I had a terrible thing happen this spring lower unit replacement. I had smaller gear case and the new one has a larger gear case(guess Mercury had problems with endurance with the smaller one). I have a 1991 Ranger 361v with a 150 Mercury XR4 Black Max. Previously I was running about 63mph can't recall wot rpm. I put the old prop on 23p Turbo SS which goes to a smaller gear case 58mph @6100rpm. Local dealership says wot rpm should be between 5500 and 5800 and suggest the lower side due to the age of my engine. They have a 23p Tempest Plus (larger gear case) and said it may work to get the rpm down because it is larger gear case. I borrow it and get 60mph @5900rpm. I know that engine height plays in this but it is at the same height as before and the reviews I read say Tempest is one of the best and still not getting the same speed as my old gear case and turbo prop. I am considering 25p Tempest or maybe a 24p Fury but I am weighing my options. The price is big for these and I am not sure is worth it. Nobody has a used Stainless larger than 23p and no one does loners within 50mi. of me. Several marinas have said the 23p tempest is the way to go but I don't have the same speed as before and my rpm is too high. Which is why I was considering motor height could be the problem.

What prop do you suggest? brand and pitch and do you consider it worth the money?

What motor height should I be at? I have a 6" jackplate.

Thanks for the help!

Zach

A good starting place for a Ranger hull is center of the propshaft 3 1/2 inches below the pad ..... how is your holeshot and H2O pressure ??

I'm running a 24p Trophy on my 150 mercury, so don't be afraid to go on up. You never know until you try one. Just watch your water pressure guage if you start jacking the motor up.

A dealer should let you take them out and run them before you commit to buy. At least the ones here will.

Water pressure around 15 with the 23p tempest @5900rpm wot. Prop shaft center is right at 3.5" below bottom of the boat when parallel. My hole shot is solid.  I have asked around and no dealer is willing to loan props, one said I could buy and then return but he doesn't carry higher pitches. Plus once you find the right one they would want you to buy from them. I have found the Tempest for $399 online and the Fury for $479.50 they have I believe all the Mercury props for a lot less.

Sounds like .... if you are at 3.5 inches that you need more pitch .... 1 inch pitch should drop you about 300 rpm ..... consider sending your prop to Marks High Performance props ..... tell him what the numbers are now and what you want to get to. He will balance and blueprint your prop .... repair any imperfections and tweak the prop to your wishes .... it will be the finest running prop you will ever have. Many people send new props for a Balance and blueprint. He can work majic !!!

Mercury has a try it before you buy it program for their props. Their website has a lookup page that will show you the dealers closest to you that are participants in the program.

I'd be very surprised if your 150 could turn a 24p Fury, usually you drop down a pitch for the fury. Are you sure your new LU has the same gears, it sounds like to me you may have different gears in your new LU and that's what's caused the difference in speed. Nothing that cant be fixed by repropping though.

AT 3 1/2", you could stand to raise it a bit.  Go in 1/4" increments and watch your water pressure and tach.  A relatively large jump in either means you went a tad too far, so keep accurate measurements and be ready to back it down to the previous location.  You'll then have your sweet spot.