1993 Evinrude Ocean Pro 150 conversion to 175

[rhp5033]

Hello,

This is my first post, I recently acquired twin 1993 ocean pro 150s that were in rough shape. I managed to salvage one complete motor by swapping good parts onto one of the motors. Now I am left with a slew of parts that would be a shame to waste, so my question is has anyone ever done or heard of anyone turning a 150 into a 175? I could easily rebuild to make another 150 for spare, but I thought it might be a fun project to convert it to a 175, also if its successful then I have a 175 with a 150 spare.

I have researched it quite a bit, and the blocks are the same, and from browsing the parts catalogs, I found the only difference appears to be the carb body assembly and the throttle bodies. My motors are plain Ocean Pro 150s so I am not talking about a 150 fast strike which is very similar to the 175.

Does anyone know what the specific differences are between these parts? are the carb bodies only different because of different jets/orifices? what is the difference between the throttle bodies? is it possible to modify the 150 throttle body to be a 175?

Are there any other parts that are different that I should be concerned about?

I appreciate any input and advice.

 

[Faztbullet]

Block the same ... exhaust port timing is different.

 

[jimmbo]

A lot of people think changing the jets and/or a twist of a screw will raise the HP of an engine. No, there are differences between two engines of the same displacement that are rated different HP. Some differences are easy to see, others very subtle. To make more HP, it needs to turn higher rpms. It needs to breathe better.
The jets will be different as well as the air bleeds, however to make 25 more HP the engine will need to inhale more air and fuel, so the bores of the carb will be larger to let the extra air thru.
Exhaust tuner/megaphone is different too, all part of helping the engine exhale better, and utilizing exhaust tuning for more power. The 175 exhaust is tuned for a higher rpm range than the 150s

 

[rhp5033]

Thanks for the feedback, more than likely I will just rebuild as a 150 for spare powerhead / parts. I was just curious if it was feasible and possible to convert it to the higher HP, and what the actually differences were between the parts mentioned.

Thanks again

 

[jimmbo]

With all the correct parts, the engine can be converted, but you have to make sure all the parts that are different are changed. In some cases, even little things like the throttle linkage had some different parts between the different ratings.(that linkage difference was one many between 90 and 115 mercs in 1984-85.)

 

[Faztbullet]

If you want to make it a 175, just get the carbs and throttle bodies,cylinder heads and have the exhaust ports raised .125

 

[bob johnson]

funny how the parts diagrams and listings say a part will interchange with various other motors....the motor family you have is a prime example and ive found out first hand what the truth is. Evinrude.com will say themselves on their site a part "fits" another motor, but the reality is..."it may fit" but it doesnt belong!...ie...yeah it BOLTS UP>...i see rebuild shops list 150 and 175 as the same rebuilt block???? ha ha.... the exhaust port openings are different shapes and or in different spots IN THE BLOCK between a 150 and a 175...so how could they possibly interchange????? i did this job on a 60 degree 90 hp and turned it into a 115 hp... i had to measure the opening of the ports in a 115 i had, and i used a foredome tool to grind the opening in the 90 hp block to match....but luckily i had a 115 already in hand!...... i doubt you could find the specs on the exhaust port openings of the 175 any place! ha ha ha...in the V6 series they have a motor called FASTSTRIKE for johnson and INTRUDER for evinrude that has more hp than listed and revs 500 rpm higher.... i have yet to find out what specifically attributes the extra HP..... all the parts"interchange" with the other v6's........