question about shaft length on a 15hp fastwin

[55evinrude]

Hey everyone! finally got my 1955 evinrude 15 fastwin running today and it runs pretty good! anyways I will be buying a new ultracraft 16' aluminum boat for it in the next week and i always thought it was a short shaft motor but when i measured just to be sure it realized it was about 18 1/2"-19" from top of transom mounting bracket to bottom of the anti- cavatiation plate.

that doesn't really work with a 15" or 20" transom so do i go with smaller or bigger? I am thinking a 20" transom because it's closer to that. you guys let me know what you think. thanks

Nathan

 

[Daviet]

Re: question about shaft length on a 15hp fastwin

Sounds like you need one with a 20" transom.

 

[55evinrude]

Re: question about shaft length on a 15hp fastwin

thats what im thinking also. but im not sure if the prop would get to much slippage than?

Nathan

 

[Daviet]

Re: question about shaft length on a 15hp fastwin

You haven't got much of a choice. When you find the boat you want ask them if you can hang the engine on the transom and check the cavation plate against the bottom of the boat, should be even or just a little above the bottom of the boat.

 

[55evinrude]

Re: question about shaft length on a 15hp fastwin

You haven't got much of a choice. When you find the boat you want ask them if you can hang the engine on the transom and check the cavation plate against the bottom of the boat, should be even or just a little above the bottom of the boat.

i like that idea, i think i will try that. thanks!!

Nathan

 

[Daviet]

Re: question about shaft length on a 15hp fastwin

Let us know how it turns out.

 

[55evinrude]

Re: question about shaft length on a 15hp fastwin

I still have to go to measure the 20" transom's on the boat im getting to see how tall they are. but i put my motor on a 15" transom (and yes it was spot on 15") on another boat i have and the motor sat way to far in the water. so I included a diagram i made.
I'm thinking 20" is the way to go, hopefully the transom on the ultracrafts are actually like 18 1/2-19" than it would be perfect.
also i noticed that the 16' aluminum that i'm getting sits very low in the water on the back and high in the front so maybe this will work to my advantage?

Nathan

 

[oldybutagoody]

Re: question about shaft length on a 15hp fastwin

That motor was designed to go on a 15" transom. It's my understanding that's about all they made back then. Long shafts were only used as pushers on sailboats.

 

[55evinrude]

Re: question about shaft length on a 15hp fastwin

ok thanks oldybutagoody! Personally i would rather have a 20" transom as I will have 2 motors and the other will be a long shaft. since the length is in the middle of 15 and 20" transom is it possible to get away with using it on a 20" transom or will i get to much prop slippage? thanks

Nathan

 

[64osby]

Re: question about shaft length on a 15hp fastwin

55 - It is a short shaft motor, to be used on a 15" transom. The water pump is just below your 15" line. The pump needs to be in water to work properly. You could raise it a little but not much

I have a '57- 10, 15 and 18hp motor, they are all the same. A 15hp will push your boat 12- 15 mph, proper trim of a newer motor doesn't really apply to the classic motors.

 

[55evinrude]

Re: question about shaft length on a 15hp fastwin

ok thanks 64osby! now im clear that i need a 15" transom. it seems like because the cavation plate is like 6" bellow the bottom of the boat it would make a lot of drag but if that's what it is suppose to be used with thats what i will use. btw nice motor man!!

Nathan

 

[Daviet]

Re: question about shaft length on a 15hp fastwin

...

 

[HighTrim]

Re: question about shaft length on a 15hp fastwin

Hey Nathan, did you use the gearcase you picked up from me?

Anyways, as stated above, you have a short shaft. The long shafts have an additional extension piece in them. It will be fine on a 15" transom.

 

[64osby]

Re: question about shaft length on a 15hp fastwin

Nathan, thanks, that one was cobbled together from a few parts motor. It looked so bad I had to paint it, but it purrs very nice.

Good luck with yours and I hope High Trim treated you right. Post some picks after you get it all set up.

 

[55evinrude]

Re: question about shaft length on a 15hp fastwin

Yes Chris I have the gearcase that I got from you on it right now. I have not lake tested it yet but I have run it in a barrel and it seems to shift pretty good!!

I got my old dinosaur running yesterday for the first time in almost 40 years! after all the work to it she runs pretty smooth, needs a bit of fine tuning here and there but overall not bad. has great compression! I'm thinking of running sea foam threw it to clean it out.

Nathan

 

[HighTrim]

Re: question about shaft length on a 15hp fastwin

Glad to hear, need any help bring it on over.

 

[55evinrude]

Re: question about shaft length on a 15hp fastwin

got it about 95% done! here's a pretty blurry pic of her and yes I know the lower unit color doesn't match, I just painted it with what i had laying around to make it look a bit better and to prevent corrosion. I will eventually re-paint the whole motor!