20 hp Props

[fishinwrench]

47 minutes ago, Basfis said:

Any time you can use the same casting across pn’s it saves a ton of $. Often allows same machining fixtures, shared tools and such. At the scale of evinrude, easy to imagine the cash savings being in excess of $1m on a single share starting at the foundry thru inventory. 

 

Exactly.  A lot of block castings are identical across several HP ranges.....but if the finished product has the same part# then that means cylinder porting is the same as well.    HP differences in that case would be merely intake and exhaust related, gear ratio, and probably different ECM programming. 

Which brings me to the question of why anyone would chose a 15hp over a 25hp (same weight, same paint job, same price....or it SHOULD BE).  

[snagged in outlet 3]

2 minutes ago, fishinwrench said:

Which brings me to the question of why anyone would chose a 15hp over a 25hp (same weight, same paint job, same price....or it SHOULD BE).  

Guys do in hp restricted areas.  But other than that, no reason to do it. 

[3DHUSKER]

Fuel system is what is different between my yamaha 40 and a 50.

[fishinwrench]

2 hours ago, 3DHUSKER said:

Fuel system is what is different between my yamaha 40 and a 50.

I don't think so.   What year class?   I'll see if I can look it up.  

A brief look between 1987-2002 shows different exhaust housing, different pistons, and even a different spark plug. 

[rumrunner]

Outboard HP is rated at the propshaft +/- 10%. So why do you need to compare kilowatts? More cubic inches generally means more torque to get moving. A lower pitch prop accomplishes the same. Just curious what you are after?

[aarchdale@coresleep.com]

On my last boat i had the 75 Optimax and had the computer flashed to 115.  It made a huge difference, the motor came to life. Only thing i had to do was pull a restrictor out of the intake.  the 75,90, and 115 were pretty much the same from what i understood.

[fishinwrench]

2 hours ago, aarchdale@coresleep.com said:

On my last boat i had the 75 Optimax and had the computer flashed to 115.  It made a huge difference, the motor came to life. Only thing i had to do was pull a restrictor out of the intake.  the 75,90, and 115 were pretty much the same from what i understood.

Which # is said "restrictor ? 

[aarchdale@coresleep.com]

# 17 on the throttle body diagram

[3DHUSKER]

4 hours ago, fishinwrench said:

I don't think so.   What year class?   I'll see if I can look it up.  

A brief look between 1987-2002 shows different exhaust housing, different pistons, and even a different spark plug. 

Yamaha 40 hp 2 stroke 1998 

My Yamaha factory service manual is for 40 and 50 and the carbs are only thing different. Same pistons, same crank, same everything. I don't give a flip but it sure is interesting.  Lists out all the specs right beside each other. Pic of one of the pages attached.

[fishinwrench]

15 minutes ago, 3DHUSKER said:

Yamaha 40 hp 2 stroke 1998 

My Yamaha factory service manual is for 40 and 50 and the carbs are only thing different. Same pistons, same crank, same everything. I don't give a flip but it sure is interesting.  Lists out all the specs right beside each other. 

Yep you're right.  The 55hp looper is where the bore/piston change occurs.