I'm not impressed....

South of Heaven · Posted: Mon Sep 28, 2015 9:08 am Post subject: I'm not impressed....

I just bought a brand new 4hp Yamaha, 4 stroke kicker (the pictures are in my album). I'm disappointed! I thought it would have adequate power to push me along in my 16 Angler; it barely does.
I tested it outside of the Boston Harbor along an island. There was obviously a good current but I still thought I could make some headway. Nope, nothing. Once I got back to the bay I tested it again. It was adequate there. My only concern is that I bought the kicker for emergencies when I'm away from the bay....this setup won't work. I'll probably end up selling this and going back to my old Johnson 8hp.

JamesTXSD · Posted: Mon Sep 28, 2015 10:15 am Post subject:

I had a 4 hp 2-stroke Merc that would push a 17' sailboat at hull speed. Loved that motor, sold it with the boat. I tried a 2.5 hp motor on that same boat (1500 pounds), and it would move it at 3 to 4 knots, although it took some time to get there.

I had a 5 hp Honda that was heavy, unreliable starting, and wouldn't move a dinghy (Porta-Bote) worth a darn. The dealer suggested that I try a different prop on it. There were a grand total of 2 props available for that motor back then. A different prop made almost no difference. I sold that motor with about 5 hours on it. The Merc 2.5 moved that dinghy at the same speed, BTW.

Just mentioning this to illustrate that it is more than hp... you might try a different prop. Positioning may make a difference - had an adjustable motor mount on that small sailboat, and too low or high made a difference in performance.

For discussion, the hull speed on a displacement boat is 1.34 x the square root of the LWL (length of waterline). On a CD-16, that would be 1.34 x 3.87 = 5.18 knots. Yes, I know the C-Dorys are not displacement hulls, but that should give you a ballpark estimate for what to expect from any small motor. That same 2.5 hp Merc would move our CD-25 at 2 to 3 knots (no wind or current)... it would also give you some steerage. (never tested in an actual main engine out situation)

Jim

Sea Wolf · Posted: Mon Sep 28, 2015 10:55 am Post subject:

Just a note about horsepower certification:

Somewhere back about 20-30 years ago, the standards for certification of hp changed:

Originally, outboards were certified to have X hp at the powerhead motor shaft.

After the change over, the hp was certified to be at the prop shaft.

I have a great little Johnson (Belgian made) OB that was certified at 2 hp in the old system, and 1.2 hp in the new, a "loss" of 40% !

Perhaps the loss is less in the larger motors, but hey...............!

However, the small motors do seem to vary a lot in performance, just the same.

I personally prefer motors that are two cylinder, water cooled, and with full F-N-R shifting, when available (but often not n the smaller sizes).

Just something to think about.

Joe. Teeth

rogerbum · Posted: Mon Sep 28, 2015 11:07 am Post subject:

Jim's point about hull speed is relevant. With an kicker, you will not get much above hull speed regardless of horsepower as you'll not get the boat on plane. I'd note that this weekend was a full moon with the moon at it's closest position to earth. We had some of our largest tidal swings of the year on the west coast and so did Boston - I see this weekend there was about a 12' tide swing in Boston. I don't know about the currents near where you tested the motor nor the time of day that you tested but I do know that around here a 12' tidal exchange can generate some currents of order several knots. For example, during the flood this weekend, the current UPSTREAM on the Columbia river near the entrance was about 4.5kts, maybe a bit more in some places (that was for a tide exchange of around 11-12'). So it may be possible that the performance you were experiencing is due to very high currents. Just out of interest, when you were drifting along with no power at all, what was the SOG?

Aurelia · Posted: Mon Sep 28, 2015 11:19 am Post subject:

I am surprised it is not enough. We ran a 2012 model 4hp Yamaha longshaft as a kicker on our 17ft (and wide) Lund. It pushed that boat well enough for us at roughly 4.5 knots. I also use that motor on a 12ft C-dory skiff and it would plane that boat with just me and the kid aboard. I would also suggest a different prop before you sell it.

It looks like they make 5 prop options for that model but there is no info on which is the stock supplied unit.

6E0-45943-01-00 PROPELLER (3X7-1/2"X7"-BA) 1 UR
6E0-45941-01-00 PROPELLER (3X7-1/2"X8"-BA) 1 UR
6E0-45954-00-00 PROPELLER (3X7-1/2"X9"-BA) 1 UR
6E0-45949-00-00 PROPELLER (3X7-1/4"X6-1/2"-BA) 1 UR
6E0-45952-00-00 PROPELLER (3X7-1/4"X8-1/4"-BA) 1 UR

If you are only using it on the 16, I would try a lower pitch prop like the 1st or 4th in the list above. That will deal with the loading better than the other options which would be better on a dinghy or lighter boat.

Greg

hardee · Posted: Mon Sep 28, 2015 11:44 am Post subject:

I had a 15 foot Montgomery sailboat, weight is right about the same as a 16 C-Dory. I used a Mercury 3.3 on that boat and it would run it at hull speed, About 5 knots, at about 2/3 throttle.

My take on what you are experiencing is that you are trying to drive a non-displacement hull. That equals more drag. You didn't mention if you had your main OB tilted up, or if the leg was down and also creating more drag. That little Yami will move your boat, but it is going to be working hard, and it is working from off center, so that adds to the work load. Were you measuring speeds? Water speed, or over the ground speed measured on a GPS? There can be considerable differences between those two speed measurements.

Jim is right, Props can make a difference too. Roger is also right, huge tides this weekend, and a really cool total lunar eclipse, Wink

which neither adds or subtracts from the tides, but the super moon position in orbit was doing it's thing on the water. Joe is right too, the power ratings changed and actual, usable, demonstrable power seems less per HP than we expect.

On Edit: Greg is right too, but he pushed "Submit" before I did.

I wouldn't dump it off the transom yet, Do some further testing. Try a lake, or sheltered bay at a slack tide time. Let us know the differences.

Harvey
SleepyC Moon

thataway · Posted: Mon Sep 28, 2015 7:19 pm Post subject:

First a small kicker will not always get you home, but it can get you to safety--where you can sort out the problem, and most times repair it.

Second, How was the motor mounted and what was the shaft length? If the prop was right next to the boat's transom, you would not get good water flow.

My Merc. 3.5 hp 2 stroke merc will plane our 9.2 foot inflatable, with me in it, and push the C Dory 22 at about 4 knots in calm water. (3 blade low pitch prop).

srbaum · Posted: Mon Sep 28, 2015 8:41 pm Post subject:

Greg is spot on concerning the prop. I have a 4 hp Yamaha on my 24'7" x 18' trimaran and it pushes the boat easily at hull speed at about 2/3 throttle. In order to make this work, I had to change to the 1st prop on Greg's list (above).
The remarks concerning tides/current are also accurate, as the tide swings due to moon and wind will negate my boat from moving fast when at extremes. Fortunately for the trimaran, if there is any favorable wind, the boat will sail faster than any outboard can push it.
Lastly, the new 4 and 6 hp Yamaha are the same engine, except for the carburetor. The 6 turns a bit more RPM. The 4 could be made into a 6 by switching the carb...

South of Heaven · Posted: Wed Sep 30, 2015 12:25 am Post subject:

Thanks for the replies guys.

Roger, I'm not sure what "SOG" means. "Speed on ground?" GPS term? But I totally agree with you about the tidal swing last weekend and the above average currents. DEFINITELY a factor.

To answer some other questions, in no particular order....

1. I have a long shaft and I tried different trim settings. Mostly I was trimmed all the way down though. (Maybe I'll try some more trials with the angle at half trim.

2. Yes, my main motor was down and shut off for my trials. I used it as a rudder. I definitely felt lots of drag and didn't like the way the boat turned. I think "tying" it into the main would be better.

A different prop sounds like a good idea too. I'll be boating all of October and can't wait to try out some different mods! i love the boat!

I've got soooooo many more mods in mind..........

rogerbum · Posted: Wed Sep 30, 2015 10:29 am Post subject:

thataway · Posted: Wed Sep 30, 2015 6:15 pm Post subject:

You want the kicker trimmed mid way, and in clear water--all of the way down is too much.

Good on the long shaft.

I would trim the main engine out of the water. There is a lot of drag with the prop. If you are very slow trolling--it would be fine to leave in the water. But as a "get home"…you want to steer with the kicker outboard.

Webminer2 · Posted: Wed Sep 30, 2015 9:27 pm Post subject: Kicker on 16 Cruiser

I had a Suzuki 6 hp long shaft an it pushed my boat at about 5.5 knots not fast but enough to get me home. Tide will effect the speed. In Charleston SC the tide flows 6.5 knots at times so the speed over the ground would be a negative 1.5 knots backwards. You just have to watch the tides and use them to your advantage. More horsepower is not the answer it's planning your trip.