocharger) corroded in half, causing the angled gap you see in the photo above. This allowed exhaust gases to leak out & the lift muffler to fail (the exhaust gases are what forces the water out of the lift muffler & overboard). Once the lift muffler is full, the exhaust water has no where to go, except into the engine cylinders. Bad.
It is EXTREMELY difficult to extract broken steel studs corroded into cast iron with no room to work. It took us 3 days & even had to make our own temporary flathead machine screws (we are in the Bahamas). To add to the fun, you need to remove the fuel injectors & turnover the engine to extract the water.
Our engine is fine, but could have been catastrophic, requiring a major engine rebuild.
Whether yours look angled like photo or not, I would strongly recommend pulling yours apart & replacing the machine screws (unless you know it’s already been done). This could be a 1-hour job…or a 1 - 2 day job if already broken off or just corroded in place.

Ours on both sides have corroded within the past several years. It was a tough job getting the broken fasteners out. High temps and salt water injection make this inevitable. Thanks for posting the warning.

We had the same issue about three months ago. Two of the three bolts had corroded and snapped. We did not have the exhaust water backup. To work on it, I removed the exhaust elbow and turbocharger together. It took a lot of heat to extract the broken screws.

Alan

pdq must have redesigned the elbow in the later years because our elbows look nothing like the picture. i assume the brass plug is zinc anode. we don't have that or the 2 web re-enforcements. i assume the problem studs are the ones which hold the elbow to the turbo.

james power may have some insights on what changes were made over the years.

This what the machine screws holding the flange to the turbocharger & the gasket look like after 16 years.

Thanks for the heads up! Can you tell us the screw size/type/material and also the gasket part number. We are hull 102 so probably not far behind you. I took a look today and didnt see anything obvious but its all blind so no telling what lies beneath!

Thanks,
Doug

Doug-

I believe they are: Metric socket flat head, class 12.9 alloy steel, 8mm x 1.25 mm x 25mm. They were black oxide coated, but I’m going with zinc plated for more corrosion protection - stainless might last longer, but the alloy steel is supposedly nearly twice as strong as stainless. Boltdepot.com has them with reasonable shipping.

Unfortunately a gasket won’t work for me anymore unless I remove the turbocharger & have the mating surface machined - the heavy rusting pitted the cast iron, plus I slightly nicked it with all of my dremeling to extract the broken screws. Permatex says their Optimum Red Gasket Maker will stand up to the job.

I also plan on using the Permatex between the flange & the (new) exhaust elbow - I’m not crazy about the large countersink for the flathead screws - that leaves even less than 1/4” of sealing surface.

Russ is right with the screw size. I used stainless but I really don't know which screw type is best. I did remove the turbo. I don't think I could have removed the screws with the turbo in the boat. Even with it out of the boat, I could not get it hot enough to get the screws out with a propane torch. I took an acetylene torch. My turbo and one side of the spacer were quite pitted. My neighbor has a metal lathe so we resurfaced the spacer and used a wheel to smooth out the turbo. I was able to seal it with a cut it yourself heavy duty exhaust gasket. A lot of work but the turbo got a good cleaning while it was out. I plan to do the port side in the fall if it doesn't fail between now and then.

Alan

Final report:

I would NOT recommend a high temp gasket sealant. When I took apart my temporary repairs, the sealant had failed & was all “gummy”. Permatex makes another higher temp sealant, but the temp rating is only slightly higher - I wouldn’t trust it. In the end, I used Yanmar style metal gaskets (from HDI) when re-installing the spacer flanges & with new HDI stainless exhaust elbows.

On my other engine (no problem visible) I spent a week with penetrating oils, tapping & every type of wrench - the 3 screws to the spacer flange would not budge so I am leaving as is. The screws were shiny stainless & apparently solid. It appears this engine has already been re-done, as the screws weren’t steel & the exhaust elbow was of different design?

The weak link seems to be the combination of metal gaskets & steel screws into the spacer flange. When the gasket begins to corrode, moisture gets to the steel spacer screws & corrodes them as well, until breakage & failure.

I don’t have any solid recommendation for inspection/maintenance. While removing the exhaust elbow is pretty easy & “safe”, attempting to remove the 3 screws to the spacer flange could be opening an expensive can of worms. On the other hand, a failure like I had could be even more expensive…

hi russ,

did the failed bolt shear even with the face of the turbo or the face of the spacer?

Flush with the face of the turbo - which made the 2 broken ones extremely difficult to extract.

Russ - thank you very much for posting this !

Here's the report from Hull #29: The prior owner replaced both Turbo's in 2020 (Thanks Bargain Bill !).

The starboard screws came right out, but it looks like the old gasket was reused with some red Permatex, and it was shot. Mastry had the Yanmar gaskets in stock 129472-13520.

The port screws are stuck ... used heat and all the tricks in the book, and can't get them to budge. I've got this on my list for next winter, to pull the turbo and get it on the workbench... we'll see if she makes it till then.

Following up on the last post -

I pulled the port turbo, got it on the workbench as Alan suggested, and got nowhere.

I took it to a small auto engine shop, and they were able to remove the screws. They put A LOT more heat on it than I was with the little torch.

There was no corrosion, but I'll sleep better at night knowing that it was checked.

About 100 hours after Shearwater installed our replacement engine our spacer backed off the turbo. I believe the screws were not the correct ones because the heads did not sit flush with the face of the spacer which allowed them to back out a bit causing an exhaust leak. Fortunately, the exhaust occasionally sprayed the exhaust alarm collar and the alarm periodically whimpered alerting me of the issue.

Chris-

Glad you caught the problem in time! The screws were likely correct, but I believe the adapter PDQ came up with had the screws holes way over countersunk. That also only left a tiny bit of mating surface left around the screws.

“Can’t think of everything” - when PDQ came up with their adaptor to alter the angle to the exhaust, they likely didn’t consider the possible ramifications years later.