# Mercury 25 hp 2 stroke "High Performance" Engine?



## jimbarn1961

I was looking at doing that to a while back.  Local marina said involves carboration, reed valves for increased gas air in to make power.  then larger exahaust to get rid of it on the other side.  Was told why molest the motor it would usually be more cost effective to sell said HP outboard and upgrade to similer year higher HP outboard. then to buy the parts and labor to make more HP.  Just my .02. 

Ulterior motive more HP but still legal hp rating for hull or particular area fished??? ;D


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## Flyline

it's had been done but it's not worth it because of too much money involved, decrease engine life down to 50%, and speed aint much difference.... leave it alone and start looking for 30-50 hp 2-stroke...


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## Yoreese

I agree not worth reliability issues.


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## mark_gardner

sell it and buy a bigger motor for the reasons stated above


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## DuckNut

Let me pose this...there is an entire class of APBA devoted to small engines and those things fly. I am quite sure they are not using the off the rack motor.

I have looked but I come up empty on these special motors but for the larger engines they are coded XS.


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## Brett

From my boat porn collection...


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## Brett

and another...


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## Brett

and a mini merc


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## richg99

I am FAR from any kind of mechanic...so take this with a grain of salt...please.

What is the real problem? 

#1 Are you having problems getting up on plane?

#2 Are you trying to carry a heavier load of gear or fishermen than the rating?

#3 Do you feel you need more speed?

If it is any of these issues, either adding 
Smart Tabs ( problem #1);
or changing out your prop might help on #2 or #3. Adding a jack plate and repositioning your engine height can help a lot, too.

More power solves some problems that could have been solved with simpler measures.

FYI....I had a 14 ft Carolina Skiff some ten years or so ago. It was sluggish out of the hole. I went to my local boat guy and I wanted to buy his 35 hp motor ( more h.p. than the boat was rated for). I wanted to trade in my 25 hp. 

Instead, he sold me a $55.00 Doel fin. The Doel Fin solved the problem and I was a very happy guy. 

I bought a number of other motors from him ( an honest man! ) over the years.... for different boats, too.

Rich


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## gheenoe

The mercury XS motor use standard powerheads. The big difference is in the mid section being super short and a different lower unit with a higher gear ratio.


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## Guest

Thanks for all the input! I'm looking to buy a Mercury 25hp 2 stroke and just wanted to confirm what I thought. I've read that adding the Reeds don't produce for the money and a stock motor will suit this skiff fine. 

I'm also looking that those Mercury 30hp 2 stroke, but only come in a LONG STROKE! I would have to modify since the skiff has a 15" transom. I would say that 5hp is not going to make much of a difference when 90% of the time I fish Mosquito Lagoon vs. the modifications I would have to make.


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## Yoreese

> Thanks for all the input! I'm looking to buy a Mercury 25hp 2 stroke and just wanted to confirm what I thought. I've read that adding the Reeds don't produce for the money and a stock motor will suit this skiff fine.
> 
> I'm also looking that those Mercury 30hp 2 stroke, but only come in a LONG STROKE! I would have to modify since the skiff has a 15" transom. I would say that 5hp is not going to make much of a difference when 90% of the time I fish Mosquito Lagoon vs. the modifications I would have to make.


I have been told that the 25hp was actually under rated by Mercury.


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## cutrunner

lol brett knows what time it is! if your serious about modding your 25 hp merc go to www.screamandfly.com there are some guys on there that are hardcore experts in outboard racing. im a member


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## Guest

> I am FAR from any kind of mechanic...so take this with a grain of salt...please.
> 
> What is the real problem?
> 
> #1 Are you having problems getting up on plane?
> 
> #2 Are you trying to carry a heavier load of gear or fishermen than the rating?
> 
> #3 Do you feel you need more speed?
> 
> If it is any of these issues, either adding
> Smart Tabs ( problem #1);
> or changing out your prop might help on #2 or #3.   Adding a jack plate and repositioning your engine height can help a lot, too.
> 
> More power solves some problems that could have been solved with simpler measures.
> 
> FYI....I had a 14 ft Carolina Skiff some ten years or so ago. It was sluggish out of the hole. I went to my local boat guy and I wanted to buy his 35 hp motor ( more h.p. than the boat was rated for). I wanted to  trade in my 25 hp.
> 
> Instead, he sold me a $55.00 Doel fin.   The Doel Fin solved the problem and I was a very happy guy.
> 
> I bought a number of other motors from him ( an honest man! ) over the years.... for different boats, too.
> 
> Rich



Thanks, but none of that "stuff" is what I need. 

I know you can do all kinds of things to these motors to increase HP, but know that boring out heads etc.......is not going to be worth it vs. cost. Maybe just forcing air to the motor or just squirt a little NOS! 

I'll read that race forum(sreamandfly) and see what "cheap" things can be done to increase power.


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## cutrunner

the biggest speed gains will be with your lower unit gearing and proping the boat right.if you do anything at all get the right proppellor


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