View Full Version : need training for a 20 hp merc

03-25-2003, 11:52 AM
hello everyone, i'm trying to locate some info on the net on how to tune a small 20 hp mercury for performance, but its like no one on the net care about those little rigs...
i know its very small & maybe nobody care about those, but since i'm a kid i dream about performance with a small engine (maybe just to kick ass of bigger boats, & i'm still looking to do that...
i've been able to gain 8 mph with my family boat just having the right propeller & a little carb tune, so i guess it could be done with the small one..

i had a talk with a merc engineer last week & he give me some clues about prop tuning, higher pitch & hole on the side(like on my high five on my boat) to reproduce the effect of the shopper, but its like nobody have ever done it, your maybe its just a too small engine to talk about.

my engine is a 95, the engine is plain stock right now & i'm able of 32 mph on a calm lake without wave.
my goal at the end of the summer would be 40 mph.
i assume that with a good tuning, i should be able to gain some good mph...

please help me if anyone have a good idea

(,sorry, i've realyse my post was not at the good place...)

03-25-2003, 02:50 PM
Props and engine height are all you can do with these motors. There was a message on outboard tech in hot boat last month. No perf parts for the 20 Mercs. It would be cheaper and more reliable to just go up in hp. I'm running three 9' Virages. One with a '95 15 Merc and two W/ '85 25 Mercs.
Good luck and welcome aboard!!!!

10.5' Tunnel
03-25-2003, 04:00 PM
What do your Virage's do with the 25's?

03-25-2003, 06:58 PM
we all got to start some where, boating is a lot of fun...Merc use to make a chopper prop it was 18 ptich..ssteal three blade.mybe you can find it used so it wont cost so much, it was in last years merc master assocories catalog...its been around for quite a few years and with it you can jack up your eng to where the water intake is just below the bottom of the boat or you can get a mini-jacker from the bass pro marine catalog page 64 for about 59.99 ...at least its a start..:) :) :)

03-25-2003, 07:24 PM
I'm getting 35 mph with a stock prop. As the kids get older, I'll upgrade them to 35 or 40 hp motors with trim. Here's one with a 25.

10.5' Tunnel
03-25-2003, 07:24 PM
I had a 20 on my tunnel, that had NGK spark plug wires, and spark plugs. I swear that boosted me up a few mph. It is a late 70's merc though, so i dont know if it is possible to do it with a 95. You may not want to risk it either :eek:

BTW, nice lookin boat Alaskan, lucky kids :)

03-26-2003, 09:38 AM
thanks a lot guys,
right know, its on a 14 foots regular fiberglass(i dont know the word in english:launch, utility, fishing, poor man's boat...)
(sorry for the french to english translation...)
the engine have right now the regular height , prop is the stock 13 pitch.

sure its not a sport boat or a tunnel made for speed but its a good way to learn tuning technique on a very small budget...
plus, you could imagine the face of guys with 70 or 90 hp, being pass by a 20....(hahaha)

i dont want to go bigger hp, cause my oldest girl just turned six years old & in a near future, she will get that motor( i'm building with her right now a wooden "ski boat" vintage look & try to get some performance too, & this engine will be on her rig...

thanks about the info on the height, i will try this,
did anyone have the parts number for the chopper, my merc dealer just can't locate it.

03-26-2003, 08:13 PM
I here ya jimmo, ive got a 12ft aluminum flatbottom with a 40 merc, ive had all kinds of motor work done including stuffing some 2.5 pistons in it. Currently it runs about 72 (radar) i love blowin by bass boats and some "performance" boats, you should see the looks on their faces. :p

10.5' Tunnel
03-26-2003, 08:20 PM
WOW!!!! 72? You got any pics of the rig :eek:

03-26-2003, 08:35 PM
im tryin prolly have some pics of it tommorow:)

03-27-2003, 02:00 AM
F%$k yea I wanna see some pics!Now were talkin'!:eek:

03-27-2003, 09:28 AM
72 mph, this is impressive,

so i guess you understand my thingking, blowing bigger rigs...ha

hey guys, sorry for ignorance, but why taking the engine back will increase my speed?

about the prop, did anyone know something about making holes on the side, like on lazer II or high five??
about the pitch, is there a home made trick to crop it??

03-27-2003, 12:52 PM
if yall think 72 is impressive you should see some of the other guys rigs i know. I regularly get my ass smoked by these other two one is 10ft and the other is 12ft, they both run around 75. All of our boats are still tiller steering too. youll see what i mean when i get the pics up.:eek:

03-28-2003, 11:04 AM
hey guys, iv'e just tryed to order a mini jacker, but they are not available right now( non stock)

i can't wait to try it thought.

thanks for the input.

did anyone have any idea about hole in the side of the propeller?

03-28-2003, 08:34 PM
behind the leading edge of each blade,to allow exhaust gases to escape around the prop. This causes a desirable prop slip until the engine can reach it's powerband and theoretically turn a bigger pitch prop.