1984 35Hp Evinrude - shaft length

[G DANE]

I just got the correct cylinderhead on my 35Hp and the compression increased from 122 to 145 on both.<br /><br />However I gained almost no extra speed ??<br /><br />I can see the cavitation plate is 1 3/4" below water surface, when on full speed. I have to build the transom higher to raise more that 3/4 "<br /><br />Will I get more speed if I do the change ??<br /><br />Are there any other solutions, rejetting etc. ?

 

[Dhadley]

Re: 1984 35Hp Evinrude - shaft length

Speed increases will depend on your hull design and how well it responds to samll increases in torque. If you have a pad bottom or tunnel hull you will see more speed increase than if you have a deep V hull. <br /><br />Its very common for someone to spend big bucks making their motor into a larger horsepower and see very little if any increase in speed. We work with set up more than power. Yes, getting your motor up should increase speed because you are reducing drag. Instaed of building up the transom I would look at getting a small jackplate. That will give you the ability to quickly change the X deminsion as you test. It will also change the center of gravity (more bow lift) depending on the set back. <br /><br />You didnt mention what year the motor is so we cant tell you a lot about props. You also didnt mention top RPM's or speed. Its hard to calculate slip % without accurate numbers. <br /><br />Let us know!

 

[G DANE]

Re: 1984 35Hp Evinrude - shaft length

Dadley, thanks for reply.<br /><br />The motor is on a 16' Ørnvik, Swedish deep V hull.<br />Boat weighs 450 lbs alone. I have a 10x15 propeller on, and are doing around 28 mph. I dont have a tach, but will borrow one tomorrow. I also have a 10x13 propeller. Its easy to hear I dont reach max rpm, sounds more like 4500 - i will try the 10x13, but Evinrude originally advises this up to 26 mph.

 

[G DANE]

Re: 1984 35Hp Evinrude - shaft length

By the way, motor is a 1984, but got rebuild powerhead in 2000, 2 cylinder. The rebuild powerhead was unfortunately delivered with a 20Hp cylinderhead - reason for the low compression.

 

[Dhadley]

Re: 1984 35Hp Evinrude - shaft length

Good. You could try something like the Stiletto Triad or the Turbo Hot Shot props. Although when you get the jackplate the 15 may work the best as the R's come up.<br /><br />Keep us informed!

 

[rolmops]

Re: 1984 35Hp Evinrude - shaft length

Hello.<br />You should have more power.The question is how to utilize it.It will not make you run at a higher rpm unless you change your carburator.<br />Slightly bigger prop and bigger pitch may work.(A 10 3/8 x13 1/4 seems to work best for me on my '84)<br />You may want to try to set your engine at a wider angle and thereby gain reduced water resistance.Although even a deep V can get banged pretty bad at a high angle in 4 foot waves.<br />Catch me a tosk ,will you?