2009 VMAX HPDI 250 Running Slower after Gear Lube Change

[willfb0002]

So I bought a Ranger Z520 new to me in August this year, and it has a 250 HPDI on it. So far it has worked fine, pushing the ranger to 75 mph in October.

One day I noticed that the prop had some line wrapped around it and decided to change the gear lube - water came out. So I got it serviced at a dealer who just replaced the seals since the gears on the LU looked fine. The mechanic put high performance mercury quicksilver in the LU, and I am not sure what was in it before.

Now I cannot get the boat over 70 mph. Anyone else ever have this issue where changing the gear lube slows the boat overall? Any chance changing to Yamalube will help me out here? Could this be indicative of a bigger problem?

Note: I have a Fury 26 pitch for the prop and everything looks fine with the prop... no dings or nicks.

[boscoe99]

New gear oil is more viscous (thicker). Mercury gear oil is known to create more internal friction. Also, the newer seals are gripping the propeller shaft a bit more tightly. More drag. This is preventing the propeller shaft from turning the RPM that it once was.

My next best guess would be "hell if I know"! I don't even know if you are using GPS for speed, a paddle wheel or a Pitot tube. Into the wind or down wind. Fresh water or salt water. Ambient air conditions.

[willfb0002]

I've used two different GPS units for speed. Fresh water, going WOT in pretty much all directions on multiple outings.

Thanks for the info... I had thought about the gear lube being more viscous, but not the prop seal gripping more tightly! So does anyone think the Yamalube or Hypoid gear oil will make a difference?

[99yam40]

Who realy knows for sure.

You can change it and see if it makes a difference and then post back what you find out.

Did WOT RPMs also drop?

[willfb0002]

Yeah I am only running about 5400 at the moment. Before I was 5700 or so.

Any idea who carries the hyoid gear oil they recommend in the manual?

[FabricGATOR]

Are you by any chance loaded any heavier than before? Carrying more ice and beer? More fuel, bait, has the third mate gained a few holiday pounds?

[willfb0002]

The captain has gained a few holiday pounds! Not to the point I think it would affect anything however. She has 1 new battery that is a 29 group replacing a 27 group, and a humminbird 360 bow mount transducer on the front now...

Probably didn't add but 20-30 pounds total. I had been able to run 72 no problem in the summer with 2 people in the boat, and 69 with 3 people, so I doubt it is a weight issue.