QSB 5.9 Performance

[castlem26]

I operate a 44′ Armstrong catamaran that is powered by 2 Cummins QSB 5.9s. The port engine was blowing antifreeze out of the exhaust and the boat was taken in for service.

The mechanic found a cracked exhaust manifold on the port engine, broken head gasket and the turbo bearings to be worn out.

The shop replaced the head gasket, machined the head surface, replaced the head gasket and the turbos in both engines and the boat was put back into service.

After the service the boat speed has reduced from the low 20 knot range to the mid teens. SBEX Seaview displays show the boost pressure to be 10 – 12 psi down from 15 psi range.

I’m looking for some thoughtful advice on getting her back up to speed.

 

Topic

[castlem26]

QSB 5.9 engine photos

Here are some pictures of the engine before and after the service

[castlem26]

Performance

Thanks for the reply.

The engines have about 8,000 hours on them with no records of service. The mechanic’s thought is that the turbo failed because of wear on the bearings which created too much back pressure. Because of the excess pressure the exhaust manifold failed.

 

The turbos were replaced in both engines. The starboard turbo was showing signs of wear but there was not near the amount of “movement” of the turbine shaft as there was in the port turbo.

[Tony Athens]

IMO, you need to go back to the basics.

1. Total hours on the engines before this “failure”
2.  Why did this happen is what needs to be answered?
3. Both turbos?

Got some pictures of the exhaust system and what is attached to the turbos?

 

 

[Author]

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