I have had some problems with my 40 yo, 2-stroke Mariner overheating on my last two trips and have decided to replace it. I have just bought one of the new Honda BF series engines. The old engine was 4hp and the only other post re F21 engines on this site described a 4hp outboard. I was wondering what other F21 owners use. I decided to go for the 6hp long shaft variant, as it did not cost much more then the 4hp and from what I have read the 4hp has the same single cylinder engine as the 6hp but is just detuned, same capacity, same weight, so didn’t see the point in the 4hp, I’m sure the F21 can use the extra power. I was limited to about 1/3 throttle on the Mariner or it would start to steam in the telltale, so don’t really know what the full 4hp will do in terms of pushing the F21 along. Interested in your experience if you have an F21.
My first 21 had a 2 HP Honda. Fabulous motor but not enough power for my needs. Way underpowered unless you are going short distance in still air/water. My second 21 has a wonderful 6hp 2 stroke long shaft electric start 90’s Yamaha. Best outboard I have ever owned. Starts every time with one burst of the electric start and plenty of power to make 5+ knots into wind and chop. I love that motor.
Thanks Lionel, that sounds good. I have fitted and fired up the Honda now but it’s too wild here for a sea trial at the moment. I don’t have electric start on mine but its very easy to pull start as it has automatic decompression on the exhaust valve. If it does as well as your Yamaha, I’ll be well pleased.
What prop do you have on it? I have a 4HP johnson and it is way better with a sailboat prop on it.
It is the standard for the engine type, 200x150mm 3 blade (7 7/8 x 5 7/8in). I don’t know enough about props to know the difference between a regular and sailboat prop. I assume something to do with speed, i.e. does the hull plane or not under power. So do I need a bigger or smaller pitch?
My first motor was an 8HP two stroke 88 Evenrude that was on the boat when I bought it. LOTS of power but terrible fuel economy and a bear to keep happy (ethanol fuel and all). Second motor was a 5HP Mercury 2 stroke. Really awesome engine: light, powerful, smooth. BUT, it too suffered at the hands of ethanol fuel. Third motor is a Nissan (Tohatsu) 4HP four stroke which starts reliably (assuming I start it at least once a month), is wonderfully quiet, doesn’t smell, gets twice as many hours from a gallon of gas, and has adequate power for any situation I have encountered. My biggest complaint about the Nissan is that I want it to have a higher thrust prop since it has top end I cannot use ( with more throttle the revs go up but the speed does not) and is a little anemic in choppy situations.
Hi Chadrider, yes I agree, my 4 stroke Honda is much quieter and less smelly that the old 2 stroke Mariner I replaced. I am still running the Honda in but was out today and had it at 50-60% throttle for a while, pushing against wind in chop, I was doing about 5 knots, so I am very pleased so far. Your top end loss may not be prop related. With a clean hull the hull speed of the F21 is about 5.5knts or 1.34*sqrt(LWL). You may get a little more than that with more power but not much and it will waste fuel. I doubt your 4HP is enough to get the F21 onto a plane.
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Hi Chadrider, yes I agree, my 4 stroke Honda is much quieter and less smelly that the old 2 stroke Mariner I replaced. I am still running the Honda in but was out today and had it at 50-60% throttle for a while, pushing against wind in chop, I was doing about 5 knots, so I am very pleased so far. Your top end loss may not be prop related. With a clean hull the hull speed of the F21 is about 5.5knts or 1.34*sqrt(LWL). You may get a little more than that with more power but not much and it will waste fuel. I doubt your 4HP is enough to get the F21 onto a plane.
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Ahhhhh, but on a few wonderful occasions my gunmount spinnaker was! Actually, the 8HP Evinrude would dig a big hole in the water if asked but, as you say, at the expense of many gallons of gas. I think that with a slightly grippier prop I could get better response to throttle on the low end without losing any top end (which I don’t have). Probably at the cost of a slight decrement in fuel economy over long motoring periods which is something I very seldom do.
Ahhhhh, but on a few wonderful occasions my gunmount spinnaker was!
…yes I’m still waiting for that, only had the gunpoint spinnaker up once and it was in very light air. Out of interest, what was the wind speed required for that?
It looks like your pitch is already the lowest it goes for that engine, and the “high thrust” props only start at the 8 hp level. The blades have more area as well as the pitch change. Maybe they are interchangeable. On the Johnson line the 6hp and 8hp were basically the same engine.
I’ve also got a 9.9 sailmaster that the boat came with, I could probably haul a skier behind the boat with that one! I figure if I ever go out on big water with the boat I’ll take that one in case I need more power to make it through currents and wind.
Newt,
On the day of the best experience,I would estimate 15+ true with more in gusts got the boat so I was having loong surfs down slightly oblique waves. Blasting along the Connecticut shore from Greenwich to New Haven (ENE), about 1kt of current with me, 15kts of wind from the WSW, we averaged nearly 8kts. That means the boat was over 7kts a lot of the time. The rudder was humming the whole time. I would soak down in the puffs and keep it surfing by tightening up in the lulls. It was a great ride! It all got interrupted by a huge thunderstorm just off New Haven.
Hkowalczyk,
Yeah, that figures. I look at the prop on a Torqueedo and think “oooh, I want one of those!” but I think the rev range on those is much lower. I remember the 4 bladed paddles that old Seagull motors used to have. Those things were about 4HP, cranky, stinky and could push a small house! That Sailmaster will buck the tide!
Have the 4HP Honda on mine; more power than I have ever needed, but I wouldn’t take this boat out in severe weather, nor so far off that I might get caught out. For close inshore, fair weather sailing, I reckon a 2HP auxiliary would do, and the difference in weight would make it much easier to unship. Handling 25kg over the stern is quite challenging, and mounting it whilst on the trailer overbalances the whole thing without the mast stepped.
If I want to be offshore, I go in our F35; interestingly, I can get 2+ knots using the dinghy lashed alongside with a Honda 2.2 HP in calm waters when the propeller falls off that one.
Castaway, hope you don’t make a habit of loosing your prop, could be expensive. I have a cheap electric trolling motor as a backup on my F21, probably 1.5-2hp. That brought me home when the Mariner packed up but I struggled to get 3 knts from it. Wouldn’t you believe it though. The circuit breaker tripped a couple of times before failing completely. Had to bypass it to get home.
Castaway, hope you don’t make a habit of loosing your prop, could be expensive.
It’s only happened twice! Both times in the same bit of Eastern Norway, though 7 years apart. We got to know the local boatyard quite well. I have dined out on whole sorry story.