The differences between a 135 and 150 optimax

Bgbbgb246

Seaman Apprentice
Joined
Jan 28, 2019
Messages
38
I looked around the web for the differences between the 135 and 150 Optimax as i hard that they were almost the same motor being manufactured out of the same block. There was some good information like the fact that the gearing is different in the lower end (135 is 2:1 and 150 is 1.87:1), they have different ECU's, and they might have different intakes. However, everyone was unsure if there was or wasn't any other differences. So i decided to go through the parts list for each motor and see if i could find any additional differences. I can confirm that the gearing and ECU are in fact different. However the two motors share an intake with the difference being a "gromet" that reduces the airflow of the 135. The 150 has a much less restrictive "gromet." Additionally, the "exhaust extension" seems to be different between the two motors.This part i am unsure about the differences and the effect of this part. maybe someone can help me here. Other than this i just thought i would add some information to the topic since i could not exactly find definitive answers to my question on the forum sites. Attached are the pictures of the parts list with he non-matching parts highlighted. feel free to add anything i may have missed if you have expertise in this topic
 

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Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,930
Pretty sure there is a difference in porting as the sleeves to repair block are notched and different part numbers
 

Bgbbgb246

Seaman Apprentice
Joined
Jan 28, 2019
Messages
38
Pretty sure there is a difference in porting as the sleeves to repair block are notched and different part numbers

Certainly could be! The heads and block are both the same part numbers so I'm not sure why the repair sleeves would be different.
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,633
Port Timing and or Width, probably cause the Blocks have different ports

The difference with the Exhaust Extention, that is the Exhaust Tuner. 2 strokes often use the Pressure Pulse of one Cylinder to push the Air-Fuel Charge that is escaping from another Cylinder back into the Cylinder. Since sound does travel at certain speed, the different Lengths of the Extensions will change the RPM where the Tuning takes place/occurs, customizing it to a particular engines Torque Curve
 
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