Will 120/140HP 4cyl drive fit 165HP inline six boat?????

[Fordiesel69]

Original 165HP drive is shot. A friend has a good 120/140 he will sell me. Will it fit a 165?

This is a 1977, and I belive it is an MC1 (before alpha 1.)

 

[dubs283]

Re: Will 120/140HP 4cyl drive fit 165HP inline six boat?????

if the splined shaft is the same length it will fit

but...the gear ratio in the drive is wrong

 

[Fordiesel69]

Re: Will 120/140HP 4cyl drive fit 165HP inline six boat?????

Is gear ratio in the upper or lower half?

How can I tell what the gear ratio I have currently?

 

[Pete104]

Re: Will 120/140HP 4cyl drive fit 165HP inline six boat?????

The ratio is in the upper. If the 165hp drive is shot, how? No oil? What makes it shot?

 

[dubs283]

Re: Will 120/140HP 4cyl drive fit 165HP inline six boat?????

Is gear ratio in the upper or lower half?

upper

How can I tell what the gear ratio I have currently?

the only way to absolutely positively know the gear ratio is to pull the upper apart and count the driven and drive gear teeth

the ratio of an UPPER ONLY for a 165 hp in-line 6 is 1:1 - (e.g. 24 teeth/24 teeth)

there is a chart in the OEM manual for determining gear ratio and what gear ratio is need for which engine - mercruiser designates OVERALL drive ratio for this (total ratio = upper/lower ratios combined)

 

[kilowatts]

Re: Will 120/140HP 4cyl drive fit 165HP inline six boat?????

Hi Guys:

I think the answer is: yes it will fit but it's the wrong gear ratio in the upper half. You need a 1.65:1 ratio for an inline 6 so you can either swap out the gears (much work) or get a good used outdrive with the right ratio. I have heard of people who do use the wrong ratio on their outdrive and make up the difference with their propeller setup. I don't really understand how that works so I stick to the OEM specs. I hope this helps.

kilowatts

 

[Fordiesel69]

Re: Will 120/140HP 4cyl drive fit 165HP inline six boat?????

Ok, I tried it and yes it works fine, BUT the engine is too powerfull it seems for the speed I am going. I will research it is cheaper to source another drive or up the prop a bit.