I know some guys here tried to test a XB-21 with a 300R and 1.60 gears but, the lower kept blowing out. My question is how many RPM were you able to turn it and was the test with a full Load? A fella around here has a new XB-21 300R with 1.60 gears and can only turn a 28 pro max 5500 rpm. This full gas TX load with power poles.
How many hours are on the motor? Could still be a break in thing. Even with that, I would go smaller than a 28 with that kind of load.
I took a 28 promax up to the limiter on my boat. It still couldn't beat the 32 Promax with 1.75's. Data to data the 300R 1.6 couldn't out gun my 300XS DBR 1.62, and didn't beat the same motor with 1.75's.
I didn't walk away impressed with 1.6 gears.
Allison XB21 2+2
Mercury 300R
I dont really know them they reached out to me to see if i had a prop they could try. I have a 26 Pro Max I told them they could run I asked them if they were getting full throttle because that just didnt seem right to me. I think it also struggles to get out of the hole. Any how I posted this out of my own curiosity not even sure they know anyone with a XB-21 to help them out or if there are even any around. I ask where he bought it and I think he said macon Ga. I actually taked to his son and not him. He did mention they had some sort of throttle problem when it was new and they had it adjusted and it ran great for a while. I am not real sure the info I got is real acurate just going of memory and a one conversation.
The new throttle can be difficult. It is important to test multiple times and make sure it repeats. It really seems like a good starting point for them to look further at. Despite the load and age, the RPM does seem low.
This post and one in the motor section reminded me to post on the testing we did. I will get another post going on that.
Allison XB21 2+2
Mercury 300R
I told him about BBC hopefully he will reach out and maybe find this thread and we can get him straight.
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