Mercury CNC props Bblades MRI scan
 

I'm tracking down a lower RPM issue and need to rule out the props. They are Mercury Racing CNC 17.5" 39P 18R 1500HP rated. They are on my Hustler with twin diesels and #8 Arnesons. Getting on plane there is about a 300 RPM difference and running at speed about 150. I've had the injectors tested and switched sides so they are ruled out. Obviously changed the filters and such in the fuel system. Starboard motor the one that has lower RPMs also burns more fuel and runs more boost at the same RPM, 3 more gallons an hour and 2 more psi on boost. It also shows more load, about 15%. Drives feel smooth and tranny's run same temp. Boat only has 250 hours and the previous owner put the props on right before I bought it so not much data. I don't have any experience with these props, can they be that different being "CNC"? Plan is sending them to Bblades for their MRI scan and test again on labor day weekend when I get back on the water. Any experience with Bblades? They said two week turn around. I can't afford to not have them back before labor day weekend. She gets put in storage Sep 15 for the winter.

check to make sure your trim settings are the same.

That was my first thought. With a level and a tape they are the same. If I trim the starboard up a almost two points they run the same but can make it chine walk. On the trailer is very obvious it's trimmned way up compared to port. I'm leaning towards props. If not I guess this winter we'll have to sort it out. Motors are basically still new, as far as diesels go.

If you have that short of a season and can deal with the RPM difference and fuel burn, I'd icebox it till the winter. Enjoy the summer and have a winter game plan.

Problem is I really need to eliminate the props from the equation. Otherwise I'm kinda stabbing in the dark. If the props check out then I'll pull all the injectors and compression test the motor and have the injectors full serviced. We only did a pop off test on them the first go around, kinda a sore subject. They are 2 stage injectors so they were only able to test the first stage. I'm really hoping it's the prop.

They are throttle by wire and I don't believe it will go 100% in reverse. It's only $150 for the prop MRI. Also, trying to dock her would be interesting like that. Lol I don't want to be YouTube famous.

Side by side and tails are exactly the same.

Don't try this. You will smoke your trannies.