Mercury 25

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elrodphil

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Hey Guys, I read a lot about people wanting more out of their outboards and I completely "get it". We'd all love to go 65MPH with a 9.9...ha ha...fast is not fast enough when you're ready to get home...

I have a 2002 mercury 2 stroke 25 short shaft tiller on a Weldbilt 1549...so far it has been a really good fishing boat. My question is...

How can I get my engine to run as smooth as possible and what type stainless prop do you recommend? I want good top end speed and I don't really have to have blazing hole shot. I want it to idle as smooth as a 2 stroke can and just perform generally good. If the cavitation plate is a little below the transom should I move it up to be level?

Any suggestions?
 
A SS prop on that small gear case is not the best idea. One it probably won't gain you much if anything, two the $ you spend, and 3 it's a lot less expensive to fix an aluminum prop than replacing gears and what not if you hit a rock with the SS prop.

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Thank you! I think I might just get a new aluminum prop...maybe just a stock mercury aluminum. It has the stock prop now but it is kind of beat up....
 
I know a couple of guys running ss props on that size motor. Fishing mostly deep ,clear,open water lakes. But when they go to the rivers they put there spare spitfire props on. I'll have to ask but pretty sure they are quick silver, Silverados


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For better hole shot you could look in to a hydrofoil. I had a SE200 on my 1992 25hp Evinrude. It really helped get up and also at slower speeds it helps stay on plane.

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One runs the Silverado the other runs Vengeance there the same prop but the Silverado doesn't have the name stamped in it and less money


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Unless your current prop is dimensionally inappropriate, imbalanced, or damaged, I don't think a stainless steel replacement will make much difference.

With 2-strokes I've had, I noticed that performance would decline when crank bearings became worn, regardless of good compression. Vibration robs power, they rev slowly and won't reach max RPM in some cases. Same with connecting rod bearings.

If price were no object, I suppose you could put in new crank bearings and seals, connecting rods, pistons and rings. Mill the head a tad to increase compression, etc.

But it's probably cheaper to just get an engine with a bigger number on the cowling.

Also, high performance costs reliability.

Maybe just go cheap. Put in new spark plugs. Empty the whole boat and only put the necessities back inside. Then wipe the whole boat and motor down with lemon Pledge so it gleams and smells fast. ;-)
 
If you want a fast shortcut then throw on the highest pitch Merc brand prop they make. That will probably do it. To do it right then you need a tiny tac and prop it to max recomended RPM. Call Ron Hill propellers but you need a tachometer first. He invented fast props and can help if you call and ask. IMHO if your engine is so low that it never cavitated then it's too low. Raise it to the point that it cavitates only on high speed aggressive turns. Drop it until it does not do it much or bother you. That's usually the right height. To get better idle then fool with oil ratio. 30:1 all the way to 50:1. Measure perfectly every time. Milling the heads as said is easy and works great and if you want to piss off Pappy then call Criss Carson for a set of reeds. Send him the whole reed block if he request it. If not fresh stock reeds usually freshen up poor idle and performance. Best bet is to ditch the time bomb merc. I just sold one this morning. Thank goodness that POS is off of my property. Yours should fetch good money. My 1991 8hp electric start long shaft brought $550. Fool and his money... Trade for that new lite weight Yamaha 25 if you can swing it and never look back. If not call Chris Carson. He might mill your head as part of a reed deal. Mercs start well and run fast. Ever other aspect of them sucks. https://www.chriscarsonmarine.com/reed-valves.htm
https://www.chriscarsonmarine.com/reed-valves.htm
Fixed link
 
Yeah ditch the p.o.s. Merc or better yet trade it for an O.M.C plus cash and put the money towards you and your sisters wedding or banjo lessons.I will agree with stumpalump despite him being a suspected Johnson lover.Start with propping,motor height,trim and weight distribution.Some shops will let you try props before buying.As mentioned use a tach. You should see 30mph with your rig.You can also advance the w.o.t timing but not sure if this is recommended with a mercosil block.Also your motor does not have a head and requires a larger piston to increase the compression ratio.Do some research on this engine and you find if properly cared for these motors will last a long time.The jury is still out on the new Yamaha. m.w.
 

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