Props.. Size does matter.

[Cheech]

Have had problems with the prop in that when I bought my boat 5 months ago, the prop was frozen on. The markings were also illegible so did not know what pitch it was.

I had a spare prop that came with the boat. 21 pitch

I recently bought a second hand prop. 17 pitch.

So with the 17 pitch that I wanted to try, I ended up getting the old one off by grinding it off piece by piece.

After trying the 21 and the 17, it was clear that the previous was a 19 pitch.

anyway,,, the 17 pitch is great, and does not load up the motor in certain sea conditions that the old 19 did. But the economy is really bad. I use to get about 1.3k per litre, but now down to 1k per litre. And to maintain the same normal cruising speed, I have to rev the motor a couple of hundred rpm that seems to be around that area of a lot of rpm for a small kph gain. Seems that to get the sam economy that I use to get, I will have no choice but to redice my cruise from 45kph to about 40 - 42 kph.

I thought if I get a better more suitable pitched prop then I would get better economy for similar cruise speed and also be less load on the motor (because it really did seem over propped).

The actual diamiter of the 17 is about 12mm less than the previous 19 and the 21.

So, that indicates that if the 17 was that extra bit bigger in diamiter then I will still have all the good bits that the 17 has given, but will give that extra bit of efficiency and hopefully economy.

Comments please.

Cheech

[blaze]

What diameter is the 17 cheech, is it 13 1/4" is it 115 merc cause if it is I will take it off your hands
cheers
blaze

[Cheech]

Is 13.25 17 pitch

Came off a 90 force. Mine is a 100 merc. Same size up till about 150 when they go to the larger size.

The only thing I had to do was make a new spacer as it was a bit different in the positioning of the centre.

Anyway!!! This is not the for sale section. ;D

[Cheech]

By the way, what does the 13.25 stand for? I measured the radius and the diameter and could not come up with a match in either metric or imperial.

Cheech

[Kerry]

Look on the bright size, your motor is much appreciative of now not having to continuously flog a dead horse around and around and around.

Your motor will benefit heaps [smiley=2thumbsup.gif]

:-X Now having to CUT/GRIND off a prop [smiley=stunned.gif] now I wouldn't even dare mention lack of maintenance [smiley=shocked2.gif] (would I [smiley=wiseguy.gif])

Cheers, Kerry.

[blaze]

13.25 is the diameter of prop
cheers
blaze

[Cheech]

Mention away Kerry. Don't think for a second that I was happy about it. Or that wheel in part 2 of the wheel bearing saga. But when you are stuck with it you just have to dig in and deal with it.

[Kerry]

Cheech, At least your moving forward. not backwards.

Cheers, Kerry.

[dugong]

give solas props a call and chat to them
if they can't get you proped right no one can
cheers

[Cheech]

anyway,,, the 17 pitch is great, and does not load up the motor in certain sea conditions that the old 19 did. But the economy is really bad. I use to get about 1.3k per litre, but now down to 1k per litre. And to maintain the same normal cruising speed, I have to rev the motor a couple of hundred rpm that seems to be around that area of a lot of rpm for a small kph gain. Seems that to get the sam economy that I use to get, I will have no choice but to redice my cruise from 45kph to about 40 - 42 kph.

I thought if I get a better more suitable pitched prop then I would get better economy for similar cruise speed and also be less load on the motor (because it really did seem over propped).

The actual diamiter of the 17 is about 12mm less than the previous 19 and the 21.

So, that indicates that if the 17 was that extra bit bigger in diamiter then I will still have all the good bits that the 17 has given, but will give that extra bit of efficiency and hopefully economy.

Comments please.

Cheech


Bump.

Does anyone have any coments about the same pitch but inceasing the diamiter?

[SeaSaw]

Craig,

When I first got my boat it had a 19 pitch prop on the old 2 stroke. The diameter on the prop was worn down nearly half an inch an each blade from years of churning sand on the Noosa bar :o. The prop over reved and the boat struggled to keep a low speed plane in heavy conditions (i.e lacked torque to keep it going). I replaced the prop with a new one still 19 pitch but now of full diameter. It lowered the top end revs to the right level and then had no problems holding a low speed plane .... more blade area = pushes more water = more torque ..... but only if the engine is not labouring, so it is important to not add diameter and find it will no longer rev out to the right level.

Can't help you too much with the technical theory (talk with solas for that), but that was my experience.

Cheers,

Mark