Kicker power versus weight on a Master Angler 20

[FishStretcher]

First- Hast to be quiet and 4 stroke. No exceptions.

I would use it as a 6MPH and under Marina/trolling motor and a get me home motor when the 1986, ~400 lb Yama 175 craps out. The Yamaha will be replaced by a 4 stroke 90 on a bracket in a year or two.

It looks like some 4 HP kickers are ~40 lbs, the 5-6Hp are 60 lbs. I think a 9.9 is too heavy? I have a 20 in transom cut, I think, and I am in some serious slop usually in and around Rhode Island and the Elizabeth Islands.

Any opinions on a 4 versus 6? I think a 100-120 lb 9.9 is too heavy.

[eggsuckindog]

I have the same set up with a 400lb Merc - can't see any of that working out

[cdavisdb]

The main factor kicker performance is torque, not horse power. 4 hp is plenty for a twenty if the motor swings a big, slow turning prop. I don't know any 4s that do that. I use a 8 hp Yamaha hi torque on my 25 seafari, its designed for sailboats, gets 5 knots at cruise into moderate wind and chop. My old 15 hp, with the biggest lowest pitch prop that would fit, would barely do 4.5 knots flat out in flat calm conditions on a smaller boat. That went down to zilch fast in wind and chop.

To my knowledge, the Yamaha 8 is the smallest hi torque moter out there. Its just under 100 lbs, pretty heavy for a 20.

[Fr. Frank]

I used a '71 9.9 Chrysler as a kicker on my Seafari. Weighed 67 lbs on the bathroom scale. It would push me at about 6-7 mph at WOT and 4 mph at 75% power. I changed that for an '84 15hp Chrysler (Ward's SeaKing) at 73 lbs which gave me 11 mph at WOT, and 8 mph at 75% power. (See the pic below)
With my 375lb 90 Optimax on a 20" transom, I got tired of the water that would wash over the transom in a following sea and run down the cable boots, making the pumps cycle on and off nearly constantly.

I dearly love having a kicker. But I won't replace mine 'til I raise the transom to 30" and replace my motor again, which may be years given how well my Opti runs.

[Bushwacker]

Connor's right - it's all about torque. Years ago Chrysler and Evinrude used to make "sail drive" models of about 6 hp similar to his Yamaha with lots of gear reduction and big slow turning props. Too bad they don't still make the old British Seagull. Very simple (some would say primitive) with exposed flywheel and gas tank (looked like a 1930's vintage outboard), no recoil starter, but very light (maybe 30 lbs) with LOTS of torque. Lots of brass and nickle and virtually indestructible. My neighbor had a 5 hp model, with a 5 blade prop about 10" diameter with about a 5" diameter hub and lots of gear reduction. With that thing on his dingy, he could TOW his 20 TON 42' Wheeler sedan cruiser! But I'm sure it wouldn't pass emissions laws and OSHA would go nuts with an exposed flywheel and starter rope!

[FishStretcher]

Based on the comments, I searched and these are available at defender.
http://www.tohatsu.com/outboards/6_4st_spec.html
A Tohatsu SailPro.

Maybe that would work.

[Blue_Heron]

So, just to complicate the issue, don't forget to factor in the hydrodynamics of the hull at displacement speed. Most of what I have to say here is from Dave Gerr's "The Nature Of Boats". But I've probably got some of it wrong because I loaned the book to someone who didn't retern it, so I can't check.

Every boat has a "hull speed", the most efficient speed for the hull to travel when it's in displacement mode. Hull speed is mostly determined by waterline length. When a boat moves in displacement mode it pushes a bow wave in front of it and drags a stern wave along behind it. This basically sets up a standing wave with a wavelength roughly the same as the waterline length of the boat.

The speed that waves move through water depends on their wavelength. Waves with long wavelengths travel faster than waves with short wavelengths. A short hull sets up a short standing wave that moves slowly. A longer boat sets up a longer standing wave that moves faster.

Hull speed is the speed at which the hull is in harmony with the speed its standing wave wants to travel. If you try to push the hull faster than hull speed, it tries to climb the bow wave and the bow of the boat rises. Because the boat is now trying to run up hill, it takes a lot more thrust to maintain this faster speed. Given enough thrust, the hull climbs over the bow wave and is then traveling at planing speeds.

So, in a nutshell, the kicker best suited for the boat is one that pushes it at hull speed while it is running at its most efficient RPM. Unfortunately, I have no idea what this is for a Seacraft 20.

Dave

[Bigshrimpin]

Having owned a 20 MA with a kicker (8hp Yamaha four stroke and then a 7.5hp Merc) and now an 18 with a 8hp Honda kicker, your problem is going to be the 20" transom. Both my 18 and 20ma had 25" transoms and I would take waves over transom. My motor is a lightweight 365lb Merc blackmax too.

[eggsuckindog]

thats my point - the boat can't handle 500+ lbs plus somebody sitting back there driving - buy a good VHF radio and a Sea Tow membership or you need a bigger boat

[cdavisdb]

I'm not familiar with the Tohatsu, but the pic doesn't look like a big prop. There is no substitute for surface area in applying power to the water at slow speeds; be a little skeptical. I'd try to find somebody using one on a boat similar to yours.

Connor