Lost Prop

[zibzer]

So i was boating the other day and somehow my boat prop fell off my 1979 100hp Evinrude motor. Prop, nut, coter pin and all.

Now im looking for a replacement.

I had a 13 3/4*15 prop

boat ran at 5000-5200rpm at wot on a 17.5ft Peterborough Runabout and it gets 27mph.

now id like to get the motor in the 5600rpm range but id also like to get more speed out of it. Can somebody tell me what prop I should be looking at getting? thanks! im afraid if i go down in size ill lose more speed. for my setup i would guess 35mph should be easily attainable.

 

[steelespike]

Re: Lost Prop

I'm no expert but it seems to me that a 100 hp would twist a 15" pitch up
more than 5,000 rpm. And as you said 30-35 mph.You might check your compression,be sure the carb is opening all the way.Be sure the bottom is clean.Is the antivent plate even with the bottom of the boat?Is the boat an unusually heavy design or could it have absorbed water in the flotation foam?
Is the speed by GPS?

 

[zibzer]

Re: Lost Prop

I'm no expert but it seems to me that a 100 hp would twist a 15" pitch up
more than 5,000 rpm. And as you said 30-35 mph.You might check your compression,be sure the carb is opening all the way.Be sure the bottom is clean.Is the antivent plate even with the bottom of the boat?Is the boat an unusually heavy design or could it have absorbed water in the flotation foam?
Is the speed by GPS?

Havent checked compression,
carbs are opening 90degrees
bottom is clean, (it is stored off water)
has a whale tail, so the anticav plate is fine.
the inside is dry as far as i can tell, but I have never pulled up the floor to see

Tahasdaddy has stated in another post I should check compression, and link and sinc, and clean carbs

 

[papasage]

Re: Lost Prop

that is a big boat for a 100 hp . i had a 115 on a boat about that size . didn`t check the rpm`s but at WOT it would do about 30 mph . you could go to a 13 pitch would git the rpm`s up but would be longer on plain and harder to pull up skier up .my 55 hp and a 75 hp doesen`t go much faster maby 1 to 2 mph . just git on plain quicker .

 

[Dhadley]

Re: Lost Prop

That looks like an SST I. The props today will be a bit more aggressive but I still wouldn't drop pitch simply to gain rpm. Looks like the motor is fairly low, hard to tell when it's tilted like that. But it is mounted all the way down which is rarely the most optimum setting.

If that was the prop you lost and it was indeed an OMC prop then going with todays version would be the SST II. You should be able to run it higher than the earlier version. You could go with something like a Stiletto but again, I'd stay at 15" and raise the motor to improve efficiency and gain rpm.

 

[zibzer]

Re: Lost Prop

That looks like an SST I. The props today will be a bit more aggressive but I still wouldn't drop pitch simply to gain rpm. Looks like the motor is fairly low, hard to tell when it's tilted like that. But it is mounted all the way down which is rarely the most optimum setting.

If that was the prop you lost and it was indeed an OMC prop then going with todays version would be the SST II. You should be able to run it higher than the earlier version. You could go with something like a Stiletto but again, I'd stay at 15" and raise the motor to improve efficiency and gain rpm.

that sounds good. how about the Solas Amita 3 on this page 15"
Part #2411-135-15

how does this sound?

 

[zibzer]

Re: Lost Prop

That looks like an SST I. The props today will be a bit more aggressive but I still wouldn't drop pitch simply to gain rpm. Looks like the motor is fairly low, hard to tell when it's tilted like that. But it is mounted all the way down which is rarely the most optimum setting.

If that was the prop you lost and it was indeed an OMC prop then going with todays version would be the SST II. You should be able to run it higher than the earlier version. You could go with something like a Stiletto but again, I'd stay at 15" and raise the motor to improve efficiency and gain rpm.

i re-read your post, it was just an aluminum prop. no SST

I can get a Solas SS prop for about 250bucks brand new, but i think id rather save my money and pay 100 bucks for the ALuminum.. Seeing as money is tight right now

Unless someone here can persuade me that the SS is well worth it.

 

[steelespike]

Re: Lost Prop

Havent checked compression,
carbs are opening 90degrees
bottom is clean, (it is stored off water)
has a whale tail, so the anticav plate is fine.
the inside is dry as far as i can tell, but I have never pulled up the floor to see

Tahasdaddy has stated in another post I should check compression, and link and sinc, and clean carbs

Whale tail looks like it is close to being in the water at speed That wouldn't do much for speed.Also it appears the antivent plate is about even with the bottom.A good starting point but it may be possible to raise the motor more.
An inch could get 2 to 3 mph under ideal conditions.Lose the whale tail
and get trim tabs perhaps smart tabs.I'm not able to be too specific but
a stainless prop will usually improve overall performance and will fight ventilation as you raise the motor.