250-HR Yamaha 70 report

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Just a few things...

It's THE best winter engine! great starts, better for slow-cruise in choppy water (typical winter running) and not even a trace of condensation in the oil!

Definitely better mpg for all slow cruising!

It obviously makes a far better trolling engine than a larger engine it replaced, and I think it generally gets about 20% better (averaged figure on my all around use) fuel economy.

(on long trips with heavy loads trying to run fast, it might be getting the same economy as the F-115 it replaced)

Prop: Still experimenting, but for any Classic 22-foot C-D loaded lite to moderate, don't go over 13 pitch with 3 or 4 blade prop. 11 to 12 pitch is ideal.

Mercury 11P aluminum: Great prop but ventilates too much in rough water when light or too much weight-forward. The 11P Merc' Aluminum prop achieves at WOT: 24 mph and reach the maximum rpm with the boat packed for a long trip.

By going with a mere 70hp main engine, ideally you should have a prop for heavy loads and one for just taking day trips... one of only two dislikes by the down-size.

For the Classic 22 C-D at least, this light engine could work against you in trailing seas. It does ventilate more than the heavy 115 ever did with it's 18P prop. Just make sure you don't over-stuff the cabin (people and gear in big-water-running) and keep as much weight in back as possible.

I did find a favorite prop: 4 blade SS Solas 13P, but only after I bent the blades-down a notch! You can do this quite easily! :) I had to, after chopping through some huge bulb kelp fields wide open and later found the blades were got tweaked. :|

I had really great performance with the "Merc' Vengeance" 12P SS (when it was new) but after hitting a sand bar, the prop could no longer perform satisfactory --too much venting even after I hammered the cup back into it.

Best top speed is 29 mph light, with the 4B SS Solas. The Merc' 12P was just as fast but lacks 4-blade-smoothness and always ventilated more.

(the 4 blade also gives a better ride due to stern-lift)

Next prop will be the Solas SS 3 blade :) 4 blade only goes down to 13 pitch. Unless your just making day trips and light that way, I recommend a thin SS prop with plenty of cup in a 3 blade SS 12P. Solas props are thiner and a lot lighter than the Merc props i tried...
 
That's great info. 8)

Adeline is STILL running her Johnson 70.

She's real heavy with all the junk I carry.

14 X 13 aluminum 3-blade is good for around 5700 rpm and 27mph.

That's plenty fast for top end as I rarely exceed about 22mph even on flat water.

However, I struggle a bit in strong tides and crossing bars.

Mostly the 70 has been enough motor for me.

At one time you ran Red Fox with the Johnson 70 too.

Could you compare the two as far as performance and fuel rate ?

I think I read that the F70 has a recommended max rpm of 6300.

I'm guessing that it should be propped to run close to that on a heavy boat.

What rpm are you getting ?
 
Just a rough guess I'd claim the new 70 over the old Johnson would be very close to double the milage... I'm not totally sure though, cuz my original engine was pretty worn out. The new 70 is really impressive miser! But when heavy and trying to cruise fast, the efficiency falls off due to the flater prop I suppose... :|

I was pretty heavy for most of my trips last summer, i like to head out.... way way out sometimes :) The 70 handles anything you throw at it with a 11 or 12 pitch 3 blade. But if you want to go slow having to buck nasty water a lot, then the 11P prop is just perfect! I love a 10 knot cruise nowadays! :love

I've been doing a lot of prop trying outs, I still need to document numbers to give you an accurate rpm rating... the 11P alum' prop can reach max rpm 6300 heavy. But the dealer sez the engine only needs to reach 5500 rpm. I like that! :) The retuned 4B SS solas 13P never exceeds 5900 rpm when light and hitting top speed of 28-29 mph. Dealer sez that fine :)

(But this can turn into a major topic... I was trying some different trim adjustments when I was heavy with the 4 blade SS 13P Solas prop, it was amazing that I had a faster cruise speed with the tabs and engine trimmed all-the-way-down... :!: I guess taking a lot of weight off the transom makes a more efficient cruise in choppy water now with the nose buried in the on-coming waves! I was pretty amazed at the smooth ride, but it only worked at 12-14 mph. Anything faster just make the handling too wandery...)

My gut-feeling is the new 70 Y would be better for a post-Classic 22 models due to the different hull. I think the old Classics like and need a really heavy stern with some big tabs.... the way I once was :D

Perhaps the C-Brats will provide me with a post-Classic to do some testing... :P
 
Some good info here, im curious how twin 70s on a 25 would be. The only thing is last time i checked the 70 was not available in x long shaft. Maybe it will be in the future. Seems to me this engine/ hull would be a potent combo. A significant weight savings over twin 90s.
 
I know this topic has gone over time after time but I was looking at the SS 4 Blade Solas 15 pitch. I was wondering what you think the performance would be between the 13 pitch and 15 pitch.

Thanks

Kelly Lynn
 
Kelly Lynn":3pmtaggp said:
I know this topic has gone over time after time but I was looking at the SS 4 Blade Solas 15 pitch. I was wondering what you think the performance would be between the 13 pitch and 15 pitch.

Thanks

Kelly Lynn
Click to expand...

My best guess is that the 13"P SS 4B Solas would be best on the CD-22 with the 70 hp Yamaha, and the 15"P SS 4B Solas would be a better match on the same boat with a 90 hp Yamaha, generally.

Very heavy or very light loading, or high altitude use, could sway the results somewhat.

It also depends on how you drive and use a boat, and your own preferences for using rpm or torque.

Also, don't forget, unless it's changed, the 70 hp and 90 hp Yamahas are the same block (and therefore displacement) and will have the same performance at lower rpm until the extra 15 hp kick in at higher rpm ranges.

Torque curves, if you could magically get your hands on them, would look similar or identical at lower and mid rpm ranges.

And, as usual, Your Mileage May Vary!

My $0.02, again! :lol:

Joe. :teeth :thup
 
To give you a little more info. I have a 2007 Honda 75 hp. I am torn between the 15 or 13 pitch. I am looking for better top end speed. Thanks for the info.
 
unless it's changed, the 70 hp and 90 hp Yamahas are the same block (and therefore displacement) and will have the same performance at lower rpm until the extra 15 hp kick in at higher rpm ranges.
Click to expand...

That's the rub, Joe. :wink:

The F70 uses the same block as the F50 and F60 but shares a similar gear ratio to the 75/90.

Compare the displacement of the 50/60/70 to the 75/90.

Will she have the "oomph" to power through surging tides and bar crossings ?

On a heavy boat, will that strain translate to a shorter life expectancy ?

Yamaha_Midrange_Specifications_2012_01_05.jpg
 
Ye, Pete, your absolutely correct!

The F75 and F90 do have the same block, while the new F70 has the smaller block, and my muddy thinking didn't catch it in the rush to judgment! :embarrased

I was thinking of the older comparison, not the newer, and would definitely try the 13"P 4B first with the new, smaller block, F70 motor.

Thanks for the correction and extra information! :wink

Joe. :teeth :thup
 
15P SS Solas 4 blade is going to be way too much prop for any 22 CD with the new 70 ... go with the 13P (in 4 blade) and tune-it-down-a-notch if your into experimenting like that. :) it's easy to do, just take a 2x2 piece of lumber, lodge it tight against the trim/zinc tab under the main foil, and start tweakin on the blades :P --- a post-Classic 22 might run the 70 Yami Solas 4 blade 13 P better than my 22 though ... ?
 
We just ran our new Lund with an F70 for the first time this weekend! What a nice little power unit and even makes a sweet growl when you lay into it. Pushes the 2000lb (loaded) 17ft X 7.5ft Aluminum up to 35 MPH and jumps up on plane with no trouble at all. I will report back when I have more hours on it. I really would love to see a pair of these on the back of a 25 some day! Anyone ready for a repower?
 
I have never owned a 22 but from what I know of the planing character of these hulls, it doesn't take a tremendous amount of power to move them if reasonably loaded. It may work a little harder to get up on plane but that is a very small percentage of your running time, and once there, it should keep you running without working too hard. Our 70 runs really mellow and smooth from 4100 to 4800 so you find a prop to cruise in that range and it could work well. While it does make a wonderful, mean growl at higher RPM, that is probably an indicator that it shouldn't be run that high for long stretches of "cruising".

Our loaded 25 could just plane running only one of the twin 90s. So I always had a feeling that a couple of smaller motors could do the trick and save 350+ lbs of stern weight.

I think the load may be the real key and this motor plays a role in that load at a light 260lbs. It would be a great fit for a 19 perhaps and a good option for a 22 that didn't haul a heavy load all the time. Maybe two of them on a venture 23 would fun. The prop plays a big role as Redfox notes and that may allow you to improve performance to meet your specific needs using a smaller motor.

I think both the newer Honda 60 and Yamaha 70 are really nice power options if a person drops just a little bit of power ego and makes a smart decision. As the days progress, smaller and lighter will gain ground.
 
That's really helpful.
Adeline is still running her original Johnson 70 and she's faster than I need at about 26 mph topped out with a 14" x 13"prop.
90% of the time I'm happy with the power I've got.
It's only in strong tidal flows and bar crossings where she struggles a bit.
Still, the Columbia and Tillamook Bars aren't much of a problem. She just has to work on the big combers.
Cattle Pass can be a challenge.
I'd love to hang a nice, modern, fuel-efficient, lightweight motor on my transom.
When I go out I usually carry two
100 quart coolers full of ice, food, beer, bait, etc.
Add all my fishing gear, two downriggers & balls, batteries, 15 kicker and 4 horse dinghy motor/dinghy and I'm sitting low at the stern already.
The last thing I want to do is mount a much heavier outboard than my Johnson at about 250#.
 
Based on your loading, and based on the comment "It's only in strong tidal flows and bar crossings where she struggles a bit" I would suggest something bigger than a four stroke 70.

The Yamaha 70 is a great motor and I was really impressed with it on Greg and Cynthia's new Lund. But if you feel the Johnson 70 struggles "a bit" then a four stroke outboard of the same horsepower will struggle quite a bit. Four strokes don't have the low and mid range torque of a two stroke, so while in theory you may have the same top end with a 70 four stroke as a 70 two stroke (horsepower is horsepower), the four stroke may not be able to get the boat up on plane when loaded, and may struggle significantly in bar crossings.

Evinrude rigged a 29' boat with twin 250's- one Yamaha four stroke and one Evinrude E-Tec two stroke. When running on one engine, with the other engine out of the water, the Evinrude two stroke would get the boat up to 36 mph. The Yamaha four stroke 13 mph.

Why? It's not that the Yamaha is a bad motor (it's a great motor), it just doesn't have enough low end torque to get the boat up on plane and the two stroke does. Now I know that the hull shape (Deep V) amd horspower are vastly different from what you have now, but I think the results are indicative of what you could expect.

One wrinkle to add into this discussion- what year is your 70? Before 1988 or so engines were rated at the flywheel, they are now rated at the prop. So an old 70 might have only been about 65 at the prop. Maybe even less now if it's tired. So the new "70" might have more horsepower than the old "70". That may help some.

As always, just my observations, thoughts and opinions, and worth every penny that you paid for them.... :)
 
With 2 large coolers, oversized kicker, dinghy, and other fishing gear plus how many people on board, I would not consider your load to be on the light side at all so a small engine would be a bigger challenge for you.

See if your local dealer will allow you to trade it back in with minimal losses on a larger motor if the 70 doesn't work out. Maybe the rigging could be reused from a 70 to a 90?
 
Thanks for the great replies...

I guess 70 horses ISN'T the same 2-stroke vs 4-stroke.

One thing's certain though...Adeline is morbidly obese (like her skipper ???):oops: .

It's just that everything looks so good, I just have to bring it all with me. :disgust

Well, maybe I COULD leave just one case of beef-stew at home.

I think I'll run Johnny 'til he blows up.

Maybe by then Yamaha will have a new svelte F90.
 
If I were looking at a repower my 22 cruiser I would look seriously at the Yamaha 115. My 90 runs 20 mph at 4600 rpm.

I think a 115 would do 20 mph at about 4000-4200 rpm which is quieter and more relaxing cruise. I need to do 20 mph min and 4600 rpm is loud.
 
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