25 mercury horsepower upgrade

dawson29

dawson29

Well-Known Member
I just recently took off the carburator restrictor plate and installed one from a 30 hp motor. Ive heard this is the only difference. Has anybody had experience with this. By opening up the fuel passage ways does this make wearing faster? Typically how much hp can you actually add.
 
Going from 25-30 hp is a 20% increase in power, that's significant. One thing they did mention was it's uses more fuel but then again horses need to be fed. :LOL:
 
never knew you could do that. can you tell me where you got the restrictor plate, did you need anything else and how long it took you
 
mightyhunter1 said:
never knew you could do that. can you tell me where you got the restrictor plate, did you need anything else and how long it took you
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A 15 HP kicker is nothing more than the 9.9 with a carb change. Same as the upgrade from 250HP Merc to 300HP. Same everything except fuel delivery. More carbon more power.

What year, make model engine do you want to upgrade? That info is needed.
 
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Seems to me that this is pointless to do to your little engine.
Curious how many km/hr does this add to your top speed?
 
G.Mech said:
It is already stated above that the gain is 7mph on a similar boat....so for the price of a gasket, why is it pointless?
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Okay I missed that one post MY BAD
Was just thinking if top speed was important to someone
Why would that someone buy a boat with a 25HP motor...
Guess I'm just old school that way.
 
Derkd9 said:
Okay I missed that one post MY BAD
Was just thinking if top speed was important to someone
Why would that someone buy a boat with a 25HP motor...
Guess I'm just old school that way.
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Your much too young to be old school young man.:p I'm old school... I can remember when a 25 horse outboard was the bad boy on the lake it was so fast.:jawdrop: To get an extra 5 hp was like stepping into the power boat racing category.:woot: :D:D:D
 
Wave Runner said:
Your much too young to be old school young man.:p I'm old school... I can remember when a 25 horse outboard was the bad boy on the lake it was so fast.:jawdrop: To get an extra 5 hp was like stepping into the power boat racing category.:woot: :D:D:D
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Lol okay fair enough
It was more of a figure of speech
Being a smart ass I guess is a good way to describe it
If I wanted a fast boat with lots of HP
It wouldn't be a small boat with a small outboard engine attached to it.

Respect
 
allot of old 14-15' tinnys are rated to a max of 20-25 hp so if you can gain an extra 7 mph ...it is a huge bonus

plus like me sometimes you have too make the best of what you have , It would be nice if i had abigger boat but my 14' with 20hp is perfect for my annual cochrane fishing trips
 
Digging up an old thread.....just picked up a 25hp 'Merhatsu' seapro and am looking for the part # for the 30hp carb gasket.....appreciate any help!

Josh
 
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Thanks! Not 100% sure that's it but I'll tear it down tomorrow....need an impeller as well. Seems to be limited info on these motors for some reason!? Gonna have to cross reference the serial # and see what I can find.

Josh
 
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@Josh Roelofsen… After some more searching apparently this is the upgrade gasket Tohatsu #346-0211-1 to upgrade from 25-30 hp. This link thoroughly explains what is a fairly simple procedure to make the upgrade. It says for Mariner but it's the same procedure for the Sea Pro. I believe it says the timing needs to be advanced 5 degrees after installing to get the full benefit. Other articles said the only difference between the 25 and 30 hp is this gasket and the advanced timing which gives it 250 rpm more that gives as much as 7 mph increased speed. But they do say it comes with a cost of less mpg in fuel economy. These are available on Amazon and Ebay and hopefully your search is over.

1529849485779.png 346-02011-1.jpg
 
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