New Honda 90 vs. 100

[primative]

I'm looking to re-power my 22 cruiser, and see that the Honda 100 is the same weight as the 90. I would like the extra power of the 100, but I'm not sure if there will be any noticeable advantage in getting the boat to plane more easily compared to the 90 when the boat is heavy? I don't understand how the 100 gets the extra 10 horses nor why it requires the 91 octane as compared to 86 octane for the 90? Catalog states full throttle rpm range for 100HP is 5500 to 6300, and 90HP 5300 to 6300. Rated 100HP at 5900, and 90HP at 5800.

Does the extra horse power of the 100 only come into play for top end rpms/speed or is it helpful at lower rpms as well?

Have any of you switched from from a Honda 90 to the 100? your impressions?

I am not interested bumping the weight up to a 115, or using twins, so it will be between the 90 and 100.

Thanks,
Tom

[srbaum]

Tom,
Ask that question to David of Almas Only. David made the change from the carbureted 90 Honda to the fuel injected 100 Honda and told me that the difference is night and day.
His specific comments to me included words like much less noise at speed, very easy starting and much better milage. His short answer to the question of, was it worth it, was that he wish that he had done it sooner.

[primative]

Thanks Steve,
Will do.

[ssobol]

The BF100 gets you NMEA connections so you can look at the engine info on your MFD.

Seems odd that the only engine in the Honda line that requires 91 octane is the BF100. Every other one only needs 86. IME, 91 octane does not seem a fuel type available at most fuel docks I've been to. They usually only have 90 gas and diesel.

Maybe it's like my Pathfinder truck. It just says that premium fuel is "recommended for best performance". The truck runs fine on regular grade.

[croakz]

I went from a dying 2001 BF90 to a 2021 BF100. I would have been fine with a new BF90, but the wait time in May was July for the BF100 vs Sept for the BF90. Sportcraft Marina in Portland, OR did the work. They said the BF100 will run on 87 octane, but not make 100hp. I was fine with that, as long as it didn't damage the engine. My marina only has 87, so I add octane booster when I fill up. Seems to run fine. Honda Support said it should be fine, but reserved the right to blame lower octane fuel. I donno, I would have probably gone with the BF90 for simplicity sake if the wait was the same.

[thataway]

The 90 and 100 are basically the same engine, except a little tweak on the vales at high end (the 5900 RPM. The 100 needs the 91 octane to reach the 100 hp. Also there is NMEA 2000 available output from both the 90 and 100 according to Honda web site.

[croakz]

I do like the NMEA2000 compatibility on my new BF100. Installed the HD-4 gauge yesterday (Sportcraft was out of it and shipped it to me when it came in) and also plugged in my Garmin Echomap UHD 94SV, and I can now see all my engine info on my Garmin. Next up is to set up the fuel monitoring.

[journey on]

Honda has 3 engines with the same 1500cc engine: the BF75, the BF90 and the BF100.

The only differences are
BF75: no VTEC (valve timing as a function of engine speed)
BF90: VTEC
BF 100: VTEC and higher compression ratio

All have fuel injection and NMEA2000. And etc.

We have a Honda 150 for the last 15 years, great engine.

Boris

[primative]

Sorry for being slow to reply. Thank you all for your sound responses and questions. Some things have changed recently. I am retired, for one. What has not changed, we still love our C-Dory and this forum.
I have decided not to get the Honda 100, not that it wouldn’t work well, and as others have pointed out, choosing a new 90 in one of the main brands would be a good choice as well, with significant improvements compared to my present carbureted 90, at 22 years old.

Something Thataway asked relating to the Honda 100 resonated with me, "How much of the time do you run at 5800 to 6000 RPM?” 
ANSWER: Not very much, and when camping our boat is loaded heavy. The upper rpm band is not where I’ll be running my boat, so the extra power there wouldn’t be very useful. What I did not expect was that I would consider a 115 instead of a 90, because I assumed there would be an unacceptable weight increase. It turns out Mercury’s 115 CT (Command thrust) weighs 363 lbs. compared to Honda 90 at 359 lbs. Mercury's 90 CT and 115CT are the same weight. I believe the Merc Command Thrust model came out in 2014 or 15.

When you look at the manufacturers data for a Honda BF90, it states what the displacement is, the full throttle RPM range and the rated horsepower at a specific RPM, 5800 in this example. I am no expert, but what seems to be lacking is there isn’t a way to know what the specs are for the lower RPM range that I’ll be running. However, the California Air Resources Board (CARB) apparently requires reporting from various manufacturers of Spark Ignition Marine Watercraft (SIME) that includes both peak horsepower and peak torque.
Here is a link to the page with that information:
https://www.arb.ca.gov/msprog/offroad/cert/cert.php?eng_id=SIME&year=

Choose Spark-ignition Marine Engines
Then choose a year (data is available in 2020 for the ones listed below)
You may have to do a bit of searching to figure out what motor models correspond to the numbers in the Engine Family column on the CARB listing. Once you google them, you can see which motor model it corresponds with.

Here are motor weights from manufacturers and specs converted from the CARB site:

Honda 90 (359lb, 1.5 liter)
Peak hp is 89.8 at 5,800 rpm
Peak torque is 90.7 ft lb at 4,500 rpm

Honda 100 (359lb, 1.5 liter)
Peak hp is 100.5 at 5,900 rpm
Peak torque is 93.6 ft lb at 5,000 rpm

Mercury 90CT (363lb, 2.1 liter)
Peak hp is 91.2 at 5,250 rpm
Peak torque is 110.6 ft lb at 3,000 rpm

Mercury 115CT (363lb, 2.1 liter)
Peak hp is 120.7 at 6,000 rpm
Peak torque is 119.4 ft lb at 3,500 rpm

Yamaha 90 (353lb, 1.8 liter)
Peak hp is 95.2 at 6,000 rpm
Peak torque is 105 ft lb at 4,500 rpm

Yamaha 90 SHO 90 (353lb 1.8 liter)
Peak hp is 97.9 hp at 5,000 rpm
Peak torque is 103.2 ft lb at 4,000 rpm

Yamaha 115 (377lb 1.8 liter)
Peak hp is 115.3 at 5,800 rpm
Peak torque is 115 ft lb at 4,000 rpm

Yamaha 115 SHO (377lb 1.8 liter)
Peak hp is 123.3 at 6,300 rpm
Peak torque is 113.5 ft lb at 5,500 rpm

What stands out to me is the Mercs have large engine displacement, and strong torque delivered at lower rpms. Peak torque is low down in the RPM range for both Mercs. This sounds good to me.
Command Thrust (CT) models have larger gear cases, 2.38:1, and larger props.
From what we’ve heard these Mercs are DIY maintenance friendly.

The Merc 115 is the same weight as the Merc 90 with additional power. It would also seem that for a given boat speed the Merc 115 will be running at a lower rpm compared with other motors and hopefully quieter. I think the 115 will be the motor for me if getting the MercCT.

One thing that’s annoying is that the Merc Smartcraft data system has to be converted to NMEA to read it on our GPS. There are several options for this, which can be confusing and some of their gauges seem to be poorly designed. Rene thinks the super contrasty black motors are not as attractive on our boat. But function over look. We really appreciated our Honda, and it’s hard to think about not repowering with a Honda or Yamaha given the new advancements in those lines, but going by the specs, the Mercury seems like the best choice for my boat. The only thing that might keep me from making that decision would be dependability issues. Though they have been out since 2015, I haven’t seen much online as to how they are holding up.

[srbaum]

Tom,
Thanks for doing this homework for us, it certainly is very useful information.
On another note, my younger son's boat had a 115 HP Merc on it. His was not the high thrust version, but the powerhead and all other associated parts are the same. I helped him do the maintenance on it and yes, it was very user friendly.

[thataway]

Thanks for finding these torque ratings. For whatever reason outboard manufactures do not like to post torque curves for their engines.

I do know that folks who have used the Mercury CT 115 seem to be happy with the engines.

[primative]

One year later, here are our thoughts on the new Merc 115CT.
I would have never thought I would have bought anything other than Honda or Yamaha until I saw the California Air Resource Board info. If you haven’t already seen this data, look earlier in the thread.

RESPONSIVENESS
From what I have been experiencing so far, I like the motor very much. When I have been in lumpy/larger sea state the improved responsiveness is quite noticeable, of course this is relative to my older model 90. One note, we also switched to hydraulic steering at the same time, so some of the improvement may be due to that.

WEIGHT
The Merc 115CT is only slightly heavier than the new Honda 90 and we decided that is acceptable. Having the same lower unit as the Merc 150, it rotates a large prop, and gives you more prop choices if you need them.

TORQUE TWIST
When we took the boat out to break in the motor last spring, the almost empty boat immediately listed to port when going to full throttle. We didn't know why this was happening, but this "torque twist" is a very common occurrence for some power boats with outboards. The 115 CT has the Torque to do this for a 22 Cruiser.
We don’t normally use the full throttle as we did with the “break-in sequences”, which initially caused the boat to list to the port. Loading the boat heavier helps as well. I will be installing trim tabs, as this is the other (if not the most) recommended correction.

FUEL CONSUMPTION / NOISE
Because of the CT torque, we can cruise at a lower rpm which is quieter and more fuel efficient.
My experience so far is that the 115 is getting noticeably better gas milage than my former carbureted 90. Cannot say how it would compare with present day 90, which would also run quieter than the old 90, though at higher RPMs perhaps not as quiet as the 115.

POWER
The 115 gets our boat up on plane really fast! It does have a permatrim as well. We look forward to fully testing out the new torque once she’s heavily loaded for camping trips this Summer!

[WCF]

Primative - Really appreciate that you took the time to follow up on your old thread. For those of us considering re-powering soon, it is super helpful.


It seems there really is no replacement for displacement.