Mercury conversion from 40 to 60hp.

[Chris Cole]

Hello forum,

I am wondering whether a conversion from a 40 to 60 hp is a good or bad thing. I have a 40 hp merc 2000 3 cylinder 2 stroke. Before I owned the motor it was converted to a 60hp. It looks like the carbs are for a 60 and the reeds are for a 60. Everything is the same in the 40 and 60 except the gear ratio, for a 40 it is 1.83:1. For a 60 it is 1.64:1.
What concerns me is the WOT water pressure of both the 40 and 60. For a 40 at WOT the specs say you should get 5-7 psi. For a 60 it is 7-12 psi.

My question is:
Do you think I am getting 60 horses out of this motor with a 40 hp gear ratio?

Do you think my motor will run hot?

Any help is appreciated, thanks.

 

[Texasmark]

Re: Mercury conversion from 40 to 60hp.

Looks like they dropped down from just 50 and 60 hp on the 52 cu in block and picked up the 40, dropping the classic 4 cyl.

That sorta says that temp shouldn't be a problem as you have all the passages necessary to handle the 60.

The change in gear ratio is between the driveshaft and the propshaft. With the engines rated at 5000-5500 rpm's the prop shaft, which contains the water pump, is turning at the same speed in the two engines.

All that says you should be ok. additionally you have an overtemp alarm if you get into trouble.

You might go to a Merc dealer and compare the part numbers of the thermostat, poppet (pressure relief), and impeller. If the same, ask the mechanic what the difference could be....could have made a special lower unit for it since it entered the market late (Classis 40 was in it's place). But it doesn't seem cost effective to design and build a special lower unit for one engine of a series........but the gears are different....so who knows.

Since it's a smaller engine, the lower gears would help it push harder.

Mark

 

[Chris Cole]

Re: Mercury conversion from 40 to 60hp.

Thank you, I appreciate the response.