Twin 40s or 50s

[bridma]

Patti and Barry on C-Cakes made an interesting comment. They currently have twin 40s, but if they were to do it all over, would opt for twin 50s.
How does the equasion pan out, assuming twin 50s cost more, weigh more, use more fuel, but in return get more speed?
I have twin 40s and they seem pretty fast enough for me. But then I am fresh from sail where anything over 6 knots seems fast.

Martin.

 

[colobear]

Martin,

I don't have any rational specific reason for suggesting 50's, I just think it would allow me to cruise at a lower rpm hence, (I think) not working the engines so hard. We typically cruise at 13-16 kt's so top speed is not the issue. Les Lampman tells me the only difference between the 40 and 50 is the electronics thus no weight difference. So there you have it.

 

[T.R. Bauer]

There are identical engines dimensionally. The only cost will probably be to the pocketbook. I doubt they would burn a noticable amount more of fuel unless run wide open all the time. I have twin 45s and only burn 3-4 gph under normal conditions. I have been told a number of times the only difference in the 45s and 50s are the stickers.....Just like the only differnce between the early 35s and the 40s are the stickers.

I have also been told there are hard part differences (carb, if the have one, timing, cam, and other stuff) between the 40s and the 50s and the 35s and the 45s. How much difference there will be in the real world is open to discussion. My boat with a heavy load (4 people and 200-400 lbs of fish) still goes around 26-28 mph. Empty with just the driver, it will go in the low 30s and is frightening.....

In my honest opinion, I don't think you'll find a significant difference in actual performance between the 40, 45, and 50 hp motors on a CD 22 in most conditions.

 

[hardee]

Martin,

I have twin 40 Yamis, (like yours maybe) mine are carbed. I bought my boat used (very lightly -- 80 hours) and it was set up to go to Alaska by Jim, who had owned 33 previous boats. Jim's Dorie was to be his retirement boat. His plans didn't work out for him, but sure did for me. Anyway, Knowing now what I do, IF I were buying new, I would opt for twin 50's, the EFI version. Barry already cited the main reason, the engines would work less hard at cruising speeds. Maybe only 10%, but then that would just be that extra comfort cushion I like.

The second reason, the 50 EFI has the electronic output to feed engine data to my RayMarine MFD (multifunction display). That would give me fuel flow, and that would be a plus, because, as ypou may know, the FlowScan does not work reliably with the smaller flows that we have in our little engines

The third reason is that I believe a single 50 could get a 22 up on plane, if loaded and trimmed right. Not that I would want that as a usual practice, but if in an emergency....... Late last season I repropped, and I will try it again with my 40's but with 2 onboard and the old props (ProPulse "plastic") it was not possible to get up on step.

I believe the 40 and 50's are pretty close in size weight, and fuel burn so the main difference is the initial $$$ out. I have used them with a single up, and at slow cruise, the 40s do fine, (Jim knew what he was doing) so for me it is just the extra cushion that is the main difference. If I ever were to repower, it would be to 50's I think. It would definitely be to twins :thup :thup and it would (at least currently) be to Yamaha :thup :thup

Harvey
SleepyC :moon

 

[Chris]

Be careful about blanket comparisons in this horsepower range. 40's and 50's can be very close...and can be very different. Depends on the brand. For example...40hp Yamaha is 3 cylinder...50hp is 4 cylinder. World of difference. Things like displacement and alternator output are also important. Only way to really compare is to get out the spec sheets.

I'm with Barry...if it's Yamaha and twins...definitely go with 50's.

 

[hardee]

Chris, You are right about the comparisons. I did not look at specs, and am not mechanic enough to even think about the 3 vs 4 cyl differences. I do know the 40's are (or were in my vintage) carbed and the 50's are EFI. I think that the EFI is an advantage of the 50's as well.

Harvey
SleepyC :moon

 

[T.R. Bauer]

Patti and Barry on C-Cakes made an interesting comment. They currently have twin 40s, but if they were to do it all over, would opt for twin 50s.

Martin.

I suppose they should have said as they definately implied it, 50 hp twin hondas......As many noted, if you are going to change the original premis to a different engine series, it changes a number of factors.

In regards to the 50 hp has more torque than the 40 hp because it is a 4 banger is flawed reasoning. It has more torque because it has 10 more hp due to the extra displacement....the number of cylinders has nothing to due with torque at all - although typically all things being equal (piston and stroke wise)more cylinders means more torque. But it is pretty rare for those things to be identical from engine to engine to engine.

For a gross example, one could build a 4 cylinder motor with a huge stroke and coffee can sized pistons that would have WAY more torque than a 454 chevy. The problem would be balancing it, and once you did, well it would probably fly apart at 1500 rpms which wouldn't be very practical......Unless it was running a generator or a pump or something. But the point is, it would have more torque. However, it also has more displacement......which is why it has more power....

But then there are outboards.....hey this has the same block, the same pistons, the number of cylinders but has less power.....I always get the feeling when they do this that I got screwed out of power and efficiency. Why is it a 40 hp honda and not a 50 hp? Because you didn't pay enough as their probably isn't 10 bucks worth of difference between the two powerplants.......[/i]

 

[B~C]

honda 40 & 50 are the same block, 50 has a "hot rod " camshaft, larger valves & a bit different carb....just like high school hot rodding. With changes to the valve train and valve timing, torque and hp can be shifted around the rpm band but you're only going to get X amount of reliable power out of a give size of engine.

HP is a calculated number based on torque and time, hp= (trq x rpm)/5252 so if we had a lawn mower engine and spun it fast enough we could get 10,000 hp out of it. With that in mind, the 50 hp with the different valve train components allowing it to breathe easier at higher rpms develops it's rated hp at 6,000 rpm wheras the 40hp is rated at 5,500 rpm. I haven't seen any specs for torque for these engines but I would suspect the 40 hp would have a bit more torque due to the valve train. fer example, my collegue has a nostalgia dragster that puts out a bunch of hp. He lights that thing up in the shop and it spins up to about 12,000rpm in a heartbeat but it struggles to keep running at low rpm, lot of hp, but you sure wouldn't want that engine in your jeep or tow rig. If we took that same engine and installed a milder camshaft, smaller valves to give us higher cylinder pressures at lower rpms.....I suppose we should loose the blower and alchol fuel system too, it would make a good tow vehicle engine...

I'm rambling, 50 hp = a skosh more performance at higher rpm which may not be worth the extra money for a loaded boat used for cruising....for me, if I had the extra funds, I'd get the 50 because it's MORE POWER

 

[Les Lampman]

Oh boy...I'm almost, not quite, but almost afraid to wade in here. Sharks? What sharks?

This first part is coming from the Honda persepctive. The first of this size engine was 35 and 45 horsepower. Honda found out those numbers didn't work well with U.S. buyers so they reworked the intake system system and upped them to 40 and 50. In those days the 50 had a 1mm larger intake valve and a different cam shaft than the 40. The 50 also made peak torque at 4,500 rpm and the 40 at 4,000 rpm.

From a C-Dory standpoint the 40 made more sense for twins since the boat ran nicely on them, the peak torque rpm more closely matched the hull and speed characteristics of the CD22, and they cost less.

Fast forward to 2004 and than all changed when Honda decided having different parts in otherwise identical engines didn't make sense (any longer). The 40 and 50 became identical engines with the exception of carb settings.

It was a fairly moot point as to whether you ran 40's or 50's after than unless you intended to run over 4,500 rpm most of the time (not typical with a CD22).

The 50 does not use more fuel than the 40 unless you ask it to produce more power than the 40. As an example, if you're running at 14 knots and you need a total of 60 hp to do that then you get 60 hp from a pair of 40's or 50's. Same engine, same hp requirement, same fuel burn. If you start asking for hp that makes the 40 run much more than about 75% of rated power it gets inefficient while the 50 stays in its efficiency range longer. So if you push the boat to, say, 18 knots and now you need 70 hp the 40's are going to be out of their best range since you're asking a 40hp enging to produce 35 hp; the 50 will be happier.

I've always considered the CD22 a 14 knot cruise boat so I typically recommended a pair of 40's since they cost less and work well.

When Honda went to the EFI 40 and 50 things didn't change too much with regard to the difference between the 40 and 50; now it's just programming in the ECU.

In order to take advantage of the extra horsepower that a pair of 50's gives you you have to be running above about 17 knots. If you're doing that you're generally pushing the boat and most of us don't want to burn the fuel to do that regardless of whatever engine (or engines) we have on the transom.

If you want more speed out of your CD then I suggest you slow down to 6.5 knots for the next 20 hours of operation. When you go back to 14 knots it will feel like you're flying!

There ain't no replacement for displacement. A small displacement 40 is going to feel totally different than a larger displacement 50 if the manufacturer splits their line that way (Honda doesn't but others do). Just like a small 350cc 15/20 feels completely different than a 500cc 25/30; it's more than just the horsepower difference that's felt.

Back in the day the Honda BF40 was so "dialed in" that a pair of them got better fuel economy than a single Honda BF75 or BF90 at typical cruise speeds on the CD22.

Les

 

[bridma]

Wow, what great input. You guys are awesome. All my questions have been answered, and some.

Martin.

 

[Spike]

Hey Les
Gotta question for you. Since Honda and I imagine all the other big motor manufactors do is change fuel mapping to get those extra 10 hp. Does anyone make a plug in chip for EFI outboards like you can get for trucks? Would be intresting to be able to change back and forth between 40 & 50/ 90&115 and get some numbers. Just thinkin'

 

[B~C]

carbs, cams, what the hell was I thinking this morning, natch it's all done through the wonders of efi and computer controls....I must be stuck in the 90's, maybe because any of these boats built after....oh...say 1999 are inferior

 

[T.R. Bauer]

I run my honda 45s all the time at 5000 rpms if conditions allow. It results in 21-24 mph. It has a marginal impact on the economy of the boat. I like that speed and so does the boat. After 5000 rpms, it becomes a fuel sucking pig for some reason. The carbs must progressively richen at that point.

 

[TyBoo]

Along the same line of thought... I decided I'm getting a new kicker and it will be a Honda to match the big feller. I notice the Honda 20 is the same physical size and weight as the 15. Will the 20 do enough of a better job against the river current to make it worth the extra cost? The classic style 15 I had wasn't much use for trolling at anytime other than slack tide.

 

[TyBoo]

I run my honda 45s all the time at 5000 rpms if conditions allow.

I also run at 5000 most of the time (Honda 130). My 18th cousin said the Honda wouldn't care. I gain about 5 mph over running at 4500 and can zip along at 20 in all but the sloppiest of chop. I like it. Fuel is just as terrible there as lower rpm so the only additional cost is engine oil. It seems to burn oil at the higher rpm. Sometimes coming back across the bar I fudge it to 5200 and it uses oil quicker there than at 200 rpm lower. (Good thing it's not a diesel it might run away.)

 

[ghone]

There must be chips available. Chris on Rana Verda has a Yamaha 75 that runs like a 115. At Powell last year I kinda thought he'd chipped it and port and relieved and balanced and maybe a little nitrous there. He can scoot! Or just keeps the boat really light. George

 

[C-WEED]

Repower with twins? Since I always cruise heavy and the Yamaha high thrust 50 and 60 is the same block just make mine a twin high thrust 60. That should cover all the basics. Running on one engine or two... it should perform very well.