2015 up 30 hp Mercury vs 30 hp Tohatsu

[cchilb]

I know these are the same engines but Tohatsu says it changed its lower unit to 2.17:1 from 1.92:1 in 2015. Mercury still shows 1.92:1 lower unit.
Does Mercury put there on lower unit on these motors? I was under the impression that the only difference was the tiller controls, paint and stickers.

 

[Sea Rider]

Welcome to Iboats,

What precisely do you want to know ? Which is faster, which gear case produces more torque ? Although the 30 Merc is a rebadged Tohatsu model, there will always exist some tech differences between both brands as not to be 100% clone ones.

Happy Boating

 

[cchilb]

Yes trying to decide on prop for the Merc. Bought a used 2016 with no prop. Will be putting on Lowe 140T V bottom. The boat loaded will be in the 1200 to 1400 pound range. I am thinking with the 1.92:1 ratio I want a 9.5 pitch 4 blade to get the motor in the 6000 to 6200 range hoping for 24 to 28 top speed. The 11 pitch on the 2.17:1 would be about the same. Not sure the 1.92:1 can turn the 11 pitch fast enough.

 

[Sea Rider]

Generally speaking you should dial a prop that makes combo to rev around middle to max wot rpm range as usually loaded, but going full wot rpm is best, independently of the gear ratio. As this is not rocket science will need to put a prop as a starter for a water test and go from there maximizing props to run at max wot rpm if in need.

Happy Boating

 

[Texasmark]

If you want to know your gear ratio, remove your plugs and your cowling. Mark a line on your flywheel and your prop for reference to fixed objects. Turn the prop in one direction and pay attention to the amount you turn it as you observe your mark on the flywheel. When the fly wheel mark returns to it's starting point, check how far your prop turned......a protractor (simple device for measuring angles....Dollar General has them for a buck). If your gear ratio is 2:1 the flywheel will turn one full revolution with your having turned the prop two full revolutions.....so 360 degrees for the flywheel and 720 degrees for the prop = 2:1......360 (degrees of flywheel rotation/X degrees of prop rotation is your ratio.

So if you have the 1.92 you won't get to the full 2 revolutions of the prop when the flywheel completes it's circle. If you have the 2.17 the prop you will complete the 2 revolutions and barely get started on your 3rd.