Help propping Honda 20HP 4-stroke

[xjma]

2006 Honda BF20 4stroke tiller with electric start and trim on a Lund WC-16 dlx (16' aluminum v-hull), no seats, strip down fishing boat. Battery for the electric start and stereo/lights under the pilot 'seat' area. 5 gallon gas tank usually located in middle of boat.

No tach, yet. With one person and some gear (anchor and lifejackets up front, cooler, tackle box, rods, etc) it can get up to 15 mph on GPS in moderately calm water, but with a second person (add 250) is won't go above 12mph no matter where that second person is located....less the further back they are. Three blade 9.25x9 prop, and from the sound of it the engine doesn't rev all the way out at full throttle. It really struggles in very rough water with no weight up front, real slow, sucks gas.

The holeshot is great, it just doesn't go so fast. Can somebody give me some tips without any tach info??? I'm going to get a tach!! Just drop down an inch or so in pitch?? Will that make it go faster or am I not going to get over 15mph with this motor?? Thanx!!

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

2006 Honda BF20 4stroke tiller with electric start and trim on a Lund WC-16 dlx (16' aluminum v-hull), no seats, strip down fishing boat. Battery for the electric start and stereo/lights under the pilot 'seat' area. 5 gallon gas tank usually located in middle of boat.

No tach, yet. With one person and some gear (anchor and lifejackets up front, cooler, tackle box, rods, etc) it can get up to 15 mph on GPS in moderately calm water, but with a second person (add 250) is won't go above 12mph no matter where that second person is located....less the further back they are. Three blade 9.25x9 prop, and from the sound of it the engine doesn't rev all the way out at full throttle. It really struggles in very rough water with no weight up front, real slow, sucks gas.

The holeshot is great, it just doesn't go so fast. Can somebody give me some tips without any tach info??? I'm going to get a tach!! Just drop down an inch or so in pitch?? Will that make it go faster or am I not going to get over 15mph with this motor?? Thanx!!

Hey bud I would definately do some prop research to get the most out of it, but that is a relatively small motor for a 16' Lund. I do love those aluminum hulls!

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

Nah but you know what, I think those boats call for a 25hp, so maybe you are going a little slower than you should. Hmmm, the Deep V of those boats seem to suck the life out of the smaller motors. I have a 16' Flatbottom Jon that will go about that same speed or a little faster with me and one other guy, loaded boat, and a 9.9hp.

 

[xjma]

Re: Help propping Honda 20HP 4-stroke

Thanx for the reply...I guess the 20 is a little small. Love it though, it's so quiet and reliable. When it's not rough out it sips gas. I guess I'll see if the lower pitch prop helps at all, but I'm really hoping I can rebuild a seized 25hp!

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

Thanx for the reply...I guess the 20 is a little small. Love it though, it's so quiet and reliable. When it's not rough out it sips gas. I guess I'll see if the lower pitch prop helps at all, but I'm really hoping I can rebuild a seized 25hp!

Well I wouldnt get too hung up on the speed thing. If it is reliable you are good to go. I dont know much about props, steele is helping me find one for my setup right now, but you may be able to get some more out of her. What is the max hp stamped on the transom?

 

[xjma]

Re: Help propping Honda 20HP 4-stroke

Well I wouldnt get too hung up on the speed thing. If it is reliable you are good to go. I dont know much about props, steele is helping me find one for my setup right now, but you may be able to get some more out of her. What is the max hp stamped on the transom?

I just checked on Lund's website and it's 30hp max.

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

I just checked on Lund's website and it's 30hp max.

Okay, so you are at the 2/3 mark. That, I believe is the lower limit of where (generally) you want to be with a boat/motor setup. It varies for different boats, but for the most part at 2/3 or less you aren't going to get the most desired performance out of it, and some boats wont even plane out at that 2/3 mark. Now I have seen it differ for different boats. I had a 14' aluminum flatbottom that had a tag for 10hp, had a 9.9 on it that did around 20MPH with two people and boat loaded to the max. I think the max hp tag rating is designed for the boat at full weight capacity, and to still get good performance. How much weight can your boat hold according to the manufacturer, and how much weight (persons, motor, gear) are you carrying. Adding a 250 lb. dude to the boat may be setting you at or over your limits. Once you get a tach you will be able to tell what size prop you need. I have heard on here the best thing to do is have the boat at a relatively light load and WOT at the upper limit(when choosing props) so when you weigh the boat down you will still be in the rev specs of the motor.

 

[xjma]

Re: Help propping Honda 20HP 4-stroke

Google says the boat alone weighs 425 and has a load of 1150#. On average I would say carrying no more than 600 pounds of people (two people at 400 total #s, plus a conservative 200#s of gear).

I haven't GPSed it but with a home-made tiller extension, with just one person riding in the middle the thing does fly. I'm hoping the Honda has the power to push everyone around!

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

That 20hp probably weighs close to the 200 mark. Id say you are near or at you max mark and that is why she is lugging down. Keep this in mind, I have a 16' starcraft v hull that weighs 600lbs. and it has a 65hp and calls for a 90hp! But it has a higher weight/people capacity, so when I load that joker down the 65hp seems not quite as stellar as she did with just me on it!! Id say enjoy her man, when you want company, you have to sacrifice some speed. My bud had a 14' bass boat that weighs around 6-700lbs. and a 28hp evinrude that at WOT moves us at a mere 20mph. His boat calls for a 45hp. But hey I dont complain, if you have to sacrifice how far you are comfortable going from the boat ramp until you can get a little 30hp, big deal. Put the 20 on the market, and when it sells go find you a nice 30!

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

Hey man count the splines on your hub because I have a little honda prop setting around at home with hardly any use on it. I have owned it for 5 years and never found a use for it. Ill check the pitch and if we think it will fit I will let you try her out. Like I said, it is just setting around.

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

Actually sorry, your motor weighs 101 lbs. That is incredible for a 20hp four stroke!

 

[steelespike]

Re: Help propping Honda 20HP 4-stroke

Has electris start and trim so more than 101 probably 110 but still mighty light.

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

Has electris start and trim so more than 101 probably 110 but still mighty light.

Sure is buddy! My 10hp 2 stroke is 75lbs.

 

[xjma]

Re: Help propping Honda 20HP 4-stroke

yep, it's way light for a 4 stroke! I think it's 110# dry, so add a # or so for oil and it's still pretty light. I'm thinking/hoping that I can dial this combo in a little better!

 

[sutor623]

Re: Help propping Honda 20HP 4-stroke

yep, it's way light for a 4 stroke! I think it's 110# dry, so add a # or so for oil and it's still pretty light. I'm thinking/hoping that I can dial this combo in a little better!

Yea it is amazing how much you can get out of the right prop. I just wouldnt plan on any miracles.

 

[steelespike]

Re: Help propping Honda 20HP 4-stroke

You said the boat was stripped does it still weigh 425?
We need to get down to cases; We need to get a gps speed
and the wot rpm.A Tinytach will get the rpm. Reasonable and easy to install.
A 20 hp is capable of 27- 30 mph on a light reasonably fast boat.
I think your 20 should easily reach 20 mph or more.
Prop calculator says that at 15 mph with a 9" prop and and 8% slip the motor is only turning 4,000 rpm
It appears it may not br planing. We had an 18 ft bare utility with an old 25 Gale that would plane easily with 6 adults aboard.
Your boat should do the same, plane easily that is.

 

[xjma]

Re: Help propping Honda 20HP 4-stroke

You said the boat was stripped does it still weigh 425?
We need to get down to cases; We need to get a gps speed
and the wot rpm.A Tinytach will get the rpm. Reasonable and easy to install.
A 20 hp is capable of 27- 30 mph on a light reasonably fast boat.
I think your 20 should easily reach 20 mph or more.
Prop calculator says that at 15 mph with a 9" prop and and 8% slip the motor is only turning 4,000 rpm
It appears it may not br planing. We had an 18 ft bare utility with an old 25 Gale that would plane easily with 6 adults aboard.
Your boat should do the same, plane easily that is.

Well maybe 'stripped down' isn't exactly accurate....it's a tiller boat with carpet over the bow hold that holds anchor, rope and a bunch of lifejackets, then carpet on two side boxes, one holds drywell (which is perpetually stuffed with empties) and one storage locker, then two benches in the rear. No seats or anything fancy, radio w/ two speakers up front and a battery, so 425# on paper but not like a bunch of heavy gear or bimini or creature comforts or anything.

I've got the GPS speeds...just no tach, yet! I'm fixing to get one, is the 'tiny tach' available from ebay legit?? I was thinking the trailtech one and just temporarily mount it that way I could use it for chainsaws, ice auger, etc. too. If tiny tach does the trick, I'll buy one today.

I agree, I think that this thing should atleast easily be pushing 20mph with 2 people in it!!! It may not be planing very well....most likely just prop selection or something else?? Trim position?? weight?? Comparing it to other similar sized boats and motors...I think it's not right. I know the 4stroke isn't going to sing like a 2stroke, but it just doesn't sound like it's in a happy sweetspot at WOT....sounds like it's working.

I'll get tach + gps and report back. Appreciate the responses everyone!!

 

[xjma]

Re: Help propping Honda 20HP 4-stroke

Damn, I had looked into a small digital tach before and was hesitant because there were some ~20 dollar tachs on ebay but I wasn't sure if they were going to be worth it or not. I thought these were the 'tiny tachs.' Well, I just looked them up and at 50 bucks I ended up going with the 38 dollar Trail Tech TTO instead with a replaceable battery. Will report back soon.

 

[xjma]

Re: Help propping Honda 20HP 4-stroke

So I've purchased my trailtech digital tach but have yet to use it as my brother lives 45 minutes away. For this 07 honda bf20, what is the ideal top end rpm range just for reference? I'll get top end RPM and GPS speed once I can get out on it with him. Thanx!!

 

[sasada]

Re: Help propping Honda 20HP 4-stroke

xjma...that sounds about right for speed. I go to Canada every year fishing and before i bought a fishing about we would rent the lodges lunds. They were VERY basic 16' v-bottoms equipped with a 20hp yamaha 4stroke. With 2 guys, gear, 6 gallons of fuel, and thats about it...like a said bare bones boat. They would top out at 15-16mph GPS. My fishing boat also a 16' lund but it has a carpeted deck, livewell, rod locker, raised front deck, trolling motor, 2 batteries, 6+ gallons of fuel, pedistal seats, re-enforeced gunnels, 50hp tiller, 2 guys, and gear will go 31-32mph gps. Whether my fishing boat is proped correctly who knows? I just know it does well all the way around and i dont have a tach for it. But as for your boat it seems to perform very comparable to the rentals i have used.