1engine several horsepowers?

[George]

One size engine several horsepower ratings? Example Johnson 3cylinder, 50hp, 60hp, 70hp and 75hp. How does the factory do that? What is different? Is it porting, head cc, compression, carburetors? Jets? Timing? I know some year’s hp was taken off prop shafts others off flywheels. Can I take a 50hp and bolt on stock parts to make 75ph?

[Ray Neudecker]

Yes ,there are many basic motors with different horsepowers.Each manufactor has several basic engines in which they build different horsepowers. You have to get real specific before anyone can answer this though,since they do it differently even from one model year to the next.An example are Mercury and Yamaha who use the same basic block for thier 150,175 and 200 horsepower motors.

[jimmyb]

most motors built after the early 80's are rated at the propshaft... remember that the epa has a +/- 10% rated horsepower tolerance for horsepower ratings.

there can be a lot of differences between different horsepower motors that use the same general block, or the difference can be something very minor, like timing and carb jets, it all depends on the specific application...

if you want specifics, you are gonna have to post what you are interested in!

[Looper]

O.k., I'll jump in with a duplicate post. I have a 60 degree 150 Evinrude Intruder (Fastrike). Anyone know how this motor differs from other 150's and how hard would it be to make it a 175? Any improvement if I change the carbs/manifold to the 175 size, but do not change the porting?

Also, I should be bolting it back together in the next couple of days. Any advice for set-up after rebuild?

[tx2step]

Question for Jimmy B.2000 yr Mod,150HpXR6,What does it take to get 200HP?

[George]

Ray & Jimmy
You have similar responses. But can anyone help answer the question? Are the basic/general blocks ported differently or what is it for each hp change? Examples-Johnson & Evinrude in the same year, same cubes& same pistons. 1984&85 2cylinders are rated 40- 60hp / 1995-99 3cyl 50-70hp / 1990-97 4cyl 90-115hp / 6cyl 150-200hp? Merc does the same thing. I have heard the jets & timing thing before and cannot believe it will make that much more hp unless the lower hp motors are very detuned. Same basic/general blocks same year, same cubes& same pistons with up to 50% more hp! Where is the hp comeing from?

[jimmyb]

unfortunately, I have limited knowledge about OMC products, so i really cant help you on any specifics:

merc v-6's:
the main difference between the 150-200 models is the porting (liners), carbs, or EFI programming. Please note that the differences that I am listing below are the general differences between horsepower ranges. There are always exceptions and mercury varied its motor design from year to year to year...

PORTING:
150 models: have low exhaust ports as well as lower boost and transfers. Also there is an "idle relief" slot cut on the exhaust port. In order to properly get a 150 to be like a 200, you should put in 200 liners. This is quite costly. You can grind away on the 150 liners, but you will always have the "idle relief" cut that will bleed power.

175: no idle relief cut, and you should be able to grind it like a 200 with out too much of a problem. I believe the exhaust port is lower than a 200, but some 175 models did use the same block/liners as the 200. it depends on your year.


CARBS:
150/175: the butterflys were a smaller diameter.
200: larger diameter butterflys.

EFI:
each ecu is calibrated for the specific motor HP. You should try to run a lower HP ECU on higher HP engine because you will run lean...

FINAL WORDS: Always buy the most horsepower you can! The cost of upgrading is usually quite expensive and usually not worth the effort. You are usually better off selling your existing motor and buying a higher horsepower one.

[Ray Neudecker]

i also am not familiar with the specific motors you are asking about.Many times you can take the parts manual and figure out what they are doing.Yamaha for example using different reed blocks to reduce the 175 to a 150. if you change the reeds and carbs in some models they go from 150 to 200. there is one model, you change the intake manifold for 25 hp.There is one model a timing change will give you a 25 hp increase. the only difference in some models are the carbs.You need to talk to a long time servicer on whatever you are planning to work with. Tuners have also been one of the ways of decreasing hosepower. most of the people have studied the bigger engines much more than the smaller ones as far as horsepower gains. This is where the time has been spent on large increases. the best info on the smaller motors will come from people racing in the small engine classes such as Sport C and the 50 and 70 horse classes.

[Gerben]

Hi Ray,
I'm picking up a 175 '88 Yammie this weekend. Is this among the beforementioned motors with an easy hp increase?
(and would you happen to have partnumbers if so)

Thanks,
Gerben

[Ray Neudecker]

if you change the carbs to the 84 model v6 special or 220. it will produce 210 horsepower at the prop.

[Ray Neudecker]

the only differencein the Fast strike 150 and 175 were the port heights and widths in the exasth ports. newer models which were more strictly looked at had carb differences also.

[Ray Neudecker]

Mostof the 150 hp Mercurys showe a very noticable horsepower increase by changing the tuner to the old model 200 tuner regardless of year model or whether or not EFI. This has always been a mst hp increase for the dollar on them.

[George]

Ray & Jimmy
Thank you for the information! It will help me and some others in our search for more horses. Yeehaw!

[Gerben]

Many thanks Ray. I agree with George: Yeehaw......

Gerben.