Cummins QSM11 Turbo Engine

[Flytrade]

I'm interested in purchasing an 07 52 Sedan Bridge with 1000 hour QSM11 dry turbo engines. I inspected the heat shields, and although they appear to be in good condition, I'm concerned about the heat from the dry turbos and the potential problems that it may cause.
Any experience or thoughts on these engines with 1000 hours would be appreciated.

 

[carterchapman]

Lots written about them - a bullet-proof engine with that issue being the only problem. They need to be under-propped so you don't use over 19GPH at 1900 RPM. That keeps the airflow up and reduces EGT. Manifolds, Turbos and gaskets have to be replaced every 5-700 hrs if you are over-propped.

One of the owners will jump in and correct those numbers, but I recall researching it on boatdiesel.com when I was considering a 52DB.

 

[quality time]

Not so much the turbo that's the issue, it's the dry manifold.

 

[fwebster]

Some QSM-11's have shown up with a crankshaft thrust control problem. For some reason the crankshaft moves from front to back too much. This increases the flex in the unsupported "snout end" of the crankshaft and it can eventually break off. The rebuild kit and new crankshaft seems to take care of the problem.

We had one local boat and 3-4 transients show up with broken crankshafts. This was usually on 2003-2005 model boats. Once repaired, the problem doesn't resurface. A good engine surveyor can see the added wear on the end of the crankshaft where it has moved in and out of the seal on the front of the engine.

 

[ttmott]

Besides understand the engine loading the exhaust manifolds are prone to exhaust leakage; which, in a way is due to high EGT's. The heat shields are not necessarily an indicator of a problem unless there are soot traces on them. Look around the exhaust manifold behind the aftercooler for soot tracing; if it is extensive then it will need to be corrected and should be a negotiation position for the purchase price. The EGT issue is high engine loads and fuel consumption between 1700 and 2200 engine RPM due to over-propping (high load on the engine). This is a great writeup on the issue: https://www.sbmar.com/articles/propping-cummins-qsm11-to-prevent-exhaust-leaks/ I added 100 RPM to the props which ended up being about 1 1/2 inch of pitch and the engine load went from 88% to 74% at 2000 RPM; correspondingly, fuel went from around 25 GPH to 18.9 GPH. With all this the EGT's significantly went down which will remove thermal stress on the exhaust system. The real interesting part is the boat's speed didn't change; in fact, it slightly went up but we stripped and repainted the bottom and a host of other things.
To Mr. Webster's point earlier if the front seal is leaking oil and the engine production is in the early 2000's make sure a qualified mechanic and surveyor who are familiar with this issue go over it. For the 07 DB you are looking at shouldn't be an issue.

 

[BeeBoating]

I owned ‘52 2006. PO had to deal with the STBD and I dealt with the PORT. I repitched the props and saw the boat run much better/cooler and don’t expect the new owner to have issues. Fixing the issues (cooler/turbo) was about $6k for the port. Not fun, but given the costs of ownership of these boats not a huge deal. I would have no qualms about owning a QSM powered vessel.