QSC-600 prop issue

[Zach Babcock]

We have had concerns that our 2008 Sea Ray 47 Sedan Bridge isn’t propped correctly. Not sure what direction to go with this as we are new to addressing prop issues. Below is the data I collected at the end of last season.

All gal/hr

RPM Port Starboard Spec # from cummins
600 0.6 0.5
800 1 0.9 1.2
1000 1.7 1.5 1.8
1200 2.7 2.4 2.8
1400 4.6 4 4.1
1600 6.8 6 5.7
1800 10.9 9.8 7.7
2000 14.1 12.7 10
2200 17.2 15.6 12.8

Specs are from the cummins spec sheets on this site.

Any thoughts on what the issue is would be appreciated and how to address this. We only have data up to 2200 rpm. WTO is 3000.

When we purchased the boat we had props adjusted due to port not meeting rated RPM. That issue has been resolved.

I added engine fuel burn data as an attachment as well

Topic

[Rob Schepis]

Zach Babcock wrote:

Rob,
On the attachment I don’t see an axis to plot fuel consumption. What am I missing?

Right, on the Quantum engines they dropped the curve of RPM vs GPH that was provided with the mechanical engines so you have to work with the data provided below the graph. Plot your GPH at the RPM’s listed in the chart and comparing that to the printed GPH will tell what is needed to be told..

[Zach Babcock]

I will get a full set of data when the boat splashes in April and repost then.

Rob,

On the attachment I don’t see an axis to plot fuel consumption. What am I missing?

[Rob Schepis]

You want to accurately add your data to the attached graph and chart, the more data you can chart and plot the more accurate the interpretation will be

[Tony Athens]

Data needed: Good GPH #’s from 2200-3000+ RPM,

Tony

[Zach Babcock]

Thanks

What data will be required to better determine what needs to be done with the props?

Any suggestions for a prop shop and or location to purchase new props from?

[Tony Athens]

Looked this over—————On the surface it appears you are quite over propped.. The steady state GPH in the 1600-2000 RPM range is not where you should be operating if the boat is not on a clean plane……………As to what to do??–Without good GPH #’s from 2200-3000+ RPM, I could not with any certainty tell you what to do to the props……..

But I can tell you this– your engines need to reach a solid 3065 RPM at WOT, and REACH it easy while consuming less than 32 GPH per engine, when you are at max load if you want the best possible performance, fuel economy and maximum life out of you engines.

Tony

[Zach Babcock]

Fuel filters are visually clean – under a 80 hours since last replacement but will be replaced this spring

Running gear is good – no growth or build up.

I didn’t get boost readings.

We will be back in the water mid/late April. Is more data required to properly understand the issue?

Are there any shops that you can purchase new props from and send back the ones on the boat? Trying to avoid launching the boat then pulling it back out and letting it sit for a week plus once the season starts.

[Rob Schepis]

Well if she’s over the hump and on plane at 2,200 and still well over the spec GPH she does appear to be over-propped where it matters. You said that was end of season data – what was the condition of the boat bottom and running gear when those numbers were recorded – clean or ??. What about the fuel filters, were they all fresh or ?? Fuel filters in need of changing can disturb the displayed fuel burn. Did you happen to record boost numbers?

[Zach Babcock]

Normal cruise is 2450-2550

We are on plane at 2200

[Rob Schepis]

Those fuel burn numbers indicate you are propped heavy but is the boat even over the hump at that rpm? What is the on-plane cruise rpm where the boat seems to settle in nice on a clean plane?

[Zach Babcock]

Prop MRI's

Here are the MRI scans of the Props post repair for low RPM on port side

[Author]

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