Getting my 1st 300R V8 this week.

[Capt.Insane-o]

Randy, be safe. That motor actually looks pretty good on the boat.

Looks waaaay better than a Verado on there.

[LakeFever]

Looks Awesome! Man I'm super jealous of you guys today.

[2jz]

Very excited to hear test results, comparison between two stroke and four stroke.

My money is on four stroke because of bigger displacement. I say 107mph today

[Chaz]

Looks waaaay better than a Verado on there.

Agree 100 %

[Instigator]

Agree 100 %

Agreed buttt, a Force looks better than a Verado ��

[WILDMAN]

SOMEONE needs to start their own thread if they want to post crap that has nothing to do with this topic!

Anyway, we spent 6-7 hours at the lake today. Lots of issues, but it worked out OK at the end of the day. This 21 ran 100-101 with the 300xs. Of course we are at 90 degrees and 100% humidity which does not help. First, we did not realize that the motor is limited to 4k rpm for a while, then 5k during breakin. While taking turns driving around the lake for two hours, it started pouring rain and 30 mph winds and whitecaps for about an hour. Once the rpms kicked in, we were out of gas and had to drive 10 miles to get more. Then, once back in the water, every prop we tried hit 6400 at only 90 mph. Even a 36" cleaver. Turns out that running the motor as high as it needs to be just makes the props slip like crazy. Even lowering the motor 3/4" didn't help. Finally I tried the 15.25 x 34" Max 5 prop. I had it on the 400R 21 Liberator. The first pass ran 96. 2nd pass I bumped the trim and ran 97. We then raised the motor about 3/8" to 2 3/8" above the bottom and ran 103 at 6050 rpm. I guess you just need a big diameter prop to work on these gearcases. Just takes time to figuer it out I guess. Mercury says there's another 4-7 mph with the right prop. MAYBE THEY CAN LOAN ME ONE TO TRY HINT,HINT.HINT!! I know they are reading this! I think the boat is sold, so I need it ASAP. HINT,HINT! Another issue we had was that it would not go over 3700 and was running rough. Turns out one plug wire came completely off. My fault. I took it off to check compression for someone and must not have gotten it back on tight. Overall, once we got everything working, the motor does pull very hard even with the 34" 5 blade. The motor is pretty quiet when in the water and even when on plane. It's louder to people outside the boat. Sounds alot like an I/O boat from a distance. Overall, I think it's a big improvement over the 300xs and has alot more power in it than is available now. It will take some time for people (and me) to figuer out the setup. Once we figuer it out, It will be worth the change. As it is now, it's 2-3 mph faster on this 21 Liberator. Hopefully, I will get to borrow the correct test prop before this boat leaves here and I can report the full potential. Again HINT,HINT!! I forgot my camera, but I know Joe and Zo6man got some video and pics so maybe they can post them.

[oldschoolltv]

For boats of this size it looks like a great motor, I just wish they made one with a 15 inch mid, Hint Hint

[speedinstream]

Ol 2 smoke hard to beat !!

[xb03fs]

Thank you for the write up. First performance boat it’s been on to my
knowedge.


it will suck to have to buy all new props. Hopefully a bigger promax prop is made soon...

[Greg G]

Thanks Randy for taking the time to post real data after the three of you went through a frustrating day for sure.

[mach351]

Thanks Randy sounds like we have a winner! Can’t wait to see the Vids

[LongShot]

Makes perfect sense that the big diameter cases are going to need way more diameter props and perhaps a slightly thinner profile to keep the torque from the 4 stroke from wanting to make the prop climb. Maybe on the larger boats and especially a non-pad boat the stern lift might not be a problem. I remember the first record runs made with the 2.5 Sportmaster on 20' pad boats resulted in a blow out at normal propshaft height. They finally figured out with the props on hand they needed to hide the case by jacking it up. If memory serves they ran it at 60 mph and kept raising the motor until it ran out of water pressure and locked it down there. Sounds like Randy is finding some of the same issues. It'll run....just needs the set up massaged to get there.

[engineermike]

I posted this a few days ago, "I think with the hd sportmaster, very high x dimensions, and the torque output increasing, we will see the popularity of 5 blade props increasing."

I had the same experience with very high slip numbers until I switched to 5-blades.

[xb03fs]

What are thoughts on a big diameter 4? I know they don’t exist at the moment

[engineermike]

What are thoughts on a big diameter 4? I know they don’t exist at the moment

The bravo1 is 15 1/4 and it was complete poo on my boat (hd sportmaster). Meanwhile, the 15" max5 was awesome. 15.3" Maximus was ok, but even still you can have too much blade area. I don't think it's a diameter thing as much as it is about optimizing blade area.