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Author Topic:   25 outrage reprop-advise please
Royce posted 10-08-2003 12:10 AM ET (US)   Profile for Royce   Send Email to Royce  
I am running twin 1999 Mercury EFI 150 hp. motors on my 1985 25' Outrage Cuddy. Currently it has counterotateing Merc. Offshore 14 1/2 x 17p four blade stainless props. I am seeing 4900 rpm at WOT with a GPS speed of about 44 mph. All persons tell me that that the rpm should be much closer to Merc. max of 5600 rpm. Do any of you have experience with props on a twin set up like this? I just spent $600. to have the motors serviced and checked out by a certified Merc. mechanic. The compression in all cylinders is 120- 125 and when hooked up to the computer everything else checks out fine--its not the motors. How much rpm would be gained by going from a 4 blade 17p to a 3 blade 17p? Do I need to drop to a 15p 3 blade? Thanks for the help.
Bthom posted 10-08-2003 02:05 AM ET (US)     Profile for Bthom  Send Email to Bthom     
I can't say what the RPM will do by going from a 4 blade to a 3 blade, but for comparison's sake I run 14" x 19" counter rotating 3 blade Quicksilver stainless props on my 25' Revenge with whaler drive and 150 hp mercury Black Max's. They peak at 5500 rpm,so the extra blade on yours really makes the engines work harder.
Hope this helps.
Regards, Brian
lhg posted 10-08-2003 02:22 PM ET (US)     Profile for lhg    
I am a little confused by the data you are coming up with, considering the Mercury prop book that I'm referring to. On my 25 Outrage, with bracket mounted 1997 200 EFI's (same block and gear ratio), I can turn 21" pitch Laser II props up to 5800 with a med-heavy load, and 23" Laser II props to 5600 with a light load. Speeds are near or over 60mph.

So I would think you should be able to get 50 out of yours under ideal conditions. But your situation may not be ideal, hence a lower top speed.

Am I correct, you have a tee top? These, and other set canvas, are notorious top speed killers, as much as 3 or 4 mph, which brings you down to 46-47 or so. In looking at the Merc prop charts, 17" props on a 150 would give a top speed of 44 you are indicating, but at 5500 rpm. I do know that Mercury says the 4 blade Offshore will suffer a slight top speed loss when compared to a fast 3 blade, and that pitch-for-pitch, will run about 100 rpm slower at same speed.

Mercury's prop information,on twin 150 EFI's, is as follows:

15" pitch, load range 6400-9000#, speed range 30-38
17" pitch, load range 5400-7200#, speed range 36-45
19" pitch, load range 4800-6000#, speed range 42-49

So, by this information, and from what I have used to prop my 200's, I would say you need 19" props!! So I'm confused, like you are.

My best guesses are several.

1. For some unknown reason, the boat is heavier than we think.

2. The additional forward weight of the Cuddy is creating
more wetted surface than an Outrage would have, slowing boat. Quality (smoothness) of the bottom paint could be an issue here also.

3. The tee top is badly hurting top end & RPM. A Mills sun top could be an alternate solution.

4. The engines are mounted too low. This would be my first guess, as those four blade props are not meant to be run fully submerged, and this will hold down RPMs by effectivly increasing pitch (to more like 19") while at the same time hurting speed. I would bring them up another bolt hole, or even two, and see what you get. If they are already set high, them I am totally stumped. Currently your speed and RPM data indicate more like 19" pitch props, which makes me think engines are too low.

As I said before, I believe twin 150's on an plain Outrage 25, with no tee top or Cuddy, should get 50 mph. But on your rig, with tee top remaining, you may only be able to squeeze another 1 or 2 mph out of her, while at the same time increasing engine top RPM. I would continue to try to get those props to work, as I think they should, and are the best prop for your situation. Your only other option would be to switch to 17" Mirage Plus props, but that's an expensive risk. Faster Merc Lasers are not made below 19" pitch.

Keep us posted with your findings, and I hope some of this may be of value to you.

Sal DiMercurio posted 10-08-2003 11:02 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
I'v been working with Royce on this for a while now & i'm at a loss as to why those engines won't twist 17p props.
My guess is they should be able to handle 19p props but their only turning 4,900 rpms at wot & trimmed.
His engines are 1 hole from the highest.
The bottom is clean but somethings very wrong here.
I suggested he try a couple of 3 blade 17p Stilettos or Michigan Raptors if he can borrow them just to see if his rpms jump up much.
For some reason those engines are only able to twist 4" less pitch then they should be twisting, in order to be at the high end of the rpm range.
I'm at a total loss on this one.
Royce posted 10-09-2003 12:40 AM ET (US)     Profile for Royce  Send Email to Royce     
Brian, Larry and Sal-Thank you for your help with this anomaly. Larry- Yes I have a tee top and have recently bottom painted the boat with Micron CMC(it rolls on with an orange peel texture). I weighed the boat and trailer and then added in gear and 70 gal. of fuel (minus 1250 lbs. for the trailer)and came up with a weight of about 5600 lbs.-- plus two men at 400 lbs.-- or about 6000 lbs. I have a Raymarine Gps which gives me a speed of about 43-44 mph at 4900 rpm. Both tachs read the same and were checked by my Merc. mechanic. The 25" shaft motors are mounted on a 4.5"setback jackplate. They are 7 1/2" above the transom--I have one more hole I could move the engines up. Sal suggested that my cavitation plate should be running just out of the water at plane--it is about an inch underwater. I am very hesitant to purchase new props when all of you think that the boat is propped correctly. It looks like I had better try lifting the motors to the last hole. If any one else have something to add--I am open. Thanks again.
hauptjm posted 10-09-2003 01:57 PM ET (US)     Profile for hauptjm    
Royce, I don't mean to be sarcastic, but is it possible that the linkage is out of whack. I know you had a mechanic check out the engines and this would seem to be overly simplistic, but...

If one of the cables is out of adjustment it could be preventing you from opening up sufficient fuel supply to both motors since the cables are "coordinated" together.

Just a thought!

Sal DiMercurio posted 10-09-2003 04:58 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
I don't know why your running 25" shafts on those engines, I think theres 5" less deadrise that far out on the transom, thus 20" shafts.
Those 4 blades should be able to run with the tips of the props breaking the surface, just make sure the engines are getting enough water.
Do not mount them so high as the water intakes are not completely submerged.
lhg posted 10-10-2003 03:18 PM ET (US)     Profile for lhg    
Royce - You just gave it away, by indicating your anti-ventilation plates are 1" below the surface. That is what I thought, and is the problem. Sal's recommendation is correct, they should be just slightly above the flow coming off the hull, with the outside surfaces just about hitting the water.

By running those 17" 4 bladed props totally submerged, you have increased the "effective" pitch to 19 or 20". This perfectly explains your RMP-to-speed problem. You are also picking up too much lower unit & prop drag. The Mercury Offshore props can be run as high as 1 1/2".

Sal, although the boat was orignally designed for 20" twins, to use Counter rotation engines, any brand, you have to buy the Saltwater 25" models. It sounds to me like the bracket is problem, as it also sounds like these engines need another 2 holes of lift, which is not available.

Royce - are these brackets themselves adjustable? It sounds like they are not capable of enough lift if your engines are already in the 4th holes up. Basically, a proper bracket for your installation would provide close to the 5" of lift necessary to accomodate the 5" shaft length, and then the 5 engine bolt patterns could be used for more elevation if needed.

I know a fellow with twin 150 Optimax's (25" shafts) on his notched transom Outrage 25, and he has super heavy duty hydraulic lifts. And he also runs the 4-bladed Offshore props (don't know pitch used). He has no problem getting the engines up as high as needed. His boat runs quite well, I'd say close to 50, but does not have a Cuddy or tee top.

Royce posted 10-10-2003 10:33 PM ET (US)     Profile for Royce  Send Email to Royce     
Larry, Sal and Hauptjm -- Thanks again for your thoughtfull replies. I just measured the jack plate--I can redrill it one bolt hole higher- in doing so I will be able to effectively raise the engine two bolt holes. What is the best lifting location on a 150 Mercury? ( I do have a crane and a forklift)? And ,yes I had the merc. mechanic check the throttle linkage. Thanks again.
lhg posted 10-13-2003 04:50 PM ET (US)     Profile for lhg    
All Mercs are lifted via a lifting eye that screws into the engine flywheel, underneath the plastic cover. This lifting ring is available from your Mercury dealer. If you look at the top of the engine, you will see the large diameter threaded area.
Royce posted 10-13-2003 11:53 PM ET (US)     Profile for Royce  Send Email to Royce     
Thank You-all. I will let you know what happens.
lhg posted 10-14-2003 07:33 PM ET (US)     Profile for lhg    
One more thing - On those Mercury Offshore props, be sure you are using Mercury's recommended Medium sized vent fittings.

I know those props are shipped from the factory with solid plugs, for stern drive applications, so you may have to change them.

Royce posted 10-24-2003 12:31 AM ET (US)     Profile for Royce  Send Email to Royce     
Well, I found out that 2 inches does make a difference in the real world. I raised the motors 2 inches and took her out for a spin on a local lake today. At WOT she now reaches 5500 RPM and does 48 MPH. (one person and 1/3 tank of fuel) I have to trim it down for hole shot and then bring the motors up for efficient cruising. The motors are mounted 91/2 inches above the transom and 41/2 inches back on a jack plate. I think that I have found the sweet spot. Thank you all for your help!-
Royce posted 10-24-2003 12:38 AM ET (US)     Profile for Royce  Send Email to Royce     
Two more things. The lifting hole in the center of the Merc.flywheel is 1 1/2inch in diameter with a pitch of 16 threads to the inch. I made one on my lathe in about a half an hour. Remounting the motors took about one hour each, including redrilling the jack plate. The cavitation plate now runs just above the water level when the boat is on plane.
lhg posted 10-24-2003 01:17 PM ET (US)     Profile for lhg    
OK! Well done, Royce, and it's nice to hear that beautiful 25 of yours is now performing like it should. Actually, you're running faster than I would have thought, considering the Cuddy and Tee Top, so those 150 EFI Mercs must be pretty strong. (am I supposed to be surprised about this?) I'll bet the 20" transom Outrage looks pretty cool with those 25" engines sitting high back there on brackets.

Your numbers indicate that even with the lifting, those 17" Merc Offshore (recently Mercury changed name to "Vensura") props are giving you an effective pitch of more like 18". This is typical of the way 4-bladed props perform.

Thanks for reporting back to us.

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