Motor swap

[Qrzed]

recently purchased a sweet 1974 Starcraft 16 foot ss with a older 60 hp Johnson. Unfortunately here in Pa. Lot of the local lakes have a 20 hp restriction. My question is would a 20 hp motor move this boat at a decent speed mainly going to be a fishing boat for me and the wife.was hoping someone could steer me in the right direction.

 

[Tnstratofam]

Our 81 16SS is rated for 90hp. We have a 75hp on her and she tops out at 35mph. My understanding is you want to power a boat at about 75% her max power at least. So I would think 20hp would probably move you fine, but at a decent speed I doubt it. I don't know how low in hp you could go when fully loaded with fuel gear and passengers before you can no longer plane the boat out.

 

[Qrzed]

That's what I figured someone would say. That's a bummer

 

[jbcurt00]

Decide what percent of the time you'll be fishing 20hp limit lakes.

If you use it for any type of cruising or water sports, a pre 1982 60hp is probably near the bottom of your 'fun' decent acceptable speed. A pre-82 50hp would be for me....

Fish different lakes different seasons?

I'd bet most of PA is going to be outside the ambient comfortable temps for cruising in an open bow runabout soon, for a few months. But possibly not for fishing. Rig for 20hp mid-fall thru late spring, swap to 50-90hp for the summer plus a little bit before and after. A 1.5-2ton engine hoist (149-199 @HarborFreight) has folding front suppirt spars so it only occupies a 2.5ftX2.5ft square in the corner of the garage. Makes removing/lifting/moving OBs very easy. Esp late model Johnsons w the lift loop pre-installed from the factory....

 

[Lowlysubaruguy]

I owned a 16 foot Pro Alaskan with a 25 HP ( an older one the OB not the boat boat was a 92) it would plane with just me in it. With two people it would not it ran fast enough to fish a few miles from the launch and I ran that boat many miles. Im thinking the Pro Alaskan probably weighed a little more than your boat it had side consoles windshield wood flooring large deck and a lot of storage compartments. I fished with 5 guys in that boat and the 25 HP OB as well. I hated that boat though. Kept it just over two years and sold it. You will never come off the water with a smile on your face from the sheer joy of speeding across the lake. But youll be motoring around just fine.

 

[Qrzed]

Never thought about that. Would changing all the controls and electrical connections become a problem?

 

[mr 88]

Highly unlikely that with the two of you and gear that you will get up on a plane. You might if you drop the pitch on your prop to get the motor within the recommended RPM range. One other option is a 25-30 hp with 20hp decals on it. Had a 15' Starcraft thst was pretty much stripped out and a 18hp and it couldn't get out of its own way. Needed a 4 cylinder 50 hp Merc to get it to move.

 

[ahicks]

Most 20's are going to be tiller steering I think. They're usually easily converted though. That get's you to the point shifting, throttle and steering would all be easy swaps. Not sure about the electrical connection on that small an engine. I know there's a 25hp with through hub exhaust that's capable as it's popularly used on pontoons. Not sure if there's a 20 though?

 

[mr 88]

Never thought about that. Would changing all the controls and electrical connections become a problem?

Generally speaking if you stick with the same manufacturer the controls and electrical hook ups should be the same for two motors of different hp.

 

[Scott Danforth]

a 20hp wont get you on plane

my suggestion, get a 10hp kicker for the lakes with a 20hp limit.... and pull your prop before you launch

local lake here has a 20hp limit. a buddy fishes it with his bass boat that has a 225 merc on it. he has to take his prop off the big motor and he just uses his trolling motor.

check your local AHJ (authority having Jurisdiction) at the lake and see if that is an option

 

[jbcurt00]

An even better option if permissible ^^^

 

[David Young]

Re paint the motor cover Johnson white then paint '18 HORSEPOWER' in big letters on the cover

 

[H20Rat]

local lake here has a 20hp limit. a buddy fishes it with his bass boat that has a 225 merc on it. he has to take his prop off the big motor and he just uses his trolling motor.

check your local AHJ (authority having Jurisdiction) at the lake and see if that is an option

They are strict in your area! We have HP restricted lakes also, but I have never seen anyone remove a prop. As long as the big motor is tilted up and left that way, no one will bother them. (and even then, the HP restricted lakes are quickly disappearing, they are going to no-wake. You can make a 20hp fairly quick and annoying in the right configuration, no-wake is hard to get around.)

 

[BWR1953]

A 20HP motor may actually get your 16' tinny on plane. It wouldn't be fast, but it would be on top.

My 16' Starcraft Kingfisher "almost" got on plane using just an 8HP Johnson with my wife, the boy and my big carcass on board. Plus a cooler full of ice and all our fishing gear. A 20 would have definitely gotten it up there.

 

[oldrem]

Re paint the motor cover Johnson white then paint '18 HORSEPOWER' in big letters on the cover

I was thinking the same thing

 

[82rude]

Until i joined this site i didnt even know motor size restricted lakes existed.Worst ive seen up here in ontario is in some provinical parks they allow only elect or just canoes.Tnstratofam my 76 ss160 is rated for 85 and i have a 2011 60hp etec and she will hit 34 gps .Even with a massive load she will hit over 30.

 

[Beagleville]

I bought a StarCraft 14.5' last year with a 25hp Johnson and it wouldn't plane with both my wife and I in it (would with just me). I replaced the Johnson with a 40 hp Merc, end of problem. HOWEVER, my StarCraft is a medium V hull, whereas your older one is probably a flat bottom (viewed from the stern) which would make it plane easier. My bet, though, is that 20 hp just ain't going to do it. Plus, if you plow around at full throttle you'll use an awful lot of gas for the distance covered.