Does anyone have a rule of thumb on what the minimum horsepower motor they feel is adequate on a boat. I always went by my Dad’s rule of thumb that you should never be less than 80% of the maximum rated HP for any boat. Is that close?
Thanks. 
All depends on what you want to do with it
why would you want to underpower the boat. if you go too low it puts alot of stress on the motor to push the boat if it is that underpowered.
So you think that 80% of the rated horsepower is to low?
You will get several answers, the descision is ultimately yours. 80% and higher is better, thats what several boats had when I was looking. But there are many who want the maximum when they buy a boat. If you plan on keeping it forever, purchase what you want. If you plan on selling it at some point, go max.
Personal opinion here since I have never heard of any rule of thumb…..
Never under power a tiller boat. You could probably be ok at 80% on a console steer boat.
-J.
IMHO, always max the horespower out. You will get optimal performance out of your boat and your resale will be much better. Beware of the “dealer” package that frequently underpower their boats in order to put together a price point rig. 
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Beware of the “dealer” package that frequently underpower their boats in order to put together a price point rig.
Under power the motor, go lite on the trailer, under power the t-motor or too short of a shaft, under rated battery, weak jackstand just to name a few….
-J.
I agree. Go with the max ! Not only will it increase resale value, but you will enjoy the performance advantages
as well as better fuel mileage, because your not beating on it to try and get it up and going. My boat would’nt need a 250 Verado, but I can get all the perfomance I want at 3/4 throttle, save gas, but still have plenty of nuts left if I need it.
Kind of along these same lines I was curioous why on some boats the maximum horsepower allowed is higher for remote steering. For example my boat says max hp is 35 for tiller but 50 for a remote. Does anyone know the reasoning for it?
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Kind of along these same lines I was curioous why on some boats the maximum horsepower allowed is higher for remote steering. For example my boat says max hp is 35 for tiller but 50 for a remote. Does anyone know the reasoning for it?
You R the counter wieght 
Never under power a boat. The performance and resale will suffer accordingly. I do not like to see dealers advertising 16′ boats w/25 HP motors on them. People come in to talk to me and say what price will you have on that package? I tell them, I won’t sell you a package like that. I am selling boat packages that will give you YEARS of performance. My typical resale period with boat owners is 5, 10 or 15 years with a boat before they think about trading it in for another one. Ask questions of different dealers and take everything they tell you with a grain of salt. Also remember: where are you fishing, how many people will be in the boat, other added weight of accessories, etc. etc.
The boats I rig, go out of here with full horsepower or the next size down, unless specially requested by the purchaser.
It is expensive to repower a boat…
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I agree. Go with the max ! Not only will it increase resale value, but you will enjoy the performance advantages
as well as better fuel mileage, because your not beating on it to try and get it up and going. My boat would’nt need a 250 Verado, but I can get all the perfomance I want at 3/4 throttle, save gas, but still have plenty of nuts left if I need it.
That all sounds good but I think this is the first time I’ve seen someone say a bigger motor is more fuel efficient? I guess I don’t know much about engines, but I’m thinking my truck isn’t getting better gas mileage than a 4 banger at 40 mph just because my engine is working less than the little one. And isn’t that one reason people use kickers, better fuel usage than using the main motor? Do you have any links to information on that? I would be interested in reading up on that. Thanks.
Thanks for all the information. The boat I am purchasing is rated for a 135 Max HP and I was thinking of going with a 115 HP Mercury. Reason is I like the Merc and it doesn’t come in 135 HP. Any suggestions on a Model that is 135 or at least closer than the 115???
It really don’t matter ford chevy dodge = merc johnson evenrude yamaha
You just want something to push. 135HP and you are ready to go fish.
Richard
The main reason I run a kicker (besides safety) is it makes more sense to run a small, less expensive motor 8-12 hours a day, than use up big motor. 2500.00 vs. 15000.00. they all wear out sooner or later!
Walleyebry #993
I’m looking at the Ranger 1760 with a Yamaha F-115. Do you think this boat is under powered? It is rated for a 130 HP max, but they all have nothing over a 115hp 2 0r 4 stroke.
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That all sounds good but I think this is the first time I’ve seen someone say a bigger motor is more fuel efficient? I guess I don’t know much about engines, but I’m thinking my truck isn’t getting better gas mileage than a 4 banger at 40 mph just because my engine is working less than the little one. And isn’t that one reason people use kickers, better fuel usage than using the main motor? Do you have any links to information on that? I would be interested in reading up on that. Thanks.
To get an accurate comparison, you’d have to put your 4-banger motor into the truck and see how your MPGs compare.
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The main reason I run a kicker (besides safety) is it makes more sense to run a small, less expensive motor 8-12 hours a day, than use up big motor. 2500.00 vs. 15000.00. they all wear out sooner or later!
Walleyebry #993
Right, I would assume that is the main reason, along with being able to troll down to the speed you want. But I also hear people say better fuel usage?
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That all sounds good but I think this is the first time I’ve seen someone say a bigger motor is more fuel efficient? I guess I don’t know much about engines, but I’m thinking my truck isn’t getting better gas mileage than a 4 banger at 40 mph just because my engine is working less than the little one. And isn’t that one reason people use kickers, better fuel usage than using the main motor? Do you have any links to information on that? I would be interested in reading up on that. Thanks.
To get an accurate comparison, you’d have to put your 4-banger motor into the truck and see how your MPGs compare.
Good point. Or I suppose take a full size truck that has two different size v-8s and compare them. I guess I would think the big motor would always guzzle more gas no matter at what speed?
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I agree. Go with the max ! Not only will it increase resale value, but you will enjoy the performance advantages
as well as better fuel mileage, because your not beating on it to try and get it up and going. My boat would’nt need a 250 Verado, but I can get all the perfomance I want at 3/4 throttle, save gas, but still have plenty of nuts left if I need it.
That all sounds good but I think this is the first time I’ve seen someone say a bigger motor is more fuel efficient? I guess I don’t know much about engines, but I’m thinking my truck isn’t getting better gas mileage than a 4 banger at 40 mph just because my engine is working less than the little one. And isn’t that one reason people use kickers, better fuel usage than using the main motor? Do you have any links to information on that? I would be interested in reading up on that. Thanks.
I think what he is trying to say is all other factors the same, take a boat that is maxed out at 150hp. Run that boat at 40mph or about 3/4 throttle. Same boat with a 115 running WOT to hit 40mph. The 150 probably gets better gas mileage.
I would have to agree.
-J.
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I agree. Go with the max ! Not only will it increase resale value, but you will enjoy the performance advantages
as well as better fuel mileage, because your not beating on it to try and get it up and going. My boat would’nt need a 250 Verado, but I can get all the perfomance I want at 3/4 throttle, save gas, but still have plenty of nuts left if I need it.
That all sounds good but I think this is the first time I’ve seen someone say a bigger motor is more fuel efficient? I guess I don’t know much about engines, but I’m thinking my truck isn’t getting better gas mileage than a 4 banger at 40 mph just because my engine is working less than the little one. And isn’t that one reason people use kickers, better fuel usage than using the main motor? Do you have any links to information on that? I would be interested in reading up on that. Thanks.
I think what he is trying to say is all other factors the same, take a boat that is maxed out at 150hp. Run that boat at 40mph or about 3/4 throttle. Same boat with a 115 running WOT to hit 40mph. The 150 probably gets better gas mileage.
I would have to agree.
-J.
That could be. I’m just wondering if there have been studies done on this. I can’t seem to find anything about fuel usage at different RPM levels. How different is fuel consumption between 5000RPMs and 6000RPMs (or 3/4 throttle vs WOT)? Just curious.
There are performance bulletins out on Yamaha’s website. I can’t find them for Etec or Mercury.
It’s amazing how the fuel mileage increases for a motor running in the 3000 – 3500 rpm range. So, in theory, if you are running your 150HP closer to this range, you’ll get better mileage than a 115HP running 5500+ RPMs.
Thanks. That is interesting information. I compared the 150 and 115 on a bass boat. Looking at the MPH, the usage is pretty close between the 150 and 115. But of course they are on different boats so it really isn’t comparable. But it does look like running lower RPM is better. On the 150 running at 3000RPMs, you use 4.1 GPH. At 5800RPMs, you are running 15.9 GPH. That is a big difference!
Thanks for the information on the 135 Optimax. I will definetly be requesting this upgrade from the 115 I was looking at. Just another good reason this site is the Best. 
Now all I have to worry about is availability at said dealer.
As Jon stated BWB mag has lots of very usefull info on numerous Bass & Walleye boat manufacturers & motor manufacturers.They do head to head competitions,same boats with different manufacturers motors & will occasionally have 2 duplicate boats with 2 different hp motors from same manufacturer & rate them for holeshot, midrange punch & WOT (wide open throttle).Will give speed & mpg at each 500-1000rpm & optimum cruise speed.Which generally is 3000-3500 rpm for best mileage.If a person gets too underpowered they can find themself looking at a different prop, maybe a hydrofoil,jackplate & the list can continue.All trying to save $ instead of spending more repowering a underpowered rig.I watched a dealer selling a 16.5′ counsel rig with 50hp 4stroke & the boat was rated for 90hp.Told my father inlaw how good of mileage that 4 stroke gets. 
The boat was in his price range.I let him know that he was way underpowered on this rig & he should reconsider & shop around a bit.He did end up with the same boat while saving a few $ with a 70hp 2 stroke & it does come on plane just under 3000 rpm.He now wishes he had a 90hp.Hate to think what that boat would have took to get on plane with a 50 4 stroke,4000+ rpm. 
So much for the good mileage on the 50 4 stroker if you have to work it to death when running.Unless you just want to troll all day. You might want to consider finding a different dealer if they dont want to get you rigged with what you want,not what they have left over to sell you! Best of luck boat shopping. 
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