Evinrude 90hp RPM problem

[sportcraft17]

Hi there, I have an Evinrude 1986 90hp running at 5000 rpm, propeller size: 13 ¼ X 17. Boat is a 1986 sportcraft 17 feet center console. I would like to have this motor running at 5700-5800 what I have to do to increase rpm on this motor? Should I decrease pitch or increase pitch on the propeller? Any idea what propeller will work fine with this set? Boat is really heavy. Any help I will really appreciated.<br />Thank you

 

[cvx35]

Re: Evinrude 90hp RPM problem

Hi, you might want to go down to a 15 pitch for higher rpm, but i wouldn't suggest letting rpm's get over 5500. I believe that is the top recommended range.

 

[Dhadley]

Re: Evinrude 90hp RPM problem

What brand/style prop do you have? <br /><br />If the motor is mounted all the way down have you tried raising the motor any? To get to your target rpms (good choice)you may have to drop in pitch. Hopefully we can gain them with set up.<br /><br />Good luck!

 

[sportcraft17]

Re: Evinrude 90hp RPM problem

Thanks for your quick respond.<br /><br />If I go down on pitch to 15, what should I look for 13 1/4 X 15? Motor is not mounted all the way down. I don’t think I can raise the motor any higher. Is 5500 rpm the minimum rpm requires or the max rpm require by omc? Also if I go down on pitch is that going to make any difference on how long the boat will take to go on plane?<br />Thanks

 

[Dhadley]

Re: Evinrude 90hp RPM problem

Going down in pitch (reducing the bite) will allow you to get on plane quicker (engine revs quicker) but generally you will lose some top speed although it might only be slight.<br /><br />Different prop manufacturers play with diameter in different ways. Even the old OMC props, in some styles, used to go down in diameter as they went up in pitch. Today it seems everybody is looking for larger diameter. Large diameters allow a higher X dimension or higher engine mounting height.<br /><br />We find that 2 stroke motors live longer when set up in the upper 5000 range. Lugging a 2 stroke outboard does bad things to them.

 

[sportcraft17]

Re: Evinrude 90hp RPM problem

I’m using an omc part# 382764 Aluminum, 3 blades, Thru Hub Exhaust 13 1/4 X 17. What would you recommend 13 ¼ X 15 or 13 3/4 x 15? I really need to get on plane quicker I always use this boat to go fishing on the ocean and when I get 3-4 foot wave it is hard for the boat to get on plane sometimes and I need that power to get in top of the wave and stay with that wave when I’m coming back from the ocean, Speed I don’t really care if is not that much, right now I’m doing 32MPH by GPS, if I do 29-30mph I will be happy with that.<br />Thank you

 

[Dhadley]

Re: Evinrude 90hp RPM problem

I like the larger diameter so the motor can be raised. If your motor cannot be raised, I wouldn't worry about that too much. <br /><br />Just hook up with a prop shop or performance center that will assist you and let the boat be tested with whatever prop you choose before you buy it.

 

[sportcraft17]

Re: Evinrude 90hp RPM problem

Just search for a propeller and local they want $140.00 for the propeller, I’m not really sure if I can exchange the propeller after I tested out, so I have to make my mind before I’ll buy the propeller, they also told me 16 pitch will also work, what do you guys think about 16 pitch? How about stainless steal 13 ¼ X 15 vs. Aluminum 13 ¼ X 15 witch one is better? Any help I will really appreciated.<br />Thank you

 

[Cricket Too]

Re: Evinrude 90hp RPM problem

Sportcraft....I would go with the 15" pitch, the closer to 6000 RPM the better, for 2 strokes, I wouldn't be happy with 5500. I don't think there is much performance difference between aluminum and SS but stainless is much more durable, I use stainless and every now and then if I hit in shallow water, it doesn't do anything to the prop, aluminum gets beat up faster, but their cheaper.

 

[sportcraft17]

Re: Evinrude 90hp RPM problem

is there any difference bettween 13 1/4 X 15 and 13 X 15?

 

[sportcraft17]

Re: Evinrude 90hp RPM problem

any idea????