20 merc vs 25 merc

skiffer

Seaman
Joined
Apr 23, 2003
Messages
68
I am considering buying either a 20 or 25 merc 2 stroke new. Apparently, they both are identical except for hp. I have heard they put smaller ports in the 20 to reduce hp. I don't need 25 on my boat and would save the extra expense and get the 20 if everything else was equal. My questions are: is there any difference between these motors in ease of starting, especially in cold weather, longevity of the engine, etc? Thanks.
 

graddy

Petty Officer 2nd Class
Joined
Apr 3, 2003
Messages
150
Re: 20 merc vs 25 merc

Main jets in carbs and porting in the cylinders are the difference between the two. The 25HP RPM range is 5000-6000 20HP RPM range is 4500-5500. The weight is the same. You would only notice a few MPH faster at top end with the 25HP.
 

skiffer

Seaman
Joined
Apr 23, 2003
Messages
68
Re: 20 merc vs 25 merc

I called Mercury this am and spoke with a technical guy about this. I was especially concerned about any differences in cold weather starting since I hunt sea ducks in the winter here in New England and am not especially interested in getting stuck out in the middle of the bay some January with a cold front moving in and a motor that won't start. <br /><br />He told me the only internal differences between the two motors are in the carburation and the exhaust, which is tuned differently. Both power heads use Yamaha parts. Both use loop flow induction. He says both will start equally well in cold weather. Only difference seen by the user is 5hp. <br /><br />For really severe cold conditions Mercury sells a "cold weather" kit which preheats the fuel-air mix, which he says is only necessary in really cold climates, I assume Arctic.<br /><br />Surprisingly enough, this guy was also a duck hunter and had the same size boat as mine, 16'. He bought the 20hp for his, because it was cheaper, but now wishes he had spent the extra $$ on the 25, simply to have that extra 5hp when needed. He winter hunts in WI and says he never needed the cold climate kit.<br /><br />I was truly surprised and pleased to be put in contact with a knowledgable person when I called Mercury. Usually when you call a big company like this you get nowhere trying to get technical information. I'm an old Johnson addict but am now starting to get a warm and toasty feeling toward Mercury.
 

skiffer

Seaman
Joined
Apr 23, 2003
Messages
68
Re: 20 merc vs 25 merc

I would like to correct a statement in my post above - there I no Yamaha parts in 2 stroke Mercury engines. Sorry if this caused any confusion.
 

FlyBoyMark

Ensign
Joined
Apr 14, 2002
Messages
934
Re: 20 merc vs 25 merc

Carb only...exhaust tube is a VERY late model addition And makes little difference in performance. They both would have the same hole shot performance. 25 HP would be about 3 MPH faster than the 20 HP on a 800 lb load
 
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