1987 200 Black Max powerhead on 150 lower

[dsiekman]

I recently purchased an old Hydra-Sport 21' center console (kevlar) with a 1987 Black Max 200. I understand that the lower was replaced with the lower from a 150. From my research I have found that the ratios were different. The 200 was 1.87:1 and the 150 was 2:1. The motor has a 23p prop. Here's the question: I am planning to repower this winter, but I don't want to get stranded out there. What sort of trouble should I expect from this setup? Do I need to keep an eye on the tach to avoid over-revving? Will the extra HP shred the gears? Will it be a dog? I'm having a hard time wrapping my head around this. Thanks!

 

[dsiekman]

If I did the math correctly, the max potential speed with the 2:1 gearing is about 61 while the 1.87:1 gearing would be about 65 (less slip). That doesn't seem like a huge difference to me, especially when either of those is too fast for cruising around with my 4 y.o. to go fishing. That is at an assumed max rpm of 5600.

 

[Chris1956]

OK, I think the question you are asking is how do I keep from breaking the motor this year? Is that correct?
l​ doub't there is any real difference between the gearcases of the two motors, beyond the gear ratios. I would baby the motor a bit, so the strain on the gearcase is less.

For example, if the prop leaves the water when the water is rough, I would cut back on the throttle so the prop doesn't have to bite the water at full throttle.

 

[dsiekman]

Thanks, Chris, yes, that is pretty much what I'm asking. The majority of the area I'll be fishing is limited to 35 mph, so the likelihood of leaving the water at full throttle should be pretty low. I usually run my stuff pretty conservative anyway, so hopefully it won't be an issue.

 

[Faztbullet]

The 2:1 ratio will given it a better hole shot as motor spins up faster and there is about 6mph difference in speed at WOT. No difference in toughness between ratios

 

[dsiekman]

Great! Thanks for the info!