: 150 optimax upgrade to 175


Neb_ProV
06-27-2011, 09:02 AM
Is there anyway to upgrade a 150 optimax to be a 175?? They are the same engine so i thought there might be some way to get some more hp out of my 150!!!

REW
06-27-2011, 11:38 AM
http://www.bustersmarine.com/Outboards/mercury150opti.html

http://www.bustersmarine.com/Outboards/mercury175opti.html

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So, according to the link from buster marine, the bore and stroke on the optimax 150 and 175 is the same.
That means that both engines use the same block.

So, to answer your question correctly, one would think that if you look in the parts catalog and check the differences between the 150 and 175 hp engines and swap out the 150 parts for the 175 parts, you should have a 175hp engine.

Generally ,when a manufacturer uses the same block to develop different hps, they generally change the induction system, possibly the exhaust system and the engine timing.

So potential things you might have to change would be the intake manifold and associated parts, the exhaust manifold and associated parts, and possible ignition system parts.

Good luck
REW

p.s.
You are right, the 150 optimax can be changed to a 175 optimax with the correct parts changes.

Superfishman186
06-27-2011, 01:44 PM
Strange that the price difference between the 150 and 175 is around $1600-1800 depending on where you look, you would think that there would be a whole lot more difference in the motors. Also the Mercury site does not even list a 2011 175 opti on there site. When I picked my 150 for my boat I asked the dealer why such a huge price difference to upgrade to the 175 and all he said was it was not as popular.

walleyehookups
06-27-2011, 06:53 PM
I upgraded my 135 to a 150 this year based on the computer and did a little flywheel work. I asked the same thing when I wanted to upgrade and I was told that the exhaust timing on the 175 was different and with out replacing the heads it was not possible. Hope this helps.

Neb_ProV
06-28-2011, 05:06 PM
Thank you guys for the comments!! Il probly wont do anything sounds like alot of work for a few mph!!

Legend115
06-28-2011, 09:07 PM
just change the chip!

staylor
06-29-2011, 06:19 AM
Holy 1980s! This is an Opti- not an '86 Chevy. You would need to remap the ECM box- matching the fuel-air-timing curves of the 175. If you could do this- or swap the ECM, then you need to check each sensor on the motor to make sure the 175s and the 150s aren't different. Next you have to pull the powerhead and probably change the exhaust tuner pipe- because Merc likes to change exhaust tuning on the higher hp motors of each block series. While you're at it, pull the powerhead apart and check to make sure the 175 doesn't have bigger or recontoured intake and exhaust ports. Next you go to the reed cages- many times the higher hp motor runs a different reed cage, different reeds, or larger reed stop sttings. Lastly, check the intake shutters and make sure the 175 doesn't have a larger area intake. By the time you're done you will have spent about $4000. at todays rates and parts costs. There are aftermarket firms that will sell you a re-mapped ECM for some engines, but in most cases this will not get you the entire 25 hp difference.
Doug

Legend115
06-29-2011, 10:20 AM
Holy 1980s! This is an Opti- not an '86 Chevy. You would need to remap the ECM box- matching the fuel-air-timing curves of the 175. If you could do this- or swap the ECM, then you need to check each sensor on the motor to make sure the 175s and the 150s aren't different. Next you have to pull the powerhead and probably change the exhaust tuner pipe- because Merc likes to change exhaust tuning on the higher hp motors of each block series. While you're at it, pull the powerhead apart and check to make sure the 175 doesn't have bigger or recontoured intake and exhaust ports. Next you go to the reed cages- many times the higher hp motor runs a different reed cage, different reeds, or larger reed stop sttings. Lastly, check the intake shutters and make sure the 175 doesn't have a larger area intake. By the time you're done you will have spent about $4000. at todays rates and parts costs. There are aftermarket firms that will sell you a re-mapped ECM for some engines, but in most cases this will not get you the entire 25 hp difference.
Doug

welcome to the 21st century. :howdy:

http://www.magnumtuning.com/

Superfishman186
06-29-2011, 08:14 PM
So do YOU have one? I have seen similar products on ebay with ridiculous claims in hp just for swapping a chip..

welcome to the 21st century. :howdy:

http://www.magnumtuning.com/

Legend115
06-29-2011, 09:02 PM
So do YOU have one? I have seen similar products on ebay with ridiculous claims in hp just for swapping a chip..

nope. i'm quite happy with the performance of my engine. :smokin:

walleyehookups
06-29-2011, 09:11 PM
The Magnum chip sends a false intake temp reading to the ECU which richens the fuel air mixture. At best you might get 7-8 HP.

Staylor the ECU is the major difference on the motors but you are 100% correct about the exhaust. Everything else is basically the same. I did ALOT of research on this last winter when I wanted to upgrade my 135 Opti. It is now a 150+

local601
06-30-2011, 08:41 AM
How hard was it to upgrade from the 135 to the 150? I have a 2000 opti and wanted to do this too. Was it worth the cost and make a big enough differance in performance? What did you have to do exactly to do it. Sorry for all the Q's but I'm very interested.

staylor
06-30-2011, 09:46 AM
...is of little benefit to an outboard. This is indeed what was often done on cars years back to fool the computer into adding timing and richening the mixture for minimal added power but often a better 1/4 mile drag or 0-60 times. Early devices of this type were just a simple resistor hidden inside a "high tech" box to provide a simple reduced voltage signal to the ECU from the temperature sensors. Outboard fuel/timing maps for the ECU are factory set at top end rpm to be running somwhat rich and with optimum timing for the available gasoline. Tricking the outboard ECU into providing a richer top end mixture will not help the top speed- since the factory maps normally are rich anyway to avoid frying the powerhead if someone is running a heavy load or too much prop pitch for the rig. For an outboard, you do not want to add timing, or the motor will start to detonate- without the "ping" you typically can hear from an auto engine, with the result usually being holes burned thru the piston tops.

Fooling the ECU to run a rich mixture also hurts fuel economy at cruise speeds, and an Opti normally has exceptional fuel economy at cruise where the ECU is mapped to provide best economy.

Altering the air signal temp will indeed improve the "seat of the pants" feel on holeshot and when transitioning from cruising to top end- because the throttle response will seem a bit quicker due to the richer mixture being provided. But the altered signal does not help the top end.
Doug

walleyehookups
06-30-2011, 09:14 PM
Local, there are a few differences between the two motors the most important is the ratios in the lower units one is a 2.o:1(135) the other is a 1.87:1(150). This can be easily overcome by reproping so your not banging the rev limiter. The easiest part of the change over is removing the restriction from the throtle body there is a rubber reducer that can be trimmed to remove the restriction. The last and most expensive part is swapping the ECU(there are a few for sale on ebay from time to time). Or in my case having it remapped. I also had the flywheel lightened while I was at it. Proformance gains will be boat dependant but my gain was 5+MPH.

One guy you may want to talk fo is Eric Simon at Simon Motorsports. Very knowledgable and customer service was great.

lundeepv
07-05-2011, 10:50 AM
Better look at warranty issues and the legality of doing this. Couple hundred bucks to get 20 more hp??? Sounds to good to be true to me.

walleyehookups
07-05-2011, 06:37 PM
Almost any alterations to an outboard will void your warranty but in my case the warranty was already expired. As it was a 2001. But very good point Pro-V.