480 MY

[Robf]

All
Been out of Sea Rays for a few years and looking at venturing back in the fold. I am currently interested in a 2005 480 MY. From what I understand, the Cummins engines in this boat have problems with the exhaust overheating as they are "dry exhaust". Can more knowledgeable folks here explain the set up on these exhausts and how they differ from the typical wet exhausts and how much of an issue is this? I have read some accounts of overheating and warping the heads. That can't be good!
Any and all information around this issue and these engines would be appreciated!
Thanks in advance!
Rob

 

[Maybe A Dancer]

watching

 

[ttmott]

All
Been out of Sea Rays for a few years and looking at venturing back in the fold. I am currently interested in a 2005 480 MY. From what I understand, the Cummins engines in this boat have problems with the exhaust overheating as they are "dry exhaust". Can more knowledgeable folks here explain the set up on these exhausts and how they differ from the typical wet exhausts and how much of an issue is this? I have read some accounts of overheating and warping the heads. That can't be good!
Any and all information around this issue and these engines would be appreciated!
Thanks in advance!
Rob

Are you in reference to the Cummins QSM11?

 

[Robf]

Are you in reference to the Cummins QSM11?

Yes,those are the engines

 

[ttmott]

Yes,those are the engines

They are very good engines. The issue was the Sea Ray boats were "over-propped" and loading the engines too much. The fuel burn is too high for a given RPM. The exhaust manifolds which are cast iron would warp away from the cylinder head and leaks develop. When you look at the engines look around the exhaust manifold mating surfaces for soot traces. There are always some but if there is a large amount of soot then the situation needs to be corrected. When sea trialing the boat the fuel burn rate should be close to 17 GPH at 1800 - 1850 RPM - that would indicate that someone has taken pitch out of the propellers which is what needs to be done. I had over 1 1/2 inch of pitch taken out of mine to get there.
There are two different lengths of bolts attaching the exhaust manifold sections to the engine; Cummins issued a Tech Bulletin to use all the same length (the longer) bolts so the clamping forces remained the same across the bolting pattern on the exhaust manifolds as they thermally expanded and contracted. The Tech Bulletin is not mandatory but recommended when the manifolds are removed or replaced.
It's not incidental to pull the exhaust manifolds and rectify the situation. Today I'd plan around $8K per engine to get it done with replacement manifolds and hardware; then the propellers will be around $800 each.

But this is the only significant issue with the engines I know of. They are robust and reliable powerhouses.

This is what excessive sooting would look like; also visible up around the heat shield when everything is installed -

 

[ttmott]

When the exhaust leaks between the cylinder head and manifold the mating surface on the manifold will erode and either require replacement or machining. Mine were in pretty good shape so I surfaced them -

 

[Robf]

ttmott, thank you for the detailed explanation. This gives me what I need to evaluate these boats. At $16k to correct both engines, that will definitely be a negotiating point if not previously corrected!
Rob

 

[ttmott]

ttmott, thank you for the detailed explanation. This gives me what I need to evaluate these boats. At $16k to correct both engines, that will definitely be a negotiating point if not previously corrected!
Rob

This is one of those purchase things that you would want your mechanic to do rather than the current owner having it done. Too many important details that can be ignored and hidden to save a few bucks. Have a reputable Cummins certified mechanic get you pricing then add 20% as negotiation pivot.

Things you will want to do when everything is apart is have the coolers tanked and leakchecked and thermostat replaced which typically would be on the purchaser's nickle.