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Author Topic:   minimum hp to plane 20' Guardian?
timbaho posted 03-21-2003 10:39 PM ET (US)   Profile for timbaho   Send Email to timbaho  
Hi All,
Does anybody have any experiance or an educated opinion on what horse power outboard it would take to plane a 20' Guardian grossing around 3000 lbs? I've decided on twins for repowering but I'm unsure of what would be sufficient power to plane on one motor in the event of mechanical failure of one outboard. Any advice would be well received. Thanks, Kevin
captbone posted 03-21-2003 10:58 PM ET (US)     Profile for captbone  Send Email to captbone     
I would have to say 140hp would be min with a light load. Possible 115hp but 3000lbs is alot of weight. Your twins are limited to twin 90, 115, and 140s anyway IMO. The 150's are too heavy and twin 70s are too light.
Barry posted 03-22-2003 10:45 AM ET (US)     Profile for Barry  Send Email to Barry     
Looking at my Catalog CD for 1991, it shows the max. H.P. for a 20-Guardian of 180 and the min. H.P. of 85. The Specs page shows that for a 20-Outrage the max. is 200 and the min. is 90.

Since BW defined minimum H.P. as the H.P. necessary to plane with a "light" load, you might want to go with the 115's.

Sal DiMercurio posted 03-22-2003 11:36 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Barry, the question is about twin engines, in case one fails.
If one fails, will it take one of the twin 90s - 115s hp etc to get it back on plane.
Not just one single engine.
Barry posted 03-22-2003 03:04 PM ET (US)     Profile for Barry  Send Email to Barry     
Sal, I understood the question. I guess I wasn't clear in my response. The point I was trying to make is that since the minimum recommended H.P. to plane is 85-90 with a light load, that you will have better luck planing with a single 115 (one of twins) than with a single 90 (one of twins). My reasoning is that having a second engine on the transom means the load already isn't that light. Depending on what else you are carrying (fuel, gear, people, ice, fish, etc.), how your engines are mounted, how they are propped, sea conditions, etc., more H.P. for the one working twin may make the difference between getting on plane or not.
Fishcop posted 03-22-2003 04:26 PM ET (US)     Profile for Fishcop  Send Email to Fishcop     

Twin 90hp (2 stroke) should work fine for you. I know of several 20' Guardians that have this combo and plane on one engine.
The correct props help.


captbone posted 03-22-2003 08:29 PM ET (US)     Profile for captbone  Send Email to captbone     
Depending on what model you choose, I would aways go with the highest horsepower for that model. The 90 johnson 4 stroke is the same motor as the 140 johnson 4 stroke. Most 90s are the same as 115s. 90's will work but if you are running heavy, as most offshore boats run, you will be greatful for the 115 or 140s.
timbaho posted 03-22-2003 10:02 PM ET (US)     Profile for timbaho  Send Email to timbaho     
Looking in the reference section on Yammie 90 2s, looks like there is a significant weight savings on the transom of around 100-150 lbs over the other outboards in the 90hp -115hp class. I do have the optional bulkhead panel with the freeflow doors in it for excessive water over the transom scenerio. Does anybody think the 3 cylinder would be the way to go versus the 4cylinder and the added weight? Shouldn't the 3 give me adequate power and better fuel range proped correctly? Just to restate what my major concerns are, I want to be able to plane and handle 4-6' seas on one outboard just in case the other fails. The desired cruising speed would be @40 mph with both outboards operating properly. Thanks, Kevin
timbaho posted 03-22-2003 10:07 PM ET (US)     Profile for timbaho  Send Email to timbaho     
what type are the twin 90's on the boats you are refering to?
Sal DiMercurio posted 03-23-2003 12:44 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Tim, your not going to stay on plane in 4 to 6' chop,...swells, yes, as long as you take them on the quarter or half, but not following or head on if their close together.
As far as "cruising" at 40 mph,....I don't think a pair of 90s will allow that, unless your way into the throttles.
Have a buddy with the same boat your talking about, had twin 70s,....a complete dog,[ wot, 35 mph ] went to twin 90s, does ok [ just ok ] but only fishes the Sacramento river, never the ocean.
If you want to "cruise" [ i say cruise ] at 40 mph, you better put all the ponies you can on her, or your knuckles will be bleeding from hitting them on the dash as your forcing the throttles forward.
Go max hp all the way, you will be much happier.
captbone posted 03-23-2003 12:58 AM ET (US)     Profile for captbone  Send Email to captbone     
Some people say the 90 3 cylinder Yammies are = to everyone elses 70hp. The yamahas just dont have the CC to make the torque as the other do. They make 90 hp but not the grunt of others, and that is what you need to get out of hole or out of the way of a breaker.
Fishcop posted 03-23-2003 12:18 PM ET (US)     Profile for Fishcop  Send Email to Fishcop     

Mercury and OMC. The Yamaha 90's are lighter, but are only 3cyl.
Sal has the right idea, flat water is no problem on one engine. But a 6' sea, you may want to get twin 115hp.
The weight on the transom should be your concern. With the bigger motors, your feet may get wet.


Eric posted 03-23-2003 11:32 PM ET (US)     Profile for Eric  Send Email to Eric     
With the 90 horse 3 cylinder, you probably won't get on plane unless conditions are perfect. You need torque to move that big hull. Remember that the 90 horsepower is power output at just less than redline. You've got to get the boat out of the hole first. The v4 90 makes maximum torque at a much lower rpm, too.
I believe a pair of 115s is the minimum for offshore use with your hull.
timbaho posted 03-24-2003 09:38 PM ET (US)     Profile for timbaho  Send Email to timbaho     
Thanks for the advice men.
timbaho posted 03-24-2003 09:40 PM ET (US)     Profile for timbaho  Send Email to timbaho     
Thanks for the advice men.

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