Help finding right prop

[DryFlyRy]

Hi! I have an old 14 ft aluminum startcraft which I modified greatly (decks, livewell, seats etc.) adding a lot of weight. The motor is a 1971 evinrude sportwin 9.5 or 9.9 hp and I'm looking to get a little more UMF out of it. The prop on there now has quite a few nicks and dings in it. and thought maybe replacing it would give me some better performance. However I cannot for the life of me figure out the pitch etc for it to find an appropriate replacement or even if I could, if changing these prop specs when getting a new one, would give me the more "go" Im looking for. the best i could come up with is ordering the exact part from evinrude which is a little costly... also is there a way to tweak anything internally to get more hp out of it? I thought i heard that some of these 9.9's are capable of getting more hp out of them but they were build to have less hp so they would be legal on hp restiction for some lakes... any info would be great... oh yea, one more thing... would a hydro foil help at all too???

 

[steelespike]

Re: Help finding right prop

That the rub with all that modification.
First we have to establish if you have a 9.9 or 9.5.They are different animals.If its a 71 its a 9.5. A model number would help.You can't diddle with the 9.5.There are props
available for both. Take a close look at the prop for a number like 8 1/4 X 8 1/2 or perhaps a part number.Standard pitch is around 8".But yours may not be standard.A prop shop can meaqsure it for you. Does the boat plane with this prop?
does it appear to be close to planing?Has the motor good compression?

 

[DryFlyRy]

Re: Help finding right prop

It is in fact a 9.5 hp. model number 9122r. The specs from evinrude's site of the original prop are as follows:

Product Details:

Part Number: 0383315
Description: PROP,AL 8-1/4X8
Pack Qty: 1
Dimensions: 9.75 x 9.50 x 4.50 (in)
Weight: 2.00 lbs
Equivalent Parts: 0387334,0763588

As far as the boat planing... you'll have to forgive me, this is my first boat and I am very new to all the language... but I've adjusted my tilt (or trim? the angle the ob sits on the transom) and weight distribution in the boat to a point where the boat rides level... but I can not tell if it's "on plane" like skimming across the surface of the water like I see all the big boys do on tv. I actually have a small clip of me running it on youtube, but not sure if you can tell anything... http://www.youtube.com/watch?v=tla7AhkRcB0

Have no clue about the compression. would walmart carry the gauge to check?

 

[junior1113]

Re: Help finding right prop

thats on a plane

 

[DryFlyRy]

Re: Help finding right prop

ok here's some better footage of what i got going on... from the shore perspective it doesnt look like im up on plane at all.... also here are some photos of the condition of the prop... any kind of info would be super.

http://www.youtube.com/watch?v=DALE87RecbY

 

[steelespike]

Re: Help finding right prop

I fear the boat is pretty heavily loaded for its size.Therefore it will be difficult to get it up on the water.The motor appears to wind up pretty good especially considering the hp is rated at 4,500 so 5000 would be about the max.Original prop as you stated was 8 1/4" X 8".Those other demensions must be the container.??Your prop is horrible your doing well considering.
Not knowing the present rpm its scary to change pitch.I think I would drop one size.8 1/4 X 7 1/4. Considering the load especially with 2 aboard I don't think it will over rev.What ever is causing the spray along the transom needs to be changed if possible(drag) The antivent plate just above the prop even with the bottom is considered a starting point on most motors. Your gearcase may not allow. But try raising it vertically to a point just before venting(cavitation)becomes a problem.Be sure it continues to pump water.
Just add 1/4" sticks on top of the transom .Be sure the clamps have a good grip.Sticks are just to keep the motor at the selected height.
The less you drag through the water the easier to go.Boat does appear to be a little stern heavy can you move the tank forward?Don't run that horrible prop any more than you have to,Its bad for the gearcase.
Let us know how things develope.

 

[drewmitch44]

Re: Help finding right prop

in your second video it looks like you hit someone's bouy. Its right at 2:55 into the video.

And junior1113 said that its on a plane. Its not you should say its on plane not its on a plane. If its on a plane then its in the air on a airplane.

 

[DryFlyRy]

Re: Help finding right prop

Im having a hard time finding that size prop... I have come across a 8" X 7 1/14" 2 blade on iboats here: http://www.boat-props.com/Evinrude/9.5_HP_(1964-1973)_7.25-Pitch_Propellers/19/?**********=332867723&*******=197622521... An 8" x 7 1/4: at go2marine here: http://www.go2marine.com/product.do?no=95679F which is also 2 blade or they have an 8 1/2 x 8 1/2 3 blade... Bass Pro Shops has an 8 x 7 1/4 here: http://www.basspro.com/webapp/wcs/stores/servlet/Product_10151_-1_10001_37921_225011000_225000000_225011000_225-11-0?ordProd=Y&CMID=TOP_selectitems#itemDetail but it doesnt say if its a 2 or 3 blade... THEN im looking at this chart here http://www.go2marine.com/go2_structure/mfr/michiganwheel/johnson_evinrude_outboard_props.pdf and at the bottom under the recommendation for my OB it says these are all recommended for light loads... and that the current size I have is recommended for all loads BUT the recommendation for runnabouts (which I assume are heavier) is an inch HIGHER in pitch (calling for an 8 1/4 x 9)... I am all sorts of confused now...

The antivent plate just above the prop even with the bottom is considered a starting point on most motors. Your gearcase may not allow. But try raising it vertically to a point just before venting(cavitation)becomes a problem.Be sure it continues to pump water.
Just add 1/4" sticks on top of the transom .Be sure the clamps have a good grip.Sticks are just to keep the motor at the selected height.

Im not sure I understand what you are saying here... I think you mean I should raise the entire OB up with planks so the water intake hole thingy sits just below the water?? If so, dont I risk the chance of going too high and having it not take in water and over heat? I really really really dont want that to happen...

The spray is from the fish finder transducer and cant really change that... also the original plans for the layout of the boat called for the gas tank to be up further, but when things started coming together there, unfortunatly, was only room for it in one spot which was opposite side of the driver in the stern. The only weight I can get off the stern would be a 20 lb anchor...

Thanks again for your help this is much appreciated!

drewmitch44-

As long as we're pointing out people's mistakes... I took a visit to your project page and I can quote you saying "This is how i was planing on sealing everything up. Going to glass it like this the whole way back to the transom. It looks like the pieces of wook are going to support the fiberglass very well. All im trying to do here is let water drain better and not pool up in these gaps." I believe it's spelled "Wood" not "Wook"

 

[steelespike]

Re: Help finding right prop

If you can't find a 7 or 71/4 go for the 8".If there is a good prop shop in your area they ,may be able to measure and repair the present prop.They also may be able to repitch it or the new one if it appears necessary.Raising the motor is not intended to put the cooling in peril and isn't likely to before it ventilates.Water pickup is in the leading edge of the exhaust snout from the angle of the motor and the boat The motor will surely ventilate long before you risk cooling.If you could raise it that far.I think you will run out of clamp space long before you get that high.You may not notice the difference but it could be the difference between planing and not.Though I don't think it is going to truley plane.I do think the motor has done quite well to this point. Raising will assure the motor is able to deliver its all.I'm guessing the anti vent plate is probably about 2 inches below the bottom.This raising technique was very common years ago in out board racing.Your motor was probably rated for about 20 mph on a light typical boat.Your 10mph I think is reasonable under the circumstances.

 

[DryFlyRy]

Re: Help finding right prop

gotcha! thanks again for your help!

 

[DryFlyRy]

Re: Help finding right prop

I know im a wicked pain in the ***... but JUST SO IM SURE ... Is what im describing in these pictures accurate? Or am i way off base?

 

[DryFlyRy]

Re: Help finding right prop

oh and I found/ordered a 8" diameter x 7" pitch prop that will fit this morning! thanks for your help with that