QSB480 Wastegate Paint Burning

[John Albaum]

Hey Guys,

Finished my repower and while doing some sea trials found that the paint burned on the wastegate during WOT. The engine is a 5.9 QSB480 and WOT specs are 3450RPM, 1.5psi exhaust back pressure, 94%load, 25ish GPH, a little over 800 degrees exhaust temp, and just under 36 pounds of boost. Just wanted to check and see if this was normal for the paint to burn.

On the plus side the boat cruises comfortable at 2800 rpm, 15gph, 70% load making 22kts!

Topic

[Tony Athens]

Somewhat normal..

I’d be thinking 3″ of pitch.. This engine performs best when it literally zooms up to 3480+ RPM and the load at WOT is at 92-95% or LESS. ………..We shoot for a 10% buffer at 90% , leaving about 45 HP on the table at WOT. Set up like that, the boat will just jump up on plane.

Tony

[John Albaum]

Hey Tony,

By no means was I thinking there was more power to get out of the engine, I’m was planning on pulling a little more pitch out of the prop because the boat wasn’t fully loaded during sea trial. WOT was only for testing and seeing what the RPM, fuel burn, and EGT was. I was just trying to see if the paint burning was an issue I needed to be concerned with or if it was somewhat normal.

Thanks
John

[Tony Athens]

Just a coule of thigs..

You seem to think that you have some room left as to HP…Trust me, you do not..You are for it all ++…………You are actually over propped where it REALLY matters if you look at the published power curve for your engine.. WOT is meaningless unless your plan on running there for anything but testing……. –It’s all about cruise HP/GPH.. At 2800 rpm you should be at 13.7 GPH or less..

As to burning paint– the load you are putting on the engine will do that.. Ask less and it will burn less………..Ask more and it will burn more..

Tony

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