Which of these 25hp motors would you keep and why?

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thecadman99

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I've went a bit crazy and bought two boats....

One has a 95 Mercury electric start (long shaft)- I just put an impeller and seals in the cooling system. It runs great but vibrates a bit at idle (I'm told this is normal) and pushes the boat to 20mph with a 9 pitch prop.
The mercury looks really clean inside and "seems" to have low hours (no dings, prop looks good)

The second boat has a 92 Johnson electric start that is a bit oily and dirty inside. The PO says he's only changed the lower unit oil every winter for the 3 years he's owned. He says its always started and ran well since he has had it. I found about a tablespoon of gas in the bottom cover, right in front of the carb, with a drop of gas hanging off of the float bowl.
The prop is a little more beat up on this boat.

The Johnson cold started almost instantly on muffs and idled smooth. I have not tried it on the water yet, but will this week.

I'm only keeping one boat and one motor. I'll be keeping the 92 sea nymph boat, but I'm wondering if the Mercury would be a better choice than the Johnson? Educate me please!

Assuming both have good compression (have to borrow a gauge). Which of these motors would you prefer to have on the back of your boat and why?

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seanymph.jpg

johnson.jpg
 
I say the Mercury... But mercury is a I've ever own and all I ever will own...

I'm not gonna knock them omc 20/25/30 though.. They are pretty much bullet proof.. The 25 mercs do have some flaws, but I'll stay with them... I've had 5 in my life and I own 2 now...

As far as the why? I'm a merc man...haha...

Or, keep the omc and sell me the merc for $200!!
 
I'm generally an OMC guy, but these two are toss-ups. The only way I could pick one over the other is to look closely, listen closely, and spend a few minutes on the lake with each one. Then I could make a pretty good guess at the better one.
 
I'd probably start with a compression test and see what I had in each motor. Also check the lower units for leaks.

I've owned both Merc and OMC 25hp motors and prefer the OMC overall. The Mercury was a bit cold hearted in the winter, and mine also idled rough, enough to be annoying. The OMC motors are cheaper to work on, plus all of mine have always started easier than any of my comparable Mercs.
 
Mercs of that vintage are more prone to two issues.
One is the ignition system. When it goes it is also more expensive to repair than the Johnson will be.
Second one is gearcases. Somewhere around that vintage Merc had some manufacturing issues with the gearcases in that family of engines.
Not sure of the exact year or years on the second issue so take that one with a grain of salt so to speak. Know it was around that year though.
 
Wow, thanks for the useful info :LOL2:

I hope to get a compression test done on both engines by tomorrow, and get the johnson out on the lake as soon as I get the title transferred (the DMV just ain't made for working folks).

I do have a couple more questions.
Will these motors weigh about the same? (the Merc is a long shaft)

I've heard that the 25 johnson can be upgraded with a 35hp carb, does anyone know if that is true?

Thanks again
 
Pappy said:
Search is your friend. The 25hp can be upgraded fairly easily.
I've read all the posts about upgrading, but I'm still unsure about what I need besides a carb. Some posts suggest you need an intake, while others don't. I guess it depends on the year.
 
The Merc is lighter, by 15+ lbs. The OMC's block has more cubic inches, and can have the carb upgraded.

I've had both and they were both great engines, free of major issues. It really sounds like you'll end up with a good one regardless of which you choose.
 
Both are good motors IMO. I'd just keep the Johnson... because it's already mounted on the boat! I run the same motor and it's been reliable and easy to work on... hauls *** too. If you want to make it a 30 HP all you've got to do is some carb work. In like the late 80s they started rating horsepower at the prop instead of the crank, so the older generation 35HP motors should be the same as the newer 30HP motors.
 
im an OMC guy but don't know much about the 90's and up small johnny/rudes.. that being said I would take the Johnson just because I know they were(pre 90) built bulletproof and reliable
 
Well, after taking the new(er) boat out for the first time today, I'm keeping the Johnson.
I'll be selling the older boat with the Mercury on it.
The mercury looks so much newer, but I really liked the ease of cold starting the Johnson, and it seemed smoother at idle. I don't have the same props so I can't compare power, but the Johnson, with my wife and I in the 15.5' boat, and your average fishing gear were running 24 GPS mph at 5200 on the "rough" 10X13 prop.

I did find a small leak from a small fuel like that runs down the right hand side of the carb (looking aft) that I'll have to take care of. It seemed to cause the boat to miss at idle, every time it missed a small mist of fuel would come out of the hole in the line.

The Mercury in the lighter boat ran 20mph but it only has a 10-3/8X9 prop (it really came out of the water quick).

I've already ordered a carb to tinker with on the Johnson https://www.ebay.com/itm/301331097931?_trksid=p2059210.m2749.l2649&ssPageName=STRK:MEBIDX:IT

I'll probably get a new prop after I get the carb figured out.
Thanks for the replies all- I'm lucky to have two nice motors to choose from. Now to sell the second boat! You guys think $1500 is a decent price for the brown boat in the pics?
 
not sure on a 92 but you may need more than just the carb.. also you might want to check your manifold and leaf assembley against the 35's...
 
I can't pick one, but personally I have had a 25 Johnson that I bought new in '97. Never gave a bit of problem (that I couldn't fix)and I have beat the crap out of it. Think "hitting a river ledge at 25 m.p.h.". As for the OMC prop, only $65-$70 bucks.
 
Boat2fast said:
Did you say one was a long shaft? Careful not to mix long with short, transoms and motors.
Yep, they are both long shaft motors. The brown boat has a 15" transom so it really needs a jack plate (I have the parts to make one) but the grey boat is made for the LS.
 
Well ,leave it to me to monkey wrench in here...... seeing as how you brought both boats... I'd swap motors and controls , take the best electronics and features and put them all on the brown boat with the mod-v. and sell the flat bottom. :mrgreen: :mrgreen: :mrgreen:
 
Charger25 said:
Well ,leave it to me to monkey wrench in here...... seeing as how you brought both boats... I'd swap motors and controls , take the best electronics and features and put them all on the brown boat with the mod-v. and sell the flat bottom. :mrgreen: :mrgreen: :mrgreen:
Lol, I pretty much did the opposite. The newer, less hours motor on the brown boat, and that's the one I'm selling.

The wife likes the casting decks on the flat bottom so if it means keeping the better half happy, I'll have to keep the newer boat.

I did manage to get my 35hp carb in, and though it is a little different I got it mounted up and running. I've only ran it on muffs so far.

I started a new thread in case someone else wants to see the results of changing carbs.
 

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