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Thread: Grumman 19' Sq. St. Outboard?

  1. #1
    Member RainGull's Avatar
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    Default Grumman 19' Sq. St. Outboard?

    I am looking into an outboard for a 19' Grumman Square Stern model.

    I am considering a 4Hp Yamaha 4 stroke primarily.

    What can you tell me about how the canoe will handle with a 2 HP Honda vs. a 4HP Yamaha vs. the higher HP with a lift.

    I am more concerned with deep water performance.

    Does a Grumman ever really get up and plane? What kind of speed can I expect?
    ----
    Also what material should I use to replace the transom wood? 3/4" Marine ply treated?

    Thanks.
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    Member Torpedoshooter's Avatar
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    I can only help on the last question ... as to the transom replacement I would use marine grade plywood with the edges well sealed with an epoxy product such as West System.

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    Thumbs up 9.9hp

    I run a 9.9 Merc with Lift and a Rockhopper on my 19' Grum.

    Works very well in shallow and deep...........more weight up front the better!


    To go against the current in most rivers the 9.9Hp is ideal!
    Alaska

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    Member RainGull's Avatar
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    I don't really want to run a lift or the rock hopper. Well rather I can't afford the additional expense and time. Raised transom, maybe, dolphin or the like no problem, but I'm hoping to run a slap it on and go and have decent performance.

    My father runs a 4HP Yamaha 4-stroke on his Old Town 15' sq. st. and says that it isn't too fast running wide open (not bad, just not super fast). It is the same beam as the Grumman and 4' shorter, so I don't know...

    The guy I bought it from thought his 6HP was a bit much without a lift or skirt etc...

    But I also wonder if I'd have to jump up to 10+HP to get up out of the hole and start planing?

    What does it take to get a Grumman on plane with a dolphin or the like?

    Am I going to be stuck at displacement speed anyways without a lift and 10+HP outboard? If so what does it take to maintain displacement speed and about how fast is that on the Grumman?

    Would it be worth getting a 10 HP short shaft 2 stroke without a lift?

    Just looking to put it into perspective without the buy it and try it approach. Not many Grummans running down here in Southeast.
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    Thumbs up motor for 19' Grumman

    In my opinion, a 2 stroke outboard in 10 or 15 hp. I use a Yamaha 15 hp short shaft with a lift, Dolefin, and rockhopper. My rig reaches 16 mph on flat water/rivers... hauling 2 200#ers and our gear. It cruises comfortably no matter the speed, and will quietly stalk along a river at +/- 1 mph. Economy is excellent.

    You can build up the transom to get the prop higher up. It has been used that way for years. I prefer the lift because when appropriate, I can lower the prop all the way down and have a little more economy and added stability (lower c.g with the powerhead lowered).

    10 hp and 15 hp outboards are usually built on the same motor, but in different states of tune, i.e., they are virtually the same weight, but the 15 has more power in reserve for those occasions when you're hauling a decent load and want to go upstream. All plus, no minus.

    4-stroke outboards are a good deal heavier than the 2-strokers of similar power rating.... and that makes a difference on the none-too-wide rear end of a 19' Grumman.... the difference is about 20%. I would have bought a 4-stroke Honda 15, but they weigh 101#. My Yamaha 15 weighs 78#. I'm more than pleased with my Yamaha.

    I believe I paid $135 for my Rockhopper.... and wouldn't go anywhere without it. I've heavily used my rig for the last 5 years with the original prop, which is in good shape. I carry a spare new prop, but have seen no reason to put it on. That isn't the story most guys can tell. A new prop cost approx $75 to $90 for a normal prop plus the pain in the ***** job changing props out in the woods. That makes the Rockhopper very worth while to me.

    Do a search on this forum, and you will find a wealth of discussion about the 19' freighters.

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    Member RainGull's Avatar
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    I have read through the archives and such, but there isn't a whole lot on the smaller outboards. Alaskacanoe running a 2HP was all I got on that front.

    I still want to know about hull speed semi-planing speed and planing speed with a Grumman loaded and unloaded.

    Anybody have any ideas about planing?
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    I can only help on the last question ... as to the transom replacement I would use marine grade plywood with the edges well sealed with an epoxy product such as West System.
    If you only coat the edges with epoxy, you will generate a rot-creating situation. Humidity and water that absorbs or soaks into the wood will get 'bound' at the epoxy/wood interface and then cause rot (moisture plus wood plus oxygen equals rot.)

    The quickest and easiest answer is to buy pressure-treated plywood and coat it with a good varnish.

    A better answer is to entirely cut out the transom, glass the faces with light glass (4-oz or 6-oz per yard), then seal the edges. To glass, coat the wood once with epoxy and let cure, then sand. Then lay the glass on it and squeegee (or black foam roller or similar) the epoxy right through the glass ...just enough to make the glass translucent. When cured, use a sander around the perimeter, sanding on the corner, to "cut" the spare glass off. Works like a champ. Now brush epoxy into all the plywood edges, re-brushing more on every couple of minutes, until the edges appear to stay wet. The epoxy soaks into the wood cells like microscopic straws. Let cure. Mix epoxy and either wood flour or silica filler to make a soft paste and rub this into the end grain of the plywood. Rather than having to coat several times to completely fill the edge grain, this will seal it up quickly and instantly. Once that's cure, give the whole thing a quick sanding with 100 or 120 grit and coat 2 more times with epoxy.

    Ideally, you would want to paint or varnish the epoxy to protect it from UV, but here in Alaska the UV damage occurs pretty darn slowly so it's not that big a deal for things that don't live outdoors in the sun 24/7. If you paint, you should be able to find some Pettit EasyPoxy primer and paint in your local boat shop. You can use other paints as well, but you will need the Pettit (or Interlux or System Three etc) primer to act like a barrier coat first. It's always a good idea to prepare a piece of scrap plywood by epoxy coating it while you're working on your project so you can test your paint or varnish on it instead. If it's not working, it'll just fail to cure or will cure very slowly. Be especially careful with alkyd enamels ...they're known for not curing on top of epoxy (but they do fine if you primer first.)

    If you use epoxy to coat your transom (and I recommend this), then make sure that you use a good marine caulk to seal up all fittings or screws or through-bolts the violate the epoxy coating. Something like 3M 5200 or SikaFlex 291 (or similar) work great, but avoid the so-called 'marine RTV' or 'marine silicon' type products. Always squeeze some caulk into any holes you drilled, then use it around the fastener as you install it, i.e. under washers or around screw heads (just screw right through a blob of caulk).

    Brian

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    Quote Originally Posted by RainGull View Post
    I have read through the archives and such, but there isn't a whole lot on the smaller outboards. Alaskacanoe running a 2HP was all I got on that front.

    I still want to know about hull speed semi-planing speed and planing speed with a Grumman loaded and unloaded.

    Anybody have any ideas about planing?
    Theoretically, a 19' canoe won't plane unless the motor is able to get the speed up to at least 6 knots (the approximate hull speed). At 6 knots, the canoe is 'barely' on plane, so figure 8 or 10 knots to truly plane. I don't know how much horsepower it takes to do this and it will vary a lot with loading conditions, but this is how fast you'll have to go (if that helps.) It also may be true that the shape of your canoe's hull may prevent ever planing at all ...you need to have a fairly flat bottom and straight runs aft (canoes always taper aft). Hard to say without trying it.

    Brian

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    Member RainGull's Avatar
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    I figured the approximate hull speed, (v=1.34 times the square of the waterline length) but like you say the hull shape has a lot to do with it. Reading in the archives WaterGremlin mentioned:

    "Even with an 8hp outboard the canoe would not get on step. I would have a 200lbs person in the front and the canoe would not stay in trim. Both of us would be looking at the sky. Eventually I added a dolefin to the outboard and with it I can plane out and skoot right along. I timed myself on Lower Fire Lake to the island and back, only took me a couple of minutes. I forget the exact timing."

    So 8hp properly trimmed will plane?

    "But somewhat odd to me is Alaska Canoes statements:
    I use a 2 hp to travel up both the Swanson river and the Moose river with 2 people and gear for a week, of course I come down stream on the way out if I have moose, but the 2 hp pushes us up as fast as we want to go, but then again this is flat water,with less than a 3 mph current."
    &
    "The Swanson is a very winding river, and very narrow in most places, so I am not going fast at all, The 2 hp pushes us up stream with no problem and My GPS says that I have had it @ 11.5 mph going up, as the fastest speed. I am sure that most of the time I am going only about 4 to 5 mph, but I am not at full power either. A river that is faster than say 5 or 6 mph would need a little bigger motor than my 2 hp to make really good time. If you are going in faster rivers, and going accross lakes etc. you better go with a bigger motor than the 2 hp."

    Coupled with my father's experience with his Yamaha 4hp 4-stroke, and it left me wondering if 1) the 2hp doesn't get you up to displacement speed (though I am skeptical of 11.5 since my fathers 4hp on a lake topped out a little above 8mph if his memory serves?), and I'm wondering 2) if the 4hp at WOT starts pushing against the transverse or diverse wave train but cannot overcome it. 3) At 6 or 8hp WOT a properly trimmed canoe overcomes the wave trains and gets up and planes, and then 4) at 10-15hp WOT it scoots along at top speed and maximum capacity (about 15-16mph)?

    Is that a fair representation from your experience at part throttle on a bigger outboard?

    I spend a lot of time in my head so this is as much curiosity as anything.

    I know I'm over complicating it, but I'm running a lot of fairly open water here and having a larger engine higher up doesn't appeal to me when dealing with a passing boats wake if it doesn't also offer a substantial advantage to me in my situation. I am looking for reasonable speed without open water compromise. Do I have that all turned around or is that logical thinking?
    Science has a rich history of proving itself wrong.

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    Thumbs up 19footer with outboard

    You are over complicating it....I did too when I was trying to make up my mind.

    2-stroke 10 hp and 15 hp outboards have been used for decades, up here, on 19' Grummans. The heavier power heads raised on a fixed transom can effect the center of gravity of the boat....it's an advantage to be able to run the motor all the way down, where appropriate....hence the lift extends the canoe's capabilities. It should be noted that with a fixed transom or a lift, the stability is good, though a bit better with the lift lowered.

    IMHO, a light, quality 2-stroke 15 hp outboard is the optimum for all round use...and it weighs the same as a 10 hp 2-stroke. Reasons to use a smaller, less powerful engine: lighter, cheaper to buy....fine for lighter duty/load use. Besides you can always spend more money later to buy the larger motor when you become convinced that your situation has changed or that your goals are more heavy duty.

    2-stroke vs 4-stroke: When it comes to power equipment, i.e., 4-wheelers, generator, pumps and outboards, I am a fan of the best Japanese makers, Yamaha and Honda. Honda doesn't make a 2-stroke outboard and their 15 hp short shaft weighs 101#, much too heavy for the rear of a 19'. The new Yamaha 15 hp 2-strokes are lighter by 23#, absolutely reliable and run a mix of 1 ounce oil/100 ounces of gas. To my old, battered ears, it seems as quiet as the Hondas I've ridden with. And it's very economical....one river trip of 170 miles, at speed, burned 16 gallons of fuel. IMHO, the small Yamaha 2-strokes are the very best of the breed. (And my wife loves her Yamaha piano.)

    When I first assembled my rig, I had a clear picture in mind of how I'd be using it. Now, years later, I'm using it in ways I couldn't foresee....and it's well suited for the new tasks w/o changing anything, because it was assembled for the maximum of utility.

    I travel open rivers, some weedy, some with lurking submerged logs, some rocky, some deep, some shallow, some swamps, over or around log jams. Last year I began taking a 2nd canoe (16' Wenonah Kingfisher) along - cataraft fashion - for off river lakes and ponds, exploring, and expanded capacity. And it makes a great, slippery tow sled for moving a dissected moose across the muskeg. This idea would not be as successful with a low powered outboard, but works great, after developing a bombproof rigging system, with my 15. I suppose my 19' Grumman could be termed a bush mini SUV for the river, and fulfills a wide range of uses admirably.

    So, for me, the Super Cub of the rivers is a 19' Grumman, 2-stroke 15, lift and skirt, Rockhopper and Dolefin. I keep going when the river boats turn around. I've spouted enough. Happy trails.

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    Member RainGull's Avatar
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    Thank you. Excellent response. I will suck it up and look at a few 15's.
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    Default 19 FT grumman

    when you use the canoe with out a lift the problem is shaft in water gets caught on logs, rocks, you have to get it off an it is out the back of the canoe,hard to reach this happends going up stream or down stream,
    weeds same problem have to stop, an get out an fix it
    But if you have a lift just pick up eng. an get a new bite on the water an go,don't have to get out of the canoe to do it ,al the eng's will work the 10/15 HP work out the best with a lift plus you can stand up an run the rig an see what is in front of the canoe [this is very inportent when going up or down streams ] SID

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    Hello Raingull,

    I want to give you my perspective on the motor for a 19' Grumman square stern.

    I'm running a 2 stroke Yamaha 8hp short shaft that weighs 60 lbs.
    I am using a Stingray XRIIIjr on the anti-cav plate.

    I have definitely had the canoe "on plane". With 400 lbs of people and cargo (excluding the motor weight), I've been able to achieve 14 mph (GPS measured). I have also loaded the canoe with about 600 lbs of people and gear and still been able to motor at 12.5 mph (once again with the GPS)

    I am not using a lift, although I have raised the motor mount up on the transom to keep the prop from being too low. I use my rig exclusively in lakes, not rivers. I'm not so much worried about hitting something with the prop, but if the prop is too low, the resistance of the shaft as it moves through the water will cause water push up the shaft, and actually start spilling over the transom. This effect occurs only at WOT.

    Hope this info is useful to you.

    Best regards,

    Jeff

  14. #14

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    If you read the Book by Dan O'Neil, "Land Gone Lonesome" he used a simular sett-up in his travels down the Yukon. A 19' square stern Grumman and a 15 hp outboard.
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