Outboard Hp Vs speed

[Bonwitc0]

Hi.<br />I have a 10Hp Mariner Magnum 2-stroke mounted on a 16ft Bonwitco troutfisher 475 (double skin fibreglass). I have noticed that if run at full throttle with just me in the boat it will gradually plane. But. If laden at all with either the usual 100lbs of fishing gear and/or a second person it just cuts through the water. What would be the effect or benefit of using a 15Hp or 20Hp? Would the boat go faster when laden/unladen? The manufacturers plate on the boat states the maximum Hp is 25Hp? <br /><br />Thanks<br /> Brian

 

[phatmanmike]

Re: Outboard Hp Vs speed

i think you know the answer to this....<br /><br />more hp, faster speed.<br /><br />if its rated for a 25, get a 25. that lil 10 is an anchor

 

[Bonwitc0]

Re: Outboard Hp Vs speed

I like your style Mike. Short and to the point. Will the speed difference be noticeable with a 20? e.g. twice the power = twice the speed? (I don't know the answer, honest).!! I'm a Pike fisherman who has recently discovered that it's handier if you have a boat. A lot of the Loughs over here have limited bank access, so a boat gives you more access to remote places. Bank fishing in the winter is the done thing for Pike over here.<br /><br />Thanks for the help Mike.

 

[Scaaty]

Re: Outboard Hp Vs speed

Originally posted by BrianSp:<br /> Will the speed difference be noticeable with a 20?

You bet! It won't double your speed, but it will leave your shoes on the floor and you in the backseat when you nail it compared to a 10

 

[Snowdrggn]

Re: Outboard Hp Vs speed

Me thinks a brick will fly if you put enough power on it!!!!<br /><br />

 

[a_bullfrog_a]

Re: Outboard Hp Vs speed

how fast for a briggs stratton 5hp on 14 ft trihull?

 

[Winger Ed.]

Re: Outboard Hp Vs speed

Originally posted by a_Bullfrog_a:<br /> how fast for a briggs stratton 5hp on 14 ft trihull?

I think it'd go about as fast as you can walk while running it on nitro.<br /><br />But---<br />I may not be the right person to ask, I've got a 150 on a 16', and its too small.

 

[steelespike]

Re: Outboard Hp Vs speed

While I seldom walk while on nitro I have to agree.About a brisk walking speed.

 

[vetstudent]

Re: Outboard Hp Vs speed

While I seldom walk while on nitro

I think he meant the Brigg's on nitro not you!!! <br /><br />I thought the same thing until I read it for the second time! hehe<br /><br />As for the original question: I had a 7.5 merc on a 14' flat bottom that crawled... Upgraded to a same size boat with a 18 hp Nissan. It absolutely flew compared to the little merc... well until I got the 40.<br /><br />HP and speed have a direct relationship as long as all other variables remain same/similar. Pretty basic physics.<br /><br />You'd probably even notice a good difference in upping to a 15. You'll really notice with a 20 or 25 though! If you're thinking of buying another one I wouldn't even consider less than the 25. You'll be happy with less (temporarily) and then you'll be asking this same question again... "I've got a 15, if I put a 25 on it...." <br /><br />Brent

 

[JasonJ]

Re: Outboard Hp Vs speed

I say just stick a 25 on there. You'll have plenty of juice when you need it, and there is no law that says you have to run it wide open. Better to have too much power and not need it then to have not enough and really need it.

 

[ivar]

Re: Outboard Hp Vs speed

Originally posted by BrianSp:<br /> Hi.<br />I have a 10Hp Mariner Magnum 2-stroke mounted on a 16ft Bonwitco troutfisher 475 (double skin fibreglass). I have noticed that if run at full throttle with just me in the boat it will gradually plane. But. If laden at all with either the usual 100lbs of fishing gear and/or a second person it just cuts through the water. What would be the effect or benefit of using a 15Hp or 20Hp? Would the boat go faster when laden/unladen? The manufacturers plate on the boat states the maximum Hp is 25Hp? <br /><br />Thanks<br />Brian

You might not get double the speed when running alone, but the speed might even be tripled when running fully loaded. <br />I agree with the others, get the 20 or 25HP. Running a bigger engine at part throttle will be better than running that 10hp at full throttle alll the time. Less wear on the engine, less noise, less fuel used etc.

 

[Mercathode]

Re: Outboard Hp Vs speed

You'll think you have a new boat with a 25. Don't go a hp less!

 

[Bonwitc0]

Re: Outboard Hp Vs speed

Hi Gents.<br /><br />Got a 15Hp as a trade-in for the 10Hp Magnum. It planes a lot quicker and easier and will now even plane when we have it packed with all the fishing gear. A new problem though is that at full throttle (when it's planing) the water is threw up around the bottom of the power head and comes in over the back of the boat? Could it be that now it's planing and sitting higher in the water that the outboard needs lowered? Should I cut an inch or two out of the transom? Can't fathom this problem out? Any suggestions lads?

 

[WillyBWright]

Re: Outboard Hp Vs speed

Could it be that you have a longshaft motor on a shortshaf transom? If that were the case, the leading edge of the exhaust housing is plowing thru the water. That part of the motor doesn't go thru the water very efficeintly and blows a lot of spray forward and even into the boat. You might actually have to raise the motor. The plate above the prop should be about level with the bottom of the hull.