Volvo D4 WOT Drop-off

[Dcsqatar]

I have a 2020 R29S with a 300 HP Volvo D4 with about 400 hours. I have tracked wide-open throttle (WOT) over the years as a measure of engine health. Since new and for 4 years in the Pacific Northwest, WOT was always around 3610 rpm. Last year I shipped my boat to the Chesapeake Bay. After a full engine service over the winter, I put her in the water in March. I recorded WOT of 3580 rpm on 30/May and then it continued to drop all season to a low of 3410 on 10/Oct. There also seemed to be a drop in efficiency (e.g., NM/gal). In the PNW, I had routine hull cleaning by divers, but was unable to arrange for that service here on the Chesapeake. What is experience with WOT drop off in general and linkage to hull marine growth in particular? Attached are three photos of my boats hull when recently pulled from the water for winter storage. Doesn't look like much growth to me.

Thanks in advance for any help.

 

[AGLyme]

I asked my Marina owner the same question re my D4. He strongly suggest that I get the prop reconditioned and take some pitch out of it. I’m at 3,300 and have a 31cb.

 

[Martin610]

I have a D4 260. I definetly saw improvement after I had the prop reconditioned. My mechanic had a tough time getting it off.

Since its been 12 years I'm having the bottom soda blasted. I think that will make a difference too.

-martin610

 

[Dcsqatar]

I asked my Marina owner the same question re my D4. He strongly suggest that I get the prop reconditioned and take some pitch out of it. I’m at 3,300 and have a 31cb.

Thanks. What exactly is prop reconditioning? Is it possible to determine need for/value of doing by inspecting the prop? What should I expect, and any idea of cost? Is this something I can request from outfit providing engine service, or do a I need to look elsewhere.

 

[OverTime]

I always thought it was a good idea to remove the prop and clean, lube the spline at least once a year during haul out?

 

[Martin610]

Most marine mechanics can do this work if they have prop pulling tools.

Props can get out of spec with very light grounding, or even just use under load. I don't think anyone can eyeball it. It's good to get it off once in a while to make sure you can get it off god forbid it gets mangled.

I paid 280 dollars to have it reconditioned last time I did it.

-martin610

 

[Maggie Anne]

A prop shop will have pitch blocks for pretty much any propeller. They can use them to see if your propeller blades are within specifications and if bent then adjust them back into shape. A bent blade can certainly account for reduced efficiency and rpm.

 

[Cutwater28GG]

even with diving my WOT drops over the life of the paint. definitely WOT drops due to a dirty hull

also don't forget weight on the boat. fuel, water, gear, people.