Outboard motor selection

[Clyde]

Some advice, please, from those of you who have OB's on your DS. I'm looking for a compromise between power and weight. Crew weight is approximately 400 pounds (not racing, obviously) so with the weight of the boat we're talking close to 1000 pounds. Not interested in electric. I'l looking at a Honda 2 hp which is half the weight of the Nissan 3.5. Another consideration is short vs long shaft. I'm thniking that long shaft is the best.

Thanks for your help.

Clyde

[algonquin]

There is quite a bit of discussion on this site concerning outboards. With that you will find a variety of experienced thoughts. In my case I feel that the 2HP would be underpowered in heavy winds, current, and chop. I run a 3 ½ HP standard shaft length that does very well in wind, current, and chop. Even though the shaft is standard length I haven’t hand any issues with cavitation as the transom is pretty shallow and the prop extends enough below the transom. My boat with equipment and crew is probably pushing 1150 lbs.

A thought about HP ratings. I wouldn’t reject using a 2HP versus something a little heavier and stronger as long as the prop design maximizes the HP potential. A bigger engine with an inefficiently designed prop can be outperformed by a smaller engine that has a prop designed to maximize the engines power potential. Brad

[jdoorly]

I am very unhappy with my electric trolling motor (Minn Kota Endura 55 [55 lbs thrust]) which draws over 40 amps and can only make 2.4 mph in calm conditions, so I've been looking for a gas replacement. I haven't found many used outboards on the internet and several of the new low hp motors seem to be different names but the same OEM (original equipment manufacturer, Hitachi).

I don't have any experience with Florida Outboards but find their low weight and low price very interesting compared to the Hitachi/Nissan/Mercury. This links to their 2.5hp water cooled 4 stroke for $625: http://www.ioutboardmotors.com/25hp4cyc ... ooled.html
They also have a 2.5hp 2stroke for $475, NEW!

But I concure with Brad, I'm looking for a 3.5hp. If I recall correctly the 1972 DS2 brochure claimed up to 8hp was OK, though the skip and crew probably have to hang off the forestay to balance the weight.

[Kevin F]

Replaced my 2.0 Honda after many years of service the last six pushing my DS 1. The Honda did a good job in average conditions with a 800lbs gross weight. Anything more rough it strained. Very nice at 27 lbs making it less dead weight under sail and easy to deal with. Now I am using a Merc 3.5 HP it was half the cost of a Honda ( 4 stroke), but 20lbs heavier. We will see if I get 20 years of service.

[Alan]

I've used an 80-pound Minn Kota Maxxum on my 1980 DSII. It was dreadfully slow with the stock weedless propeller and much better, but far from fast, with an open water prop from Kipawa Propeller.

Jay, Kipawa makes an open-water propeller for your Endura 55, so one of those might work as a stopgap until you get a gas motor. But I would vote for a gas motor in most situations.

I will say this for trolling motors, though: A Motor Guide Vari-Maxx 55 pounder, equipped with the factory open-water prop, will make an 80-pound Old Town canoe go like a bat, even with 350 pounds of people, 125 pounds of batteries, and 50 pounds of miscellaneous stuff on board.

[K.C. Walker]

Theoretically the daysailer transom should work fine with a short shaft. My previous boat had a pretty tall transom that was theoretically right for a long shaft but what I found was that it cavitated quite often. I think walking forward to deal with sails was part of it. I have a long shaft with the DaySailer and have never had cavitation but it seems long.

My motor compromise is an old Johnson 2 cylinder 4 hp. It's quiet and smooth and plenty powerful and only weighs 28 pounds. They don't make them anymore but they're very durable motors and the parts are still available. Mine is a 1972 and it still starts on the 1st or 2nd pull, most times. Occasionally it gets cantankerous so I keep a can of ether starting fluid for those times. It's a direct drive so you have no neutral or reverse and you back up by turning the motor around. That takes a little getting used to.

[jdoorly]

Thanks Alan, I've emailed my questions to Kipewa, and this certainly looks like a great interim solution for only $35.

[jdoorly]

Kipawa got back to me super quick, here's my email to them and their reply:

-----Original Message-------------------------------------------------------
From: Jay Doorly <jay_doorly@yahoo.com>
Sent: 2011-01-12 20:00:22
To: customerservice@kipawapropellers.com
Subject: Technical Question

I am very frustrated that my Minn Kota Endura 55 takes over 40 amps to drive my 17ft sailboat at only 2.4 mph in calm conditions, and in current or adverse winds it is hard to steer and even slower. I have been looking to try a propeller upgrade but I don't need the weedless feature because I use the motor to traverse channels from the dock to open water. Does the weedless feature reduce performance in open water? Also, I can understand how a three bladed prop can improve steering and bite, but I thought 2 bladed props were the most efficient?
Thanks, jay

Kipawa reply:------------------------

Hello,

The Kipawa Propeller being weedless is part of the design, it's just something you get with all of the other benefits of using a Kipawa Propeller.

The Kipawa Propeller has the same draw of power at full speeds just like the stock prop but our propeller is 10 - 15% faster because it pushes more water.
With that extra speed you can use your motor at lower settings and achieve the same speeds with out the draw of power.

You can try the Kipawa Propeller for a 30 day money back guarantee to see if there is any improvement. This if this doesn't work just give us a call and we'll pay for the return shipping and refund your card.

You may need to buy a bigger motor after that.

Thank you for contacting Customer Service.

Address:
P.O. Box 5974
Willowick OH 44095

Phone:
1-800-507-5866
-------------------------------------------------------------------------------
Unfortunately their reply is mostly standard marketing dribble, except for the 10-15% performance improvement spec. Let's see, 2.4mph + .24 is 2.64 for 10%, and 2.4 + .36 = 2.76mph if 15%. Well, I am looking to drive the boat to hull speed (5.3kn) so that is pretty dissapointing, but having better steerage against adverse weather is probably worth it. Also, the difference is speed between the "4" and "5" (high) speed settings on my motor is huge, it is doubtfull that I could make 2.4 mph in "4" without a 100% increase in power. I guess I'll wait and get one in the spring so I can try it out for 30 days.

[GreenLake]

Jay, I use a 40lbs trolling motor, and I believe I get up to more like 3kn with it at the highest setting. I don't load much beyond crew, batteries and motor, and very limited extra gear, so my estimate is something like 1100lbs for the total displacement.

I've switched to the Kipawa propeller and have to honestly report that the improvement is in a range that I would need a GPS to verify it. Dont' know that I could reliably ascertain even a 25% difference by "feel" unless I had two motors to switch between rapidly.

As it is, I did some timed runs, but the conditions are never repeatable enough to be conclusive.

As my other propeller was getting dinged, there was no extra cost for me, and the new propeller may have made things better - certainly not worse. As it turns out, I'm lucky to have made the switch, because the propeller key for the old prop was just about to give out, and I would have lost my old prop within the season

That alone was worth the $35 and one of these days I'm going to find a way to make valid comparisons between these two propeller designs.

I cannot report difficulties in steering, so I don't know what else goes on in your case. However, your amp reading (40) is more in range with 40lbs of thrust. Usually about an amp per lb. (I read somewhere) So I'm wondering whether you are not getting yours to the highest setting?

What's the cross section and length of your cables?

[Alan]

For whatever the information's worth, mine are No. 2 wire, 16 feet long.

[Alan]

Oh yeah, and also for what it's worth, the Motor Guide Power Prop (open water) prop has two blades. So does the stock weedless prop on my Minn Kota 80.

[jdoorly]

I installed a jack on the motor wires after cutting them down to 2.5 ft (I believe they are #12AWG), and a plug in the coaming near the motor, #8 AWG wires from plug to batteries (10ft), another foot or two jumpering circuit breakers and battery selector, and crimped and soldered all the connections.

I have been using the term "over 40 amps" because I can't remember what the actual reading was, either 42, 45, or 47 amps. But, I have a GPS and a speedometer, which are sometimes in agreement, so I'm confident about the speed under motor being 2.4 mph, or less due to wind or current. The steering problems occur as the speed drops during adverse wind and current. Current from the tide going in and out maxes at 1.5kn

There are 2 free ramps near me for access to Long Island Sound; both are about 2 miles upriver from the Sound (under RT95 bridges). But much better is Veterans Park ramp,in Norwalk, which I pay $130 a year to use. It, depending on the tide, is 1 to 2 miles of heavy traffic channel, meaning not a good place to sail. So I need 1 battery to go out and the other to come back in. One would think that 2 100AmpHour batteries should last more than 4 hours at 45amps. But that's not how they work. Once the battery voltage drops from 13.5 to 12.5volts, after an hour, the motor starts to go slower. And once the voltage goes below 12volts it starts to destroy the battery and it wont be able to take the same amount of charge in the future.

I did some searching to find equivalency between "thrust" and horsepower and I believe that 50 lbs of thrust is equal to 1 horsepower and 100 lbs thrust is 2 hp.

[GreenLake]

For whatever the information's worth, mine are No. 2 wire, 16 feet long.

According to this handy Voltage Drop Calculator this works out to a drop of 1.7%.

Mine is 6' of AWG#6, which works out to a voltage drop of 1.6%, or essentially the same. (Always assuming 40A). (I measure the diameter of the copper part of the wire to a bit more than .15" which should be AWG#6 according to the Table.

Jay's drop values for the 10ft run alone would be 4.3% and he has several connections and other loss inducing items. If the real Amperage is higher than 40, say 47, his voltage drop would be over 5% from the 10ft run alone, perhaps 7% overall. That could explain why he's not getting the power out of his motor.

The other reason for the speed to top out at 2.4kn instead of, say over 3kn, could be in the RPM compared to the prop pitch. If the boat already moves so fast that the propeller basically does nothing but keep up with the water rushing by it, then there would be no more forward thrust. Assuming a 85% slip rate, you can calculate the max speed if you know your motor's rpm value and the propeller pitch (supposedly 4" per Minn Kota site).

Steering should not be affected by current (unless there are eddies). The boat makes way through the water, which is what's needed for steering. However, you may not be able to steer "around" some object if the current is pushing you.

I once stayed 20mins "in place" in a tide current by motoring upstream. When I gently changed the rudder angle, the boat started to move "sideways" compared to a nearby buoy, even though it was still moving forward through the water. Eventually, the sideways movement got me out of the channel, and soon thereafter the wind returned and all was good.

Whenever your motoring speed matches the current, you can perform this "ferry glide". It's a neat trick when docking heavy boats in a current (dock parallel to the shore). Not really something you need for the DS

[jdoorly]

GreenLake I suspect your spot on once again, thank you. I will test this by measuring the voltage drop, and likely replace the #8 with #2 which is less than 2% drop. Thanks again.

[GreenLake]

Just found somewhere that the RPM for a 50lbs motor should be 1700. With that assumption, and with a prop-pitch value of 4" (from a Minn-Kota site) together with 85% slip, I believe the maximum speed at which the motor/propeller combination can deliver thrust is:

vmax = [1700 * 4" * 60 min / (12"/ft) * 6000 ft/nm)] *85% = 4.67kn