Top end speed gain with 40 to 70 swap?

[bralex]

I was wondering how much top end speed gain would be available with moving up to a 70hp from a 40hp Evinrude. The boat is a "93" Lowe 1600 (16'). With the 40hp, I'm getting 25 mph at 4500 rpm with a 11 3/4 x 17 prop. Thanks!

 

[evinrude70hp]

Re: Top end speed gain with 40 to 70 swap?

you will get at least a 10mph increase your almost doubling the hp and it will rip you off your seat outa the hole. what yr 70

 

[bralex]

Re: Top end speed gain with 40 to 70 swap?

Don't have one yet. Was wondering if it would even be worth looking into? The 40hp is a "91".

 

[Benny1963]

Re: Top end speed gain with 40 to 70 swap?

have a i6 ft old cajun alum had 40 mariner on it went27 on gps
swapped to 78 model 70 went to 46 on same gps

 

[evinrude70hp]

Re: Top end speed gain with 40 to 70 swap?

swap it dude you will not regret it.

 

[jddenham]

Re: Top end speed gain with 40 to 70 swap?

Is your wide open throttle only 4500RPM? I think it should be higher. Check that out as you might need a 15 pitch prop to run in the correct operating range.

Operating under heavy load at too low an RPM can damage a motor.

 

[bralex]

Re: Top end speed gain with 40 to 70 swap?

Thanks for the replies guys! I have a 15 pitch prop to test next. I've been told I may need a 13 pitch. Sounds like the swap to a 70hp would give me another 10mph? IF a new 70hp isn't on the balance sheet, what time of year and model year would offer the best bang for the buck?

 

[evinrude70hp]

Re: Top end speed gain with 40 to 70 swap?

get an 82' 70hp i love mine its bullet proof or you could get a newer one with oil injection.

 

[steelespike]

Re: Top end speed gain with 40 to 70 swap?

You won't regret the increase in hp.Keep in mind your WOT(wide open throttle) fuel use will increase from about 4 GPH(gallons per hour) to about 7 GPH.If you throttle back to the to a nice cruising speed you will save gas, possibly in the range of your 40,and your motor will be loafing.

 

[evinrude70hp]

Re: Top end speed gain with 40 to 70 swap?

there will be an increase in fuel consumption but as steelespike said back it down and u will save fuel as if u had the 40. but with the 70 at least u know u got the extra power incase you wanna go fast.

 

[bralex]

Re: Top end speed gain with 40 to 70 swap?

Thanks spike and 70hp! It seems like this boat with one mate (at least with the 40hp) will "cruise" on plane at just below WOT. In other words, it will plane at about 500 rpm below WOT. It would be nice to have a little additional throttle authority for GP. The on board fuel tank (13 gal,) should handle all but the exceptional excursion? Is parts availability a consideration on engines older than say the early 80's? Any recommendations on where or when to buy a used 70hp? Thanks!

 

[_brad_]

Re: Top end speed gain with 40 to 70 swap?

I would say you will see about a 30-40 % increase in your speed with the proper prop at 5000-5500 RPM.