Best prop

[marvinjansen]

My 1973 Aristocraft with Mercruiser 165hp has a 14 1/2" prop with a 19 pitch. It has one slightly bent blade and it worn on the tips. I am debating whether to fix or replace it. I see some adjustable props for around $99, are they any good? Is four blades any better than 3? Suggestions?

 

[ziggy]

Re: Best prop

hi mj.
i run about the same as you. don't know the dia. 14 1/2 sounds about right though from memory. 19p for sure, alum. it's a flo torque II and i've been more than happy with it. i achieve 4200-4400 depending on the day. my hole shot is more than adequate with my normal load of gear and 2 people.

what kinda adj. prop ya got in mind for $99. got a link? no idea if they're any good. i think bond-o's got one. and likes it a lot. but he don't have a 165hp L6.

if i considered a different prop. i think i'd consider a 4 blade. more lift at the stern. better hole shot, i'd likely go 18p for my first try. maybe 17. use it when i got more than my normal load. i don't have the extra bread for a prop right now so just have the one i got. guess my spare is a 17 fan blade type. nice hole shot, noticeable worse fuel consumption. can achieve more than wot spec. 4500.. wound pretty tight.. to tight even..

i'd repair the one ya got if yer happy with it. i just ask the other day at my local dealer. $80 for an alum. rebuild.

let us know what ya decide.

edit, here's a comment on the torque shift props.. http://forums.iboats.com/showthread.php?t=177932&page=1
to bad they'r nla..

 

[marvinjansen]

Re: Best prop

Here's a link to an adjustable prop:

http://www.westmarine.com/webapp/wc...toreNum=10106&subdeptNum=10456&classNum=10457

or WM book page 612-613

looked on Iboats and couldn't find one, may not be any good.

 

[ziggy]

Re: Best prop

may not be any good.

the folks over on the prop forum may know the answer to that question...

so do you have reason to wanting to go adj.? for that prop. to me, it only looks like it's slightly ahead of a prop nut. 4 turns with the wrench, vs, remove the nut, remove the prop, replace it, put the nut back on. granted, in the water, doing that isn't that easy.

so ya got a lot of rocks around? that would seem a benefit to that prop. snap a blade off, quick R&R it.

it looks kinda like a cleaver style prop. think that's the word. i kinda though cleaver type props were associated w/ hi performance. surface piercing?

99 bucks ain't bad. i gave a c note for my used aluminum 19p.

you could buy one and let us know how it works on a nineteen? .....

sure sucks about prop choosing. ya usually gotta buy before ya try. ya sure can rack up some bread in props finding the right one... which is partly why i stay with what i got. i performs work just like i expect it to do... imho. it's the right prop for my rig.. for the way i use it..

 

[marvinjansen]

Re: Best prop

I will try to stay with a 19.
Friend gave me a Mercury outboard 14 1/2 19 but it doesn't fit.

 

[Bamaman1]

Re: Best prop

I used to run a 21 pitch prop with a Mercruiser 140 hp. I'd run the same on a 165 Mercruiser. If I was going to pull any skiers, I'd put on my 19 pitch spare prop.

 

[marvinjansen]

Re: Best prop

That's good info. How was your top speed with the 21? I really need a prop now as last time out the hub went out with the engine revving and then only pulling when at an idle. It was a long 6 miles back to the landing. May get a Pro Pulse variable pitch to try and then carry for a spare in case I have a failure again. We hit a log earlier in the day and that may have hurt the prop but it was very old anyway. I would like to replace the hub but don't want to pay as much as a new prop would cost. Is there any way to do it yourself hub replacement?

 

[ziggy]

Re: Best prop

fwiw.
my boat came with a 21p. i could barely reach wot spec. (3900-4300). trimmed out real high i could get to the bottom of spec. imho. the 21p for my boat was to much pitch. lugging the engine, which isn't good to do. so i went to the 19p... when choosing a prop, remember, it's not about how fast it'll go, it's about being in the proper rpm range for your engine.. preferably at the top end of spec with your normal load and normal trim..
edit- fwiw. my wot speed is 42mhp gps, + or - 1 mph depending on the day..

 

[marvinjansen]

Re: Best prop

My WOT was 3500 rpm and I think my prop hub may have been slipping at that rpm. I ordered a Pro Pulse adjustable prop and will try it. It may end up as my spare to carry along as it is light. I can play with the pitch from 15-21 I think.

 

[ziggy]

Re: Best prop

My WOT was 3500 rpm

that's to low, you've been lugging your engine.

I think my prop hub may have been slipping at that rpm

i don't know how that could be. if your hub slipped your engine would race wildly. no load on it because it's not spinning the prop. + no fwd motion due to no connection between the prop and the prop shaft short of any friction that's left after the spun hub. usually ya can idle fwd. with that little friction that's left..

imho, if your prop is contributing to low wot rpm, i would guess it would be because of the bent blade(s) or the loss of the tips that you describe in your first post on this thread.

what are your compression numbers?

i'm about out of spec on mine. they range from 125-150. majority of them at 130-135. i got one high one and one low one. and the spread is to wide.. compression test...

for sure let us know how that prop works for ya. i'm real interested. cool that you'll be able to try anything from 21p-15p... i'm guessing that 21 will be too much (you'll not reach wot spec of 3900-4300). and 15 will launch you like a rocket but you'll hit wot spec. before ya got wot... just a guess.. keep us updated mj..

edit.. do your tests with your normal load and normal trim. for me that's my regular on board gear + 1 cooler and two people. trim set between the 2nd and third marks going up from full down.. maybe getting close to the third mark.. my trim limit was doa when i got the boat. only thing i'm aware of on my boat that don't work proper.. not the end of the world though. just gotta be careful i don't trim to high...

 

[marvinjansen]

Re: Best prop

I like the adjustable Pro Pulse prop. Used it to ski a week ago. Have adjusted it to different pitches and have it on 18 now to ski. did break a blade when I hit ground too close to shore, my fault. Bought a new blade and installed it and working again. Do wonder if a stronger SS prop can take more groundings? Anyway, overall happy with pro pulse prop.

 

[ziggy]

Re: Best prop

thanks for the update mj. to me, 18p sounds about right for water sports with the 165hp engine. when i was a kid, same engine on a 16' tri hull and our choice of props was 17p aluminum. for slalom and pulling multiple skiers it was just right.

Bought a new blade and installed it and working again.

sounds like your reaping the benefits of having a replaceable blade prop to me. as for the ss idea. i've stayed away from it mostly because of the groove we have in the drive shaft in the lower. the one for the o ring. i've seen more than one pic of a snapped off drive shaft due to having that groove along with using a ss prop. i'm gonna stick with alum. still wouldn't be surprised if it broke though if it found a uso (underwater solid object). but at least it'd give me some hope. sounds like since ya broke a blade off, it may be a good selling point for composite when ya have the groove. the blade broke, not the drive shaft. good deal.

 

[marvinjansen]

Re: Best prop

Pro pulse prop worked great and set to p18, better for skiing. Now got ski rope in the prop and the prop spins free at high rpm, above idle. Talking to Propulse in Sweden to get fix. Have old Mercruiser prop, 19 pitch, with bad hub. Anyone ever change hub?
Also, is our vintage Mercruiser, 1973 165hp inline 6 considered an M, R?

 

[ziggy]

Re: Best prop

Anyone ever change hub?

never done that. had a prop redo them though. i assume they R&R the hub when they (prop shop) rebuilds the prop. on my flo torqueII prop, there's a plastic piece that i assume gives (breaks) when ya hit a uso. these look replaceable at the diy level, maybe. don't know about your composite prop.

Also, is our vintage Mercruiser, 1973 165hp inline 6 considered an M, R?

it's just an mc-1. looks like 1-r started in '83, by '85 it became a 1-mr, and in '86 it became alpha1..

 

[marvinjansen]

Re: Best prop

Pro Pulse props of Sweden is sending me the parts to replace parts damaged after a ski line wrapped around it. I thought it was good that they helped me determine what was wrong and am sending me the parts under warranty.