Yamaha F70's

K

Keith Power

New member
I just had new twin Yamaha F -70's installed on my 22' cruiser. They weight about the same as the recomended F -50's. Seems to run fine after adding two Lenco trim tabs. Porbably will prop down also.Just checking to see if anyone else is running the same, or has any comments.
 
I think those engines are great. I don't run them but I would have if they had been available in 2009. When you get a chance to measure fuel consumption I'd love to know how they do. Good Luck with them.
D.D.
 
I'm considering those for a possible repower down the road a bit. I figure props would definitely change from those on my current 50's. Both horse power and gear ratios are different. I would also be very interested in performance and economy reports. Are they as quiet as I've been led to believe by one dealer?

One other thing: I noticed in the specs that the 70's have a couple of degrees less tilt range than the 50's or 60's. My current 50's just clear the water on full up when the boat is heavily loaded. Would hate to have engines I couldn't get out of the water when moored.

Thanks for any reports. From what I've read and heard, they are really nice engines. Good luck with them. I'm envious.
 
I was interested to click on this thread, as I have thought one of the "new" Yamaha 70's might make a nifty engine on my 22 (just one though!). Will be interested to hear how you like them. I would say that I'd like to know how your boat would run on just one of them, so that I could get some info on that, but then you'll have them propped differently than a person with only one, so that wouldn't be conclusive.

'course my F80 only has 50 hours on it, but that doesn't stop me from considering something else :D
 
How in the hell did you get somebody to mount twin 70s on a 22? I proposed twin Suzuki 60s some time back as they were the same weight as the 40/50 series and basically got shut down since the boat is only rated at 115 and that was only 5 HP more than the factory rating.

Definitely interested in seeing some pics and hearing how you like the boat with the twin 70s mounted.
 
I think too much power myself. One of the fastest C dory's around is Rana Verde and Chris runs a single 75. I was running hard to stay nearby in Powell. 90 on Kerri On is seldom used. You may have an issue with insurance. You'll likely be running them no where near wot ever as you now have a 38 knot plus c dory, you are definately going to see some squirely action at the top of your envelope. Keep tabs up. Best George
 
Definately raises a red flag over insurance. You need to declare the change of engines to your insurance provider, they will then change your file.
All is good until you make a claim. We all know that insurance company's love to find a loophole to avoid paying out. The fact that 22s are rated for a max 115 hp, might just be the loophole they are looking for.

Martin.
 
Just as a data point the Yamaha F-70 shows a weight of 257#. So, a pair would be 514#.

For comparison:

--My boat has a Yamaha F-80 (369#) and a Honda 8 (108#) for a total of 477#

--A pair of Honda 40/50 (215# each) would be 430#

I think if I were re-powering now, I'd be interested in either one F-70 with something like a Tohatsu 6 (~55#), for a total of ~312#; or a pair of Honda 50's coming in at 430#. From what I've read the 22 was designed with a older 70 hp 2-stroke in mind (I think they weighed around 250#) and handles nicely with a lighter stern (haven't tried it yet myself though). Although as has been proven by some intrepid 22 cruisers, they seem to take extra weight graciously.

Be interesting to hear how you like the F70 over time.

Sunbeam
 
I really don't see an issue and I think the transom will hold the weight and stress fine. Lots of boats have WAY flimsier transoms with 150-175 hp sitting on the back.

Yeah the insurance company might have a cow if the boat actually sank due to the motors, or you hit something at 40 mph you wouldn't have hit at 25 mph, or sank the boat because you couldn't control it, but for most claims (theft, bangs, bumps, even accidents), I don't think there is much the insurance company can say about it. Some companies will still give you a hassle I would bet, but they probably would anyway.....that is just who they are. BTW, I thought on boats of this size the hp rating was only a recommendation......Is this wrong? Someone please clarify.

I can only think of one good reason to repower with 70s, and that is because you probably can run the boats 25 mph on only one motor just fine. And to me, this has value if you run far offshore as while I have never had a failure, there have been times I have had to get the heck out of Dodge in a hurry due to weather. If one of my 45s had failed, things could have been different - although one of them will move the boat at around 14-15 mph wide open. If they can sustain that, it might be fast enough to run away. Anyway, I see the logic for sure and it would be nice to have a bit more if forced to run on one.

When you get her out on the water, please give us some information on the performance of the boat. I'd love to know how it planes with one engine and the speed you can attain on a single.
 
We have about 85 hours on our F70 powered Lund and really like the motor. I have dreamed of a pair on our previous 25 cruiser but am a bit surprised to see someone put them on a 22. A single F70 has been working good for at least one member of this group with an older 22 and I bet it would make a great motor for a 19 as well.

Ours is silent at idle and up to 1500rpm then very quiet below 5200rpm and belts out the power (plus a mean howl) all the way to 6300 when we want it. We see 5.5 to 7 statute mpg depending on winds and sea conditions with a running average overall of roughly 6.5. 5.5 last week in mile after mile of 2-3 ft chop hopping in the north San Juans.

We get 32mph at top speed with a load and propped for that load. With a light load and different prop we have seen 36mph on the GPS. The Lund is relatively light but still a wide and deep hull to push.

If anyone has questions or wants pics or measurements while considering this motor just let me know and I will try to please. We may even bring it to some gatherings so if you want to try it out, that is possible too.

Greg
 
I've been really admiring the F70 since it came out. Yamaha has done it again and really stepped up the engineering, showing a 4 stroke doesnt have to be a heavy pig. Honda and Suzuki R&D are now probably trying to catch up, just like with fuel injection over a decade ago.

I was comparing weight of our two honda 40s, to what twin F70s would weigh before Sunbeam posted it. At first, the extra 85#s seemed like alot.

We sometimes run our boat heavy, with a large cooler full of ice, food, beer, fish that could easily weigh 100+ lbs sitting against the motor bilge. A big guy sitting on that cooler, two deep cycle batteries, and both tanks full of fuel. Its never been an issue, and Ive never noticed a wake go over the bilge even with all that weight back there.

That extra 85 lbs seems kind of trivial, comparitively. Any number of arrangements from moving the cooler, batteries, fuel tanks elsewhere could balance that extra weight.

I for one wouldn't mind a few extra ponies when conditions are calm, and Im geting passed by every sport fishing boat in the fleet. Lightly loaded our 22' moves along great. Once its fully loaded with people and gear, those twin 70s kinda sound appealing.
 
I had sail boats all my life. The C-Dory is my first power boat and anything over 5 knots is fast to me. I still prefer puttering at 7 to 8 mph and smelling the roses along the way, knowing that I can boot it if the weather kicks up. When up on plane, 16 to 18 mph, the concentration level is more extreme watching out for logs, drift, and any other crap in the water. I have only gone over 20 mph once, and that was to get out of the way of a tanker in Haro Straight. I soon throttled back once I had cleared.
I understand that fishermen among us want to travel at the speed of light before that big salmon swims another mile further north, but that's another story.
Yup, I'm quite happy with my frugal twin Yami 40s watching the world go by. :wink:

Martin.
 
I had gotten water in my fuel this past winter , ( a mistake that will never happen again !! ) . I had to repower or not fish .As mentioned in the previous comments one 40 HP motor will not push my CD much past 8/10 knots in flat water. The 50/60 HP were about the same dry weight. I fish off the Lost Coast in Ca, not a good place to be if you do loose a motor. I will update this post as I get more info on the set up , good or bad. Thanks for all your comments. KP
 
A new Honda 115hp weighs in at 478 pounds. The twin 70's weigh 514 pounds. Weight difference 36 pounds. No kicker needed. I'm guessing a 10hp kicker weighs in around a hundred pounds. I think the power isn't as big a deal as the weight. The C-Dory Factory gave it's blessing at one time to the use of twin 175 hp Suzuki's on a TomCat as the were the same weight as a 150hp's.
A case in point our 23' Venture has a 150 which it is rated for weighs 65 pounds heavier than a 115hp. We are almost always heavily loaded for cruising with a dink, barbecue grill, Honda EU 2000 generator enough food and clothing for a month At 40 mph I think that with flat bottom although we have a keel that runs almost back to the transom the boat starts to get a little squirrelly. Chine walking? I like the extra power as I don't have to run the motor too hard to cruise at 20 or 30mph. It gets up on plane pretty easily. Running inlets riding the back of a roller in it's nice to be able to dial what you need. My point being if this boat is run responsibly I would not see a problem. As for the insurance company take that's not my department. Maybe he should ask the factory for their blessing based on the weight being less than a 115hp with a kicker
 
Keith Power":3tz004hz said:
I just had new twin Yamaha F -70's installed on my 22' cruiser. They weight about the same as the recomended F -50's. Seems to run fine after adding two Lenco trim tabs. Porbably will prop down also.Just checking to see if anyone else is running the same, or has any comments.
Click to expand...

I recently re-powered with twin F70's. I have less than 20 hours on them, but so far I'm extremely happy with them. Below is a fuel usage test I did. I've been surprised at what appears to be a slight improvement in gas mileage over the F50's. We'll see if it holds up under real world long-trip conditions. (Two Inside Passage trips of about 4,000 miles, total, produced a 3.3 MPG average with the F50's - with a VERY heavy boat in all kinds of water.) The sweet spot still seems to be around 20 - 22 MPH. Top end is obviously more, but I never ran WOT with the old engines.

I'm planning on changing to a 13.5D X 14P Stainless 3-blade at the 20 hour service. That should get the WOT closer to the 6300 RPM max, especially when loaded for long cruising.


12/26/13 Fuel Mileage Test

Outboards: Twin Yamaha F70s;
Props: 13.5 Diameter X 15 Pitch, 3-blade aluminum
Boat: Cape Cruiser 23
Load: 60 gallons of fuel; no water; moderate amount of gear; one person.
Gauge: Yamaha Digital Fuel Management Gauge
Conditions: Slight ripple, winds less than 5 knots
Calculation: Results are the average of two runs at reciprocal headings.

RPM MPH GPH MPG
0.7K 3.20 --- ---
0.8K 3.70 --- ---
0.9K 4.00 0.50 8.0
1.0K 4.40 0.70 6.3
1.5K 6.10 1.00 6.1
2.0K 7.60 1.80 4.2
2.5K 9.20 2.40 3.8
3.0K 12.1 3.50 3.5
3.5K 15.3 4.50 3.4
4.0K 19.9 4.70 4.2
4.5K 24.0 5.90 4.1
5.0K 28.2 7.80 3.6
5.5K 31.4 10.0 3.1
6.0K 34.8 11.9 2.9
 
Another note or two I meant to make in the post just above:

I mounted the new motors one notch higher than the old. I always thought the Permatrims were riding a little lower than optimal on the old motors. At planing speeds with the new set-up, the Permatrims are now covered with just the thinnest sheet of water - just as recommended. So far I've had no problem with the props catching air cornering or while bouncing around in some fairly sloppy conditions. Plus, most of the time the boat is likely to be loaded quite a bit more heavily than it is right now. Anyway, I'm not really into cutting doughnuts at WOT - so I don't think it will ever be an issue.

Another reason for mounting them a little higher was my concern about getting the motors completely out of the water at full tilt. As I noted near the top of this thread, the F70's have slightly less tilt range than the F50's. Well, the skegs clear the water by a good 2-3 inches, so I don't think they'll be sitting in the water even when the boat is fully loaded for long range cruising.

It does look, however that with the F70's tilted full up, I will not be able to run my generator on the shelf I built in the splashwell. The cowlings on the new motors are a little higher, and extend forward a little more than on the old ones. I'll just have to remember to keep the motors down when using the generator.

New_F70_s_01.jpg

New_F70_s_07.jpg
Cheers.
 
I always thought that the newer light weight Yamaha 70's would be the perfect motors for a heavier loaded 23' C-Dory or Cape Cruiser. I hope you love them. I guess loaded heavy it might not plane on one engine. But it's a nice feature to be able to trot along at displacement speed on one engine or troll saving some fuel as you go. Wishing the best of luck with your new babies. Are they any quieter than the previous engines?
D.D.
 
My twin 50 Zuzys make me go 30 mph which is a boat speed that scares the crap out of me. I only go that speed just for the adrenaline and only on glass water and only for a short period of time. That's just me.

I think the torsion factor on the top of the transom with twin 70's pushing would be a concern over the years. I hate any more weight on the transom than absolutely necessary as the 22's are somewhat tail heavy with any adequate power. Also, transoms are torsionally beat up more trailering than running on the water. Again less weight on the transom the better when trailering.

So for insurance reasons, long life of the boat, boat trim, and ultimately the safety of the captain and passengers, I see nothing but negatives fro putting 140 horsepower on the back of these nice cruising boats. I trust the designers who put the 115 hp limit on these boats.

I'm a bit surprised that a boat shop would expose themselves to the liability of overpowering a 115 hp rated boat.

But then there are people that think 600 hp in their chevy is cool for going to the mall.

Your twin 70's are definitely a reason to go to your insurance carrier before installation. I doubt they would approve before hand. My neighbor has the 600 hp chevy. He's a millionaire several times over and pays a huge amount under a special insurance plan for his rods coverage.

But in the end, its different strokes (I think that may be a pun) for different folks and as long a we are all having harmless fun, go for it.
 
potter water":2vf43kb8 said:
My twin 50 Zuzys make me go 30 mph which is a boat speed that scares the crap out of me. I only go that speed just for the adrenaline and only on glass water and only for a short period of time. That's just me.

I think the torsion factor on the top of the transom with twin 70's pushing would be a concern over the years. I hate any more weight on the transom than absolutely necessary as the 22's are somewhat tail heavy with any adequate power. Also, transoms are torsionally beat up more trailering than running on the water. Again less weight on the transom the better when trailering.

So for insurance reasons, long life of the boat, boat trim, and ultimately the safety of the captain and passengers, I see nothing but negatives fro putting 140 horsepower on the back of these nice cruising boats. I trust the designers who put the 115 hp limit on these boats.

I'm a bit surprised that a boat shop would expose themselves to the liability of overpowering a 115 hp rated boat.

But then there are people that think 600 hp in their chevy is cool for going to the mall.

Your twin 70's are definitely a reason to go to your insurance carrier before installation. I doubt they would approve before hand. My neighbor has the 600 hp chevy. He's a millionaire several times over and pays a huge amount under a special insurance plan for his rods coverage.

But in the end, its different strokes (I think that may be a pun) for different folks and as long a we are all having harmless fun, go for it.
Click to expand...

I have a 23 Venture rated for 150 hp. Is very stable at 30 mph, although I cruise typically at 20 - 22. (My uneasy feeling starts above 35, so I just don't go there on anything but glass.)

D.D. - The comparative noise level is very hard for me to judge. I've never tried any kind of actual decibel measurement - and the 50's are gone, so there's no way to compare now. At any rate, there's not enough difference for my not very good ears to detect.
 
NORO LIM":lnsmfr17 said:
I mounted the new motors one notch higher than the old. I always thought the Permatrims were riding a little lower than optimal on the old motors. At planing speeds with the new set-up, the Permatrims are now covered with just the thinnest sheet of water - just as recommended. So far I've had no problem with the props catching air cornering or while bouncing around in some fairly sloppy conditions.
Click to expand...

I'm glad you came back and added this. Reminds me that I want to move my Yamaha 80 up a notch, and as such it's nice to hear that with the Permatrims up near where they are supposed to be you're not having "too high" issues.

Nice that your 23 "supports" the twin 70's well. I like that engine, and considered a single one for my 22, but .... I think that might be just a touch small (and two is too much weight for my mental happiness on the 22). Nice match for your 23 though, with its more buoyant stern :thup
 
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