How’s it gonna push it?

[Blvr]

Im mounting a 1961 Johnson 40hp RDS23 on my 1990 19ft Lowe aluminum deck boat. Bought the boat used and found the Johnson 88hp had a badly grooved cylinder so i don’t know how well it pushed it around.
Just going to fish and swim off of it. How do you think it’ll do? Thanks for replies.

 

[Sea Rider]

A 40 HP will push, plane well depending on the number of boaters and load. To take the max out of that motor will need to tach it as usually will be loaded and dial a prop that makes that motor to run to at least middle of its wot rpm range. Start taching current prop and then go from there...

Happy Boating

 

[roffey]

Im not that familiar with that boat but... going from 90hp to 40 and pushing a 19 foot boat would be a good A to B boat. It will get you out on the water and fishing but might take a bit. Having said that any day on the water is a good day.

 

[ahicks]

I have a '93 19' with a 70 on it, and another '94 22' with a 120. The 70 does a pretty good job considering the size of the boat, but personally, I would go no smaller. I think you're going to find that performance with a 40 will be weight sensitive. OK when lightly loaded with just you aboard, but maybe struggling with the several people it's designed to carry. The 40 would work as well as it does due to the great big very shallow V bottom, and the fact it's a pretty light boat.

Maybe use the 40 while hunting for a suitable (larger) replacement? My thought anyway..... Best of luck. -Al

 

[racerone]

It will go SLOW and the world needs a lot more of ----GO SLOW-----The 40 will struggle to get it on plane.-----Rebuild the 88 hp at your leisure.----Nothing to it

 

[Sea Rider]

The OP plans going to fish and swim from it, apparently solo boating. If the combo is used lightly loaded a 40 should plane that combo well provided that the motor runs towards it's max wot rpm range. If that motor is not tached the OP will never know if current ptop is doing its homework right or not, could be lugging the motor without knowing. A tach will tell and a spot on prop maximization should follow..

A boat is rated for max HP motor on transom and max number of passengers. If don't plan to use it with full passengers capacity, don't need the max HP motor rated for...

Happy Boating

 

[southkogs]

Years ago I had a 50HP on the back of a boat rated for 100HP (16').

With me and maybe my lightest kid on board, after a little runup, the 50 would get it on plane. But think "following sea, tail wind and boating downhill" to make it happen. Most of the time we were just a barge "putting" here and "putting" there.

If you're not going long distances, or don't mind just lumbering your way around, it's not bad at all; kind of a nice lazy ride. If you're in a hurry ... you're gonna' hate it.

The only addition that I'll toss in: my boat was pretty light and the 50 did fine maneuvering. BUT, with just a 40HP on your boat, depending on the weight you could wind up with a fight getting it to go where you want in windy or choppy conditions. You'll have to test that out some on a calmer day ... see how confident you are that the 40 maneuver you around. It'll push it (just like a kicker motor would, and better), but controlling it in weather might be another fight.

Welcome aboard.

 

[Old Ironmaker]

I have a buddy down the lakeshore that has a 22' pontoon boat with a 15HP Mercury clamped on the back. He uses it exactly what you are going to use yours for, fishing, swimming and plain relaxing. He doesn't go far from shore and when he does go out it is as slow as molasses in January. He picks his summer days carefully and everyone has a blast on it. Boating is supposed to be fun, fast or slow, no matter as long as it's fun. As far as a 60 year old 40 I doubt it still is close to 40HP by now. Who cares as long as it runs well. We all lose some power by the time we hit 60.

 

[Sea Rider]

For recreational boating purposes propping right any motor to run at lest middle to max wot rpm range was not known in the good old days as it's now a days. If both 15 and 50 HP motors described on posts 7 and 8 would have gone through a spot on prop maximization your comments would have been more positive regarding both boats water performance running under powered motors on both applications. Propping right any motor is a day/night boating experience..

Happy Boating

 

[mr 88]

For what it's worth a 1961 was rated at the crank ,not the prop like today. So with it's age and todays rating I would say your closer to a 32-35 hp than 40. The correct prop as noted above will help the engines life as you would not be overloading the engine ALL the time , but as far as any kind of top end performance I highly doubt it will make much difference in your particular case . You are will be grossly underpowered for anything but putting around with any sort of payload on your boat.

 

[Texasmark]

Im mounting a 1961 Johnson 40hp RDS23 on my 1990 19ft Lowe aluminum deck boat. Bought the boat used and found the Johnson 88hp had a badly grooved cylinder so i don’t know how well it pushed it around.
Just going to fish and swim off of it. How do you think it’ll do? Thanks for replies.

Shopping Craig's list up in the Rust Belt where Johnnyrudes were popular back when the 88 was prime, you'll find numerous used engines of the era at reasonable prices. If you aren't mechanically inclined to rebuild your 88 then this may be an option. You can always list your 40 on Craig's list when finished.

Or if speed isn't a necessity, use the 40.

 

[Blvr]

All great replies, thanks. Slow to fast enough is good for my purposes. Haven’t decided what to do with the Johnson 88.
May have to study up on props. I know I’ll get comment clubbed for saying it but in the state i live in any boat with over a 50 hp engine has to be insured. Wanted a 50hp but by the time i sell the trailer and other parts I’ll have little in the engine. Everything I’ve ever owned I’ve dragged in broke and fixed so i come to liking it that way. Thanks again.

 

[roffey]

At the end of the day its what your happy with. As long as you know the risk and have all the information at hand, your good to go.

 

[Sea Rider]

Is that Evi 40 HP motor a through hub exhaust or the older non through hub exaust prop, this is very important to know. If the latter there are very few prop options to choose from, what's the stamped number on current prop if happens to have one ?

Did a prop search at Iboats :

http://boatpropellers.iboats.com/Evinrude-Outboard-Propellers/?chart=11&engine_id=43&*******=721023611

If you can find a less prop pitch to pull current wot rpm up combo will work much better than it does right now with current prop with whichever number is stamped on prop body or blade.

Happy Boating

 

[Old Ironmaker]

All great replies, thanks. Slow to fast enough is good for my purposes. Haven’t decided what to do with the Johnson 88.
May have to study up on props. I know I’ll get comment clubbed for saying it but in the state i live in any boat with over a 50 hp engine has to be insured.

I think every boat on the water should be insured for liability just like cars and trucks. I don't see the difference. An injury is an injury.

 

[Texasmark]

Is that Evi 40 HP motor a through hub exhaust or the older non through hub exaust prop, this is very important to know. If the latter there are very few prop options to choose from, what's the stamped number on current prop if happens to have one ?

Did a prop search at Iboats :

http://boatpropellers.iboats.com/Evinrude-Outboard-Propellers/?chart=11&engine_id=43&*******=721023611

If you can find a less prop pitch to pull current wot rpm up combo will work much better than it does right now with current prop with whichever number is stamped on prop body or blade.

Happy Boating

On the subject, back in the 50-70 era, aluminum props were the norm. If you wanted something other, Michigan Wheel was the source. MW is still in business and sell props to iboats. They also used to, maybe still do, have a hp to boat reference (their best at a WAG) where you can get an idea as to what an "average" rig of such and such length and such and such engine with their such and such prop will deliver in performance........if nothing else, it's a place to start.

Before you do, get a tach, even a tiny tach or for a song, you can get an electronic non-contact tach. You put a piece of reflective tape on the flywheel and the digital tach will read your rpm. Need 2 people but it will give you a starting point. Then look up your engine's recommended wide open throttle range and compare your reading to the upper end of that range. Come back with the numbers and we'll help you the rest of the way.