25 yamaha

[25yamaha]

I have a 1992 25hp Yamaha with electric start 2 cylinder that I will run on a 14' StarCraft sf14 deep v boat, I usally only fish with another guy 160 me 185 along with 250lbs of gear
now I have some questions about it..
1.) is this motor a "big" 25 for its class
2 if its not a big 25 how much time to plane, and top end will I loose if I go to a 20hp 4 stroke, what about a 15hp 4 stroke
3 will a hydrofoil plate decrease my top end speed at all? if so how much? what are some other disavantges I would have with this?
4 what size prop should I get to fit my current set up better it has the stock on it now and is chipped pretty bad
5 how more top end will I get if I get a new ss prop? what about aluminum?
6 what other fairly inexpensive options can I do to get more power out of my set up?
7 is this the same block as the 30hp if so how do I upgrade to the 30hp
8 what kind of speed should I expect out of my set up

thanks everyone in advanced I have not run this motor on my new boat and have a lot of questions about this motor
thanks again

 

[Mike Redmond]

Unless the exchange rate for US vers CAN money is exceedingly high,it wont be worth it.Outboard motors out here sell for close to twice the price compared to south of the border,,,just my two cents

 

[turbotodd]

Depends on which 25 it is.....There are no less than FIVE 25hp yamaha's, all 5 different.

Aside from two different 4 strokes there is a 25 and a C25. And a 3 cylinder 25. Regular 25 is usually model designated 25ESH, 25ELH, 25MSH, 25MLH, 25MH, etc. Those have two carburetors. 395cc engine which is the smallest displacement of any of the 25's. Great motor! They idle better (much better) than the C25.....

The C25 is nearly 500cc engine size, so that is your "big block" 25. Single carburetor. C means Commercial or Cheap, or as one of my techs says "crappy". It was a "cheaper" 25hp motor to compete with the Evinrudes and Johnsons and some of the Merc/Mariners. At one time I sold both Yamaha and Merc/Mariner. Hands down the Yamaha was/is a better motor, other than the Merc/Mariner shift-in-the-tiller which a lot of duck hunters love. I personally hate it but that's just me. Anyway the C25 is the same as a C30 aside from the carb, inner exhaust cover, and maybe other differences as well, that I'm not fully aware of. Have a look at the parts diagrams and compare the numbers. Looks to me like it'd be easy to make a 25 into a 30. But there's not enough of a speed difference to justify it, IMO. Maybe 2 mph?

Also IMO, the idle quality and resale value of the twin-carb 25's are a LOT better than the commercial 25's. And even those pale in comparison to the 4 strokes, which then pale in comparison to the triple 25 (see below). That being based on my personal experience. Yeah you might go a little faster than the 4 stroke but when it comes time to sell it, you re-think that speed.

Then there is a FIFTH 25. A 3 cylinder. Made 3 years I think. 96, 97, 98. There might have been some 99's as well, I'm not on the "up and up" with the triple 25's. Those are the ones that can be modded...I know of at least one that made 80 hp. But kiss reliability goodbye!! Race motor only. If you have a triple, keep it. Or sell it to a duck hunter for about $3,000. Then use the money to go buy 2 4 stroke motors and sell one of them for a good profit and keep the better of the 2. I like 2 stroke motors, don't get me wrong, but as more and more of the 2 strokes find their way to the scrap iron yards, the 4 strokes are slowly getting more popular. As I said, I like the 2 stroke motors but I like the 4 stroke motors a LOT better. Never thought I'd own one, now I don't know if I'd want to go back to a "smoker".

The F15 and F20 became the same motor in about 2008. There were minor differences...carb I think. Neither one of them is a powerhouse, per say. They're 15 and 20hp, respectively. I've had both. I currently have an F25 (2000 model). Ran an F15 on the same 1548 boat briefly, and honestly it wasn't that much slower than my F25. But where you really noticed it was getting on plane. Somewhere on this site is a video showing the differences. Time to plane was about 4 seconds difference. Top speed with the F15 was 23.1 mph. Top speed with the F25 is average 29.5. I like both, but kept the 25 and sold the 15. The 20 is a middle ground motor between the two, and WAY lighter than the 2008-newer F25's. Same weight as the F15, as it is the same motor more or less. On my boat, if I had run a little heavy like we normally do when the GF decides she wants to go (we take everything...cooler with food, drinks, her iPad, charger, extra battery to run her stuff, etc), then I don't even think the 15 would plane the boat.

Hydrofoil CAN decrease your top end speed if the rig is not set up right. Meaning the foil needs to be out of the water totally if the boat is on plane. Honestly, on the little motors (90hp and smaller) a hydrofoil isn't really worth the money unless the rig has some other problem-like my old boat did.

What size prop? Don't know which motor you have. twin carb motors do well with the factory 9 7/8" by 11 1/4" aluminum prop. Good for upper 20's with the right hull. Don't know on the C25...probably pretty close with an 11" pitch there as well. Maybe even a 12" since I think the max RPM is only 5500 on those compared to the twin carb's max RPM of 6000. SS, yeah you'll go a little faster...maybe 1 mph at the most. I like the Turbo hotshot on the 25's and that is also what I run on my 4 stroker.

If you have a C25, and knowing that the C25 and C30 are basically the same motor, I still wouldn't put a dime into it since it's not worth a lot of money to begin with. Unless you have money to burn. As I said, watch the parts diagrams closely and you'll see where the differences are. Might also have to make an ignition timing adjustment.

 

[Johnny]

Geeezzeeeee - - - all those questions make my head hurt !!!
Boating is supposed FUN !!!

 

[25yamaha]

Thank you to every one who contributed my model number is c25elqr or something like that

 

[muddywaders]

Before you buy a new motor you should consider what conditions/waters you will be using your boat in.If you fish the ocean or rivers with strong currents and waves I recommend at least 25 hp preferably 2-stroke.Power can get you out of trouble in some situations.I own both versions of Yamahas 2cyl 2-stroke 25hp motor.Currently running the 25msh on a 14' Lund and although its very smooth and trolls down great I prefer the C25.When pushing through waves the 25esh the boat will slow and rpms will drop requiring more throttle to maintain speed where the bigger motor keeps chugging along and using less fuel although it displaces 100cc more.Dont think the commercial model is "cheap" but simple and rugged and only weighs around 100lbs.Yamaha's 3cyl 25/30 two stroke is a beast-my friend had this motor on a 14' Mirrocraft and it jump up on plane instantly with 5 people in the boat and go almost as fast as it would without a load.I highly doubt even the latest four-stroke 30 can compare.Suzuki?Until Yamaha can build a lighter torqueir F25 that retains manual start I will never hang one on my 14'er.If I ever buy a new 25/30 hp outboard(win the lottery)I may go Suzuki.Any reviews? tight lines M.W.

 

[DaleH]

#3 FOILs – While you can potentially lose 1-2 or tad more MPH off the top end, you can realize some key or important performance benefits. Not only that … WHO runs around with small skiffs @ WOT all the time anyway? I sure don’t. As a rule, I run my small OBs at ~80% throttle most of the time, with occasional bursts of high power speeds. All of my OBs run like a top and just keep on running! I think the most my bros and I have run in a year is 13 or 14 motors, plus I take care of another dozen or less at my boatyard.

Here’s what I believe are the benefits of a foil, when set-up right, that is:

1) Eliminates bow rise when planning out, which can be critical on smaller skiffs
2) Makes the boat much more stable and safer, plus tracks better in corners and whilst crossing waves/wakes
3) Maintains more even trim, less sensitive to loading position of what you’re carrying
4) Allows the boat to plane at a lower speed … and that is not only safer for smaller skiffs in bigger seas, but can allow for a smoother and safer ride

I LOVE the SE Sport 200 (https://www.sesport.com/Home.asp) the best! Rated the fastest foil on the market by Trailer Boats Magazine and Bass & Walleye Boats, giving your boat better speed, handling, and control.

I don’t think one ever gets more speed at WOT, in fact I lose up to 2MPH, but for me, the improvements noted in 1-4 above far out-weighed any loss of WOT speed … as I don’t run there anyway for 95% of my cruising. But I can certainly see handling improving to the point you could run faster in a given sea state or conditions that you could have without the foil.

#s 4 & 5 PROPs – Go to the website for Turning Point Props (https://turningpointpropellers.com/) and use their prop wizard/calculator to help you find the BEST prop. In my experience, until you get into a 40hp motor with some balls to it … forget about a SS prop.

#6 OTHER SPEED – The #1 best thing you can do for any small boat is lighten the load! I can’t believe the amount of weight some guys here on these forums are adding with their builds, albeit sweet constructs to be sure … but then I’m stunned, that they’re stunned, that performance with the little 15hp on the back has really suffered. Really … ?? Huh ..., LOL!

Within certain conditions, HP is HP, and I’ve only seen minor performance increases in smaller OBs when considering # of cylinders and not so much the displacement. And even there, it just might have been that the OBs with 3 vs 2 cylinders just ran smoother, thus giving ‘me’ a false sense of better performance. I’ve also only seen better performance on the higher displacement motors of the same HP class when the otherwise identical rigs were heavily loaded. Remember, each of us can buy a 25hp motor and your’s puts out 22hp and mine puts up closer to 28hp. Again, HP is HP …for the most part.

#8 EXPECTED SPEEDs – See https://www.rbbi.com/folders/prop/propcalc.htm

As with anything boating or women related … your experience may vary …

 

[25yamaha]

thank you all don't call me an idiot but has anyone tried sking/knee boarding behind a 25, how did it work? probably hard to get on plane

 

[turbotodd]

Thank you to every one who contributed my model number is c25elqr or something like that

That would be a commercial 25. Big block 25. Whatever you want to call it, it's roughly 500cc where the "normal" 25 is 398cc. Same powerhead as a 30hp, I think some of the Mariners used that same powerhead back in the 1980's. So yes, it'd be feasible to make it a 30hp motor with a couple mods that wouldn't affect reliability.

Skiing behind a 25? Tough question. Not sure it'd have enough guts to pull a skier up. But I have never tried it so.....

 

[25yamaha]

i had a freind who had the 1992 yamaha 30hp on a 16' smokercraft and he said they used to ski behind it... obvisouly it wouldnt be a speed boat but to take up time in the heat of the day it would be fun... would a hydrofoil help with skiing?