'71 Evinrude Ski Twin 40 hp Prop Questions

[foxjohnc03]

I am almost ready to take my maiden voyage on my '71 Starcraft Mariner 14ft Aluminum with the '71 Ski Twin 40 on the back of it. I got the engine and boat together so I assume they were used before as a combo but am not sure. The prop that is on it now is a 10 1/2 X 13. Is this where it needs to be? I dont have a tach yet and I dont want to blow up my mint cond engine by overrevving it. Right now the engine has 150 psi on both cyls and I want to keep it that way. Until I get a tach, I will probably not exceed 3/4 throttle just to be on the safe side. Only paid $150 total for the combo and I think I got a great deal.

 

[BF]

Re: '71 Evinrude Ski Twin 40 hp Prop Questions

Hiya,<br /><br />Another poster (Paul), posted a link to a chart for 1970 johnson/evinrude models (in response to my Q about a 25 hp).. in there it lists the prop choices for the '70 40 hp as being;<br />10 3/4 x 14 x 3<br />10 3/4 x 13 1/4 x 3 <br />as well as 12p, 11p, and 8p alternatives...<br /><br />So, from that, I'd say it looks like you're around the 2nd highest pitch, and probably ball park for a lightish 14' boat... Maybe the 14 pitch would be better, but 'til you tach it you won't be sure.<br /><br />It sounds like it's been used as a set until now, so probably no harm in running as it is. If you wanna adjust the pitch slightly, you can get a prop shop to re-do your prop and add an inch worth of pitch... <br /><br />Have you done the basic's to the motor? (change gear lube, new plugs, new impeller) If you don't know the history of the motor, you won't know when any of those things have been done. Wouldn't want any surprises on your first trip out! <br /><br />I learned how to ski behind one of those motors... I like the little door for the rope start, always thought that was "fancy".<br /><br />In these parts $150 would be a steal!<br /><br />Good luck,<br /><br />Brent

 

[BF]

Re: '71 Evinrude Ski Twin 40 hp Prop Questions

Here's the link to the chart that Paul was kind enough to post....<br /><br /> 1970 johnson/evinrude spec sheet

 

[foxjohnc03]

Re: '71 Evinrude Ski Twin 40 hp Prop Questions

Thank you much, have already changed the lower unit lube and impeller. The plugs and hoses are next.