Formula 27PC Complete Power plant rebuild

alldodge

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Sure is a mess in the bilge, time for some major clean up
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alldodge

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Not done but looks a lot cleaner
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Transom Assembly is out
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Kind of thick isn't it
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Christmas coming sooner :D

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tpenfield

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Wow, lots of progress. Looking good. How is the moisture level in the transom wood? Sure is a good time to fix and clean things now that the engine is out.
 

alldodge

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Wow, lots of progress. Looking good.
How is the moisture level in the transom wood? Sure is a good time to fix and clean things now that the engine is out.

I'm sorry to say, don't know the moisture content, don't have a moisture meter, should look into getting one. Wood appears to be real solid using the old screw driver push and scrap test. I need to redo my installation of the extra anodes that I put in to stop my corrosion issue years ago (Thread Below).

http://forums.iboats.com/forum/boat...eed-a-better-way-to-seal-up-additional-anodes
 

HT32BSX115

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Looks like a FUN project!


I noticed that you're considering changing to a Bravo I. On a cruiser like that I am not sure you're going to get much of a top speed increase (3-5mph according to Merc) and due to the additional slip, it may not be as economical and certainly not as nice to maneuver as a Bravo III......

How many RPM do you expect out of the "new" engine? 5500 possibly?

if so, you might want to consider a 1.81 or 2.00:1 ratio.

Referring to the prop-slip calculator, http://www.go-fast.com/Prop_Slip_Calculator.htm

2.00:1, 28p props and 5500 RPM yields approx 65 MPH and with 30p props, you get approx 70 (both using a conservative 12% slip which may be high)

Using a 1.81:1 drive, you get approx the same performance with 26p props. With a 1.81:1 ratio you would approach 3000 prop RPM though..... which might result in cavatation. (Mercury Racing or other high-speed peeps might be able to tell you something about running a Bravo III at HIGH RPM........I have read that there's possibly an upper limit on how "fast" one should turn Bravo III propellers.....)
 

alldodge

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Looks like a FUN project!


I noticed that you're considering changing to a Bravo I. On a cruiser like that I am not sure you're going to get much of a top speed increase (3-5mph according to Merc) and due to the additional slip, it may not be as economical and certainly not as nice to maneuver as a Bravo III......

How many RPM do you expect out of the "new" engine? 5500 possibly?

if so, you might want to consider a 1.81 or 2.00:1 ratio.

Referring to the prop-slip calculator, http://www.go-fast.com/Prop_Slip_Calculator.htm

2.00:1, 28p props and 5500 RPM yields approx 65 MPH and with 30p props, you get approx 70 (both using a conservative 12% slip which may be high)

Using a 1.81:1 drive, you get approx the same performance with 26p props. With a 1.81:1 ratio you would approach 3000 prop RPM though..... which might result in cavatation. (Mercury Racing or other high-speed peeps might be able to tell you something about running a Bravo III at HIGH RPM........I have read that there's possibly an upper limit on how "fast" one should turn Bravo III propellers.....)

Only reason to of even thinking of the B1 originally was that the engine will be in the 600 Ftlb of torque, estimating 525 to 575HP. From what Eddie Young tells me the B3 XR drive is a B1 XR upper but the lower is the standard B3. Merc says the B3 is good up to 525HP. Eddie is not to worried with breaking the B3 because I shouldn't be going airborne :) in my cruiser.

Plan to stick with the B3 just trying to decide which ratio, a 1.81 or 1.50 would be best bet of being able to reuse my current props (20, 22 and 24). Engine should be able to turn some above 5200, maybe 5500 but for this heavy cruiser it isn't that necessary for me. Not looking for increased speed as much as getting it up. Eddie will be balancing the engine and changing it to a MEFI-4 computer. My top end now is running the 24's at 5200. I don't see any way my cruiser has a chance to get much above 50mph, it's just to heavy. If it hit 55 I would be very impressed. I'm thinking as the boat get closer to 50 there was be more prop slip starting due to weight, just guessing.

I haven't been able to find anything on max prop rpm of the drive online. At OSO found some guys turning 6000 rpm with a 1.5 ratio drive and have been doing it for a long time. Just called Merc tech support this AM and he says there is no limit for the prop of a B1 or B3. They have found no issues with cavitation and prop rpm. With that I was thinking of the 1.81 but may want to go with the 1.50, still trying to decide.
 

alldodge

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HT32BSX115

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Just called Merc tech support this AM and he says there is no limit for the prop of a B1 or B3. They have found no issues with cavitation and prop rpm. With that I was thinking of the 1.81 but may want to go with the 1.50, still trying to decide.
I'm glad you did talk to them. I have been hearing this for some time but we hear a LOT of stuff on the internet don't we? Mercury will have experimental data that we can rely on....

As far as ratio, the same rule should apply with respect to WOT RPM and where the engine is "cammed' to produce max torque. Your engine builder should be able to tell you where that build produces max torque and the upper RPM limit. That will give you a WOT RPM to shoot for.

Once you know where you should max out, using the prop-pitch (and ratio) that gives that (@WOT) should give you "good" holeshot.

You should have previous engine performance to go on with all the different props and whatever ratio you have now (1.81, 2.00:1 or 2.20:1?)

I would lean to the 1.81:1 over the 1.5:1 in a big boat like that.......

but having said that, using 5200 rpm, a 1.81:1 with 24p props is approx equivalent to a 1.50:1 running 20p props..... using http://www.go-fast.com/Prop_Slip_Calculator.htm

My top end now is running the 24's at 5200. I don't see any way my cruiser has a chance to get much above 50mph, it's just to heavy. If it hit 55 I would be very impressed. I'm thinking as the boat get closer to 50 there was be more prop slip starting due to weight, just guessing.
What is your drive ratio now?
 
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tpenfield

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Hey Ted , found some soft wood on the transom down low. Starting a new thread in the restoration section. Going to have to cut into her and see what I find.

http://forums.iboats.com/forum/boat...hull-repair/8846856-formula-27pc-transom-work

Ouch. I hope it is not too bad. You can get a direct contact moisture meter at the big box stores for around $35. That may help in determining how much moisture the transom may have, versus buying the $400 marine moisture meter.

I'll check out your other thread as well.
 

HT32BSX115

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Ouch. I hope it is not too bad. You can get a direct contact moisture meter at the big box stores for around $35. That may help in determining how much moisture the transom may have, versus buying the $400 marine moisture meter.

I'll check out your other thread as well.
HowdyTed!, how similar are the "PC" hulls to the "SS" hulls?
 

tpenfield

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HowdyTed!, how similar are the "PC" hulls to the "SS" hulls?

Pretty much the same . . . for the PC lines and the 330SS and smaller.

Fiberglass over wood, with ribs every 18" or so along the hull. They use "Perma Panel" now and have been doing that for about the past 10 years or so. AD's and My boats are of the pre- "perma-panel" vintage.

The Fastech Line and the 370SS & 400SS hulls are the synthetic stringer system. Still wood in the transom.
 

alldodge

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You should have previous engine performance to go on with all the different props and whatever ratio you have now (1.81, 2.00:1 or 2.20:1?)

I would lean to the 1.81:1 over the 1.5:1 in a big boat like that.......

but having said that, using 5200 rpm, a 1.81:1 with 24p props is approx equivalent to a 1.50:1 running 20p props..... using http://www.go-fast.com/Prop_Slip_Calculator.htm

What is your drive ratio now?

Ratio now is 2.0 and I get around 45 to 47 on a good day (light fuel and low wind) if I remember correctly

I kind of shooting in the dark, figure current WOT with 24 pitch and 5200 rpm. If I add another 150 HP I'll over rev using the 2.0 ratio. So I'm leaning toward the 1.81 but maybe the 1.50 would give me more room to be able to use some of my current prop sets
 

alldodge

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Ouch. I hope it is not too bad. You can get a direct contact moisture meter at the big box stores for around $35. That may help in determining how much moisture the transom may have, versus buying the $400 marine moisture meter.

I'll check out your other thread as well.

Good to know, thanks
 

HT32BSX115

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Ratio now is 2.0 and I get around 45 to 47 on a good day (light fuel and low wind) if I remember correctly

I kind of shooting in the dark, figure current WOT with 24 pitch and 5200 rpm. If I add another 150 HP I'll over rev using the 2.0 ratio. So I'm leaning toward the 1.81 but maybe the 1.50 would give me more room to be able to use some of my current prop sets

It's sort of the other way around......The 1.81 might give you more "room". If you MAX out at around 5000 RPM with the 1.5:1 + 20p props, going up in pitch will only lower your max RPM.

If you exceed MAX RPM with a 1.81:1 drive using the 20's, you can go to 22's or 24's or even 26's.......The 2003 Formula 370ss I looked at had 26p prop sets on it with stock MPI 496's, and I think I remember seeing 1.81:1 drives on it......(I could be wrong about that)

Do you know where your rev limiter is going to be set (or will there be a rev-limit?)

Ted, what ratio and props do you have on your 330?
 

alldodge

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It's sort of the other way around......The 1.81 might give you more "room". If you MAX out at around 5000 RPM with the 1.5:1 + 20p props, going up in pitch will only lower your max RPM.

I would say yes/no. I started with a 330HP 454 turning the 20 pitch props and WOT at 4800. Put in the 502 (about 415hp) and went to 24 to get it to 5200. If I kept the same ratio figured I would have to go up to 30 degree props to keep from over rev. So with the new rebuild I'll have more hp but at least the same WOT rpm, maybe more but I would say not count on it. The torque usually starts falling off on the top end of the rpm. So if we figure the same WOT rpm and get the ration right, it I get more rpm it could only be a help
 

HT32BSX115

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You're going to have a lot of excess power. I would probably do a 1.81:1 drive. But since you already have 20p props to play with, a 1.5:1 drive might work. (the B-III is available in 1.5?)
 

alldodge

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tpenfield

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It's sort of the other way around......The 1.81 might give you more "room". If you MAX out at around 5000 RPM with the 1.5:1 + 20p props, going up in pitch will only lower your max RPM.

If you exceed MAX RPM with a 1.81:1 drive using the 20's, you can go to 22's or 24's or even 26's.......The 2003 Formula 370ss I looked at had 26p prop sets on it with stock MPI 496's, and I think I remember seeing 1.81:1 drives on it......(I could be wrong about that)

Do you know where your rev limiter is going to be set (or will there be a rev-limit?)

Ted, what ratio and props do you have on your 330?

I have 1.81 ratio and 26P prop sets on my 330SS. Different ballgame single engine versus dual engine though. I would think a single engine setup is going to be more sensitive to the right matchup of ratio and pitch.
 

HT32BSX115

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I have 1.81 ratio and 26P prop sets on my 330SS. Different ballgame single engine versus dual engine though. I would think a single engine setup is going to be more sensitive to the right matchup of ratio and pitch.

Same here. 1.81:1, single 7.4L Mercruiser Bravo III and 26p Props. I get 4600RPM or so at WOT (approx 56 MPH)

21' Four Winns Liberator, total weight approx 4500-5000 lbs
 

alldodge

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Same here. 1.81:1, single 7.4L Mercruiser Bravo III and 26p Props. I get 4600RPM or so at WOT (approx 56 MPH)

21' Four Winns Liberator, total weight approx 4500-5000 lbs

My Rinker cuddy has a single 7.4L Bravo 1 at 1.50 ratio, weights 4800 dry and will hit 60 with a 21 pitch 4800 rpm
 
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