I recently put a mercury optimax 200hp on my boat I did it all by myself and am very surprised that it’s not any faster than the 150hp Blackmax that was on it I’m wondering if anyone has ever upgraded power and not got a boost in speed the new motor is a 2002 rebuilt in 2008 with 110 compression the old was a 1988 with 105 compression before it blew I put the same prop on the new motor a high five not sure the pitch also I should say that I’m not sure what rpms I’m running as I don’t know how to hook up the tachometer plus I don’t think it works at least never since I’ve owned the boat  anyway thanks for any help or response 

You need a a tach . More horsepower will not  give you more speed, if the same prop is turning at the same rpm at wot. You should however  have a much better hole shot.

To take advantage of the extra horsepower you need to get a prop with a higher pitch. A tachometer is about the only way to know if you are running the best prop without running too high on the rpms. Running a prop with the pitch too low, without knowing how fast your motor is going, is a good way to blow another engine.

Okay thanks I’m planning on getting a new tachometer put in or getting this one hooked up and having them double check everything it’s just every shop in the area is booked till mid to late august 

First, you have to realize, the numbers on an engine does not mean that's the actual hp of that engine.  That's the average within 5-10% of that production model.  Then you have to consider the condition and state of tune of the motor.  That's just like you can take two identical new cars and one will blows the doors off the other.

You say the 200 was rebuilt, if bored, especially .030" or more, that can cause a significant drop in performance.  The ports in most modern two stroke engines are angled upward, so boring them drops the port height, which drops the power band and rpm of the engine, and trust me, no average rebuilder is going to spend the hours it takes with a die grinder to grind them back to specks.

Then you have some production models that are intentionally built with more hp than the numbers on it say to out perform a competitor's motor.  A good example was the 92 Johnson 150 FastStrike.  They built it with almost 200hp until Mercury complained about it running with their 200's, so they were forced to  reduce it back to specs.  Others were built specifically for boat manufactures to make certain models run better than the coastguard rating would let them.

So, numbers on the decals mean very little as to how the motor actually performs.  Shoot, I can show you some motors the decal an serial number says they are 200hp, the dino says they are well over 300hp.

 

12 hours ago, Way2slow said:

A good example was the 92 Johnson 150 FastStrike.

 

Evinrude/Johnson did a lot of that kind of stuff.