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Prop for 85 Predictor with 115 Merc

85Predictor

85Predictor

Member
I have already received help/input from Bakedgoods and Checkmate. THANKS!!

I figured it will be a long "wintah" in New England so I am putting this on the board.
I have about 2 3/4" from the cavitation plate to the botton of the transom. I am running a standard prop. "1972B" 13"???
Looks like almost half the blade is out of the water when at the 12 o'clock position. One blade is cracked so am looking to replace it.
Checkmate and Bakedgoods suggested going to a stainless.(Cupped) Checkmate said anything over 1" would require a cupped prop. I'm looking for some suggestions as to what prop would work well keeping in mind that I want power out of the hole for skiing. Top speed would be a side benefit, right?? Bakedgoods has great luck with a 14 1/2 x 23p.
I also have a "Doel-fin" installed.
Bakedgoods check your e-mail.
Thanks in advance!!
Have a nice wintah!!

Is the ice out yet??
 
I have already received help/input from Bakedgoods and Checkmate. THANKS!!

I figured it will be a long "wintah" in New England so I am putting this on the board.
I have about 2 3/4" from the cavitation plate to the botton of the transom. I am running a standard prop. "1972B" 13"???
Looks like almost half the blade is out of the water when at the 12 o'clock position. One blade is cracked so am looking to replace it.
Checkmate and Bakedgoods suggested going to a stainless.(Cupped) Checkmate said anything over 1" would require a cupped prop. I'm looking for some suggestions as to what prop would work well keeping in mind that I want power out of the hole for skiing. Top speed would be a side benefit, right?? Bakedgoods has great luck with a 14 1/2 x 23p.
I also have a "Doel-fin" installed.
Bakedgoods check your e-mail.
Thanks in advance!!
Have a nice wintah!!

Is the ice out yet??
 
Welcome back 85 Predictor,haven't seen any posts from you lately.I had my 85 out for about 10 minutes and ran about 44mph at 5000rpm,was wandering what you got out of your boat earlier when you had it out.I can't see any marking on the prop I have so I can't compare it with your boat.Mt 115hp engine is in the shop with what sounds like the same problem you had right after you got yours.....
 
If you were looking at putting a 141/2x23 on your boat,I don't think that would work out of the hole,don't think you could spin it up fast enough.Top end might even suffer because of the rpm loss.Played with props many years ago with my older boats,the Checkmate dealer let me borrow them to play with as long as I didn't break them.
 
GO RED SOX!!!
Just had to put that in!!
I was able to get 46 on GPS at 5500 rpm.
You can see from my post that a new prop is badly needed. Checkmate(Mike Comb's Dad) thought that I should be up around 55.
Bakedgoods gets 58. His is a 1988.
 
I have a doel-fin on my boat also and that may affect your top end,more resistance as you trim up engine.Do you know if Bakedgoods has a doel-fin and a 115hp Merc also.My boat just doesn't act like my older outboard Mates did as they were trimmed up,seemed to me they acted like you put them in passing gear......
 
Does that 2 and 3/4 inches mean the cavitation plate is that far above the bottom of the boat or that far below the bottom of the boat.I don't have mine at home to look.....
 
Just to clear thing up I instaled a "Stingray" Hydrofiol not a Dole-fin the Stingay is a one piece molded fin, unlike the Dole-fin which is a two piece and flexs out of the hole causing poor performance. I actualy lost top end when I removed it. when it is like glass on the lake I do feel a little drag from it, but when it gets choppy it comes alive!! My 16' mate runs about 5100-5300 r.p.m.'s with a 14 1/2 x 23 had a company in Algoniac, MI rework and cup the prop and I do acheive 55-58 M.P.H, Keep in mind I had my powerhead bored .015 over August 2002 so it is "special"
and remember boat stands for (BUST-OUT-A nother-Thousand)!!
bakedgoods222

Life's A Bore on Shore!!
 
Mr. Wick:
The cavitation plate is 2 3/4" above the bottom of the boat! That's why the standard prop is struggling(I think) to grab water.

Bakedgoods:
Would you say a "Dole-fin" is better than nothing? Would I cause a problem taking it off?
 
Bakedgoods was your motor a 115hp inline 6 or a v6 and what does it equate to now that bored .015 125/130hp?I have a one piece tail on my boat and when it gets running I am going to try it out with and without the tail to see how the boat reacts.......
 
To know where the prop is running the best way to measure how far below the bottom of the boat you are is like this.
1, Make sure the boat is level.
2, trim motor so it is level. 0 deg trim
3, place a streight edge on the front of the bullet on the lower unit. This is the prop shaft center line.
4, place a streight edge on the bottom of the boat at the center.
5, No measure the distance between the two.
This is how far the prop centerline is running below the boat.

I am running a 25p laser 2 @ 6300 rpm. Great hole shot, Found out you can't go wide open when the poor guy trying to get on ski's say;s hit it. Pull your arms off.
Checkmates need a bow lifting prop.
The best set up is this. The ability to run wide open. RPM is in the sweet spot. Trim is as close to 0 deg. When using trim it changes the angle of the prop shaft and the direction of forward force. More trim, you introduce downward force. Yes this will lift the bow by pushing down the stern. I run fastest at just a hint of positive trim. Hoping to cange that with the addition of set back.

GusAvatar2.jpg



1975 Checkmate Tri-mate 2, 2.4 200+ / Sky jacker 6" plate / 25p Laser 2 prop
 
I have a tall inline-6 I not really sure on the H.P. after the .015 bore I'm thinking 125 I was told by a certified Merc. Mechanic that the stock inline 6 115 put 135 h.p. to the prop and the 150 put 150 h.p. to the prop both inline 6's so it was well under-rated I still swear by the 1 piece Stingray and they now make a stingray XP some new material that reduces water friction. for $50 bucks you can't buy a better bolt on toy!!

Life's A Bore on Shore!!
 
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by 85predictor:
Mr. Wick:
The cavitation plate is 2 3/4" above the bottom of the boat! That's why the standard prop is struggling(I think) to grab water.

Bakedgoods:
Would you say a "Dole-fin" is better than nothing? Would I cause a problem taking it off?<HR></BLOCKQUOTE>
A dole-fin is better than nothing these hydro foils are designed to help take off, cut down on prop tourqe, reduce bow height etc.. I feel like I am a salesman for these types of fins but I'm just so impressed by their performance, at least on my little mate.

Life's A Bore on Shore!!
 
My 85 Predictor has a one piece fin also and it does help the boat out of the hole.I don't know what the engine height is yet as it is still in the shop but the time I did get to run it she ran 44mph at 5000rpm.Don't know prop size,could not find any markings on it anywhere.My guess would be 19 pitch but that is a guess.....
 
If your 115 Merc is an 85 in-line 6 it is probably putting out 100-110hp at the prop. 23 pitch will be too much. Best to get it turning right at the top of the rpm range, 5500-5600. I ran a 19" Ballistic on mine. I ran 50mph(gps)@5600rpm on my 16' Diplomat. Not everyone on this board are fans of Ballistic props but they turn easier than other cupped props (good for skiing), have good topend and great hold . The Predictors are known to porpoise over 45mph which should be reduced by a cupped prop.
 
Mark,
My Merc is an '87 but what you talked about should apply. I have a lead on a 14 1/2 x 21p
stainless. The aluminum I have is cracked and based on many sources(Imcluding Checkmate) is not the right prop for the installation I have.

icon_smile.gif
 
At 14 1/2" it sounds like a large hub prop. Your motor needs a small hub. Make sure it's the right hub and if you can try before you buy. Propping is a lot of trial and error since every boat, motor and prop combination produces different results. There lots of Predictors out there. What are you guys turning?
 
My motor is an 85 inline 6 115hp and I don't know what prop is on it.I ran 44mph at 5000rpm a couple weeks ago,I am going to pull the prop off tomorrow and see if I can find a part number or something that tells me what prop I have.....
 
I took my prop off this morning and found what may be a part number 90165F,does anyone know what this number equates to.I entered in in mercury express part and came back as part not found so it doesn't appear to be a mercury part.Is there a web site to look for props by number?
 
I have a 85 115 Merc on my boat,running a 21p alum. prop now seems to work well.

1979 TRIMATE 2 115 MERC.
 
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