economy of 90 vs 115 on a CD22

T

tbag

New member
OK I am hoping to upgrade my 94 Yamaha 115 commercial 2strk to a 4strk in the next year. It is a bomber engine but it is loud, stinky and doesn't get great fuel economy (2.5-3 mpg). I would like to stick with a Yamaha but I am open to other ideas.

This topic has been indirectly addressed in other threads before but I would like to take head on. So I would like some real world insight from folks that have run both engines or have been on boats with both 90 and 115. Which is quieter, and most importantly, which get better fuel economy over all? I would like an engine that maximizes economy especially at planing and 20-25 knt speeds. From looking at Yamaha performance bulletins it looks like at Low RPM the 90 sips a little less gas but once you get up to planing RPMs the 115 seems to use less fuel. I am inclined to 115 since I have one now and a 4strk only weighs 35 lbs more and cost another ~$1000 new. But there is a 2005 90hp for sale in town for ~$4000.

Thanks for your thoughts and insight.
 
You will most likely find as I have that once you are into a "modern" 2 stroke or 4 stroke engine that you will see no difference between the 90 and the 115 in mpg. The reason is pretty simple in that your boat, depending on load, water conditions and winds/weather will have a comfortable off plane and on plane sweet spot. It will likely be significantly below WOT. So, with the 115, you will run a little less rpm and still get about the same MPG as you get with the 90 doing a few more rpm.

The difference in HP will only come to play if you need the extra 5% in getting on plane or the extra 5% for another mile or two per hour in an emergency. In those instances, there is no substitute for more HP. But in practical terms, 99.9% of the time you probably won't be able to have exactly the same load and load distribution and water conditions and density altitude and props and winds etc. etc. to be able to tell a whole lot of difference. Where as you are going from an older stink pot to a new high tech 2 or 4 stroke, if you stick with a 90, you will think you've gone to a 150 just because of the improvements in the motors.

My 22 is, I think, limited to 100 hp, which I take care of with twin 50 hp Suzies. I don't know for sure what the hull horsepower limit is for your year. But, it is more than just a transom weight issue. It is also limited by the twisting motion of the motor mount on the transom. (A reason that I don't play drag race with my 22).

Bottom line is that I doubt that even if your hull is only rated for 100 hp, you have anything to worry about with the 115. If I was only doing a single....Big mistake I think...(but there are endless arguments about that), I'd spend the few extra buck for the bigger engine.
 
Thanks for your input. I am not that silly, I always have a kicker motor for trolling and emergencies. Twins do not interest me. double the rigging, the maintenance and more $$ for the initial investment. Also twins are pretty rare up except for Cats.
 
I say I have twins, but just that they're fraternal :mrgreen: (i.e. I do have two engines, just that one is 80 hp and one is 8hp).

I loved 2-strokes when I was a kid and we had small ones on our skiffs - they still make me very nostalgic, and my 1960 Evinrude still runs like a top (!) - but on a C-Dory now it seems like a modern 4-stroke is pretty darned sweet :thup I bet you'll love your new engine.
 
Don't know what a 115 gets, but recently my CD-22 with a Honda BF90 got an avg. 3.6 mpg at just above 4000 rpm. This gave a speed of ~22 MPH. This was on pretty flat water with 2 adults for an overnight trip.
 
Nope, twins are very common on 22's. But lets not get this thread hijacked about twins versus singles.

But I can't resist: Would you rather fly on big jet that had a little engine on one wing and a big engine on the other? :):):)
 
I meant to say twins are pretty rare on CDs in Juneau AK where I am from. I have seen only a handful. And lest just say using your analogy that I for my boat I prefer one big engine and wings with a really good glide ratio.
 
potter water":3v22i7ux said:
But I can't resist: Would you rather fly on big jet that had a little engine on one wing and a big engine on the other? :):):)
Click to expand...

And I don't like to fly at all, so I'd say neither! On my boat, either twins, a main and a kicker, or just a main - I think they're all good options for different people and different reasons :thup
 
tbag
I repowered my 22 from a 90 Merc to a 115 Yamaha, both 4 strokes. I can say that the 90 was quieter at idle, and up to about 1500 to 1800 rpms and the 115 is quieter running at speeds. The mileage is so close as to not be much of a factor. But I very rarely get to within a grand of the redline. You are correct about the weights, again not to far apart.
 
Spike,

Thanks for the info. you are exactly the kinda of person I wanted input from So after the switch which engine do you prefer?
 
tbag
Setting the hp rating aside, I do like the extra 25hp, I have to say I like the yamaha. They are I feel both good products. I will say that there are some things about the merc I liked better such as a bigger alternator, but that was belt driven like a car. One more thing to check or have break. A person can get a Yamaha serviced or fixed just about anywhere nowadays. Other than a 6hp back in the 1960s the 90 was the first Merc I have had any real experiance with, but I have had several yamaha products. My 9.9hp kicker is a Yamaha, and I have ALOT of hours on it, and it runs great. I just redid the water pump on it in Oct. In fact one of my saxophones is a Yamaha, same company. I listen to alot of guys talk about motors and it is that Chevy vs Dodge vs Ford thing.
 
I am pretty much set on Yamaha. We have two shops here in town that work on Yamaha. Competition is a good thing. And I like my current Yamaha alot except I want to start going for some long distance runs . So what kind of mileage (or Knotage if you prefer) do you get out of the 115? And when do you appreciate the extra 25? I have never run my boat with a 90 so i do not know what that will be like.
 
I have a Yamaha 115 on my '22. Can't speak to performance v 90 because it's never had anything else.

I recently put about 70 mi RT on an overniter crossing Haro Strait to Sidney BC. I typically cruise at about 3700 RPM/15MPH. On this trip my fuel economy was about 3.5 mpg.

jd
 
While at Lake Powell this year, I had a conversation with Les Lampman (EQ Marine) about repowering. If I don't get this absolutely correct, I suspect Les will straighten it out. Basically, I am unhappy with the performance of my carbureted BF90 when we are at altitude. When I asked Les what he would recommend, he said a Honda 115, but with no kicker because of the weight of both engines. He is happy with the reliability and performance of that engine, to the point of not feeling a kicker is necessary.

I don't know if the performance and reliability of the Yamaha would be similar of better, but if you're set on a Yamaha, I would check it out. If you need a kicker, then I would be looking at a fuel injected engine in the 90hp range, and an 8hp kicker. BTW, the old Yamaha 8 was the best trolling motor I have ever used. Sadly, I don't think they make that model any more.
 
tbag
As I said I pretty much stay away from WOT so I don't know that I have ever used the full 115hp, but I like knowing it is sitting back there if I do need it. I don't run real heavy for the most part. Two batteries, kicker 2 adults, 50lbs of down rigger lead fishing gear, grub and drinks. I also keep both tanks full for the most part. I can squeeze just under 3 mpg at maybe 18 mph. To be honest I have yet to do anything with the 115 that a good well tuned 90 couldn't do. Yet. It's there.
 
I looked at the Honda 115 for a bit but it is just huge!! and I like to have a kicker for trolling so it wouldn't work. Spike I assume you mean 3 gph not mpg. cause 3 mpg is what I get. Thanks
 
Wandering Sagebrush":2qzxj3m6 said:
While at Lake Powell this year, I had a conversation with Les Lampman (EQ Marine) about repowering.... When I asked Les what he would recommend, he said a Honda 115, but with no kicker because of the weight of both engines.
Click to expand...

That seems like such a sweet engine. The specs look great, Les is convincingly enthusiastic (for good reasons), and I got a chance to go out on a boat with brand new twin Honda 115's. Nice! But then I think, well, it is 478#, and given the reliability of any brand-new engine in these times -- and if one is going to count on that fact (and I'm not saying it's a bad idea) -- then another brand new engine could be run with no kicker too, which in a way "makes" the Honda 115 really heavy again. I mean because that "other" brand-new, reliable single could be a ~350# engine (i.e. a 90 of various brands).

That Honda 115 sure seems sweet though! Almost makes me want a slightly bigger boat :thup
 
Wandering Sagebrush":zfzz64ec said:
When I asked Les what he would recommend, he said a Honda 115, but with no kicker because of the weight of both engines.
Click to expand...

The Yamaha 115 is quite a bit lighter than the Honda 115. A Yamaha 115 + 8hp kicker would be 484 (401 + 83) pounds vs. 478 for the Honda 115 alone.

Rob
 
tbag":nenup82j said:
But there is a 2005 90hp for sale in town for ~$4000.

Thanks for your thoughts and insight.
Click to expand...

tbag-

I have a 2005 Yamaha 90 4-S, and love it. No need for more HP unless you want to go Crazy Fast or run at 10,000 ft+ with the airliners. Great gas mileage. Runs like an auto engine in a new car.

If the $4000 one above is in good shape with moderate mileage (500 or less hrs), I'd buy it. At $4000, it's about 1/2 price! Twins and their extra expense are not necessary, IMHO, but that's a personal choice thing.

Joe. :teeth :thup
 
tbag


revised post:
Replaced my 98 Honda BF75 with a new Yamaha F115 on our 22 C-dory Angler in the fall of 2012.
I kept the 9.9 Honda Kicker which continues to work just fine.
After spending xxx money on the BF75 in 2011 and seeing the same issues resurface in the 2012 season I went with Yamaha.
They simply offer more service locations here in BC.
So far the engine has 8 hrs on it and I am very satisfied with it.
During the first 6 hrs I travelled 77.4 miles and used 59,9 litres (4.88 mpg)
but that was limited to lower RPM's, and varying the speed constantly.
In hour 7 and 8 I ran up to 6000 rpm, and a good portion varying between 3500 and 4500 rpm.
On that last trip I travelled 31.5 miles on 26 litres (4.58 mpg) with a load of 90 litres of fuel and 650 lbs of people and some light day cruising gear.
Currently I run a 13.25 x 15p prop and have reached 30.8 knots
at 6000 rpm on smooth Harrison lake. That was not even WOT.
I will try a 17p next and that should improve the fuel economy.
As for the noise, I find that the 115 is as good or better than the Honda.
The difference in cost between a 90 and a 115 was minimal.
My choice for more power is for west coast fishing, packing 300 lbs of ice, 3-4 people and gear for a four day trip.

The 115 Yamaha is only a few pounds heavier than the 75 Honda.
and the physical size difference does not hinder the kicker position at all.

Arend :thup
 
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