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Old 04-25-12, 05:37 AM   #1
Amarillo Palmira
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Default Lost Top End after Prop Recupped

I have a 200 Mercury Optimax on a 2007 Stratos 294, with a Mercury Tempest Plus Prop, 27P. I had the prop recupped at a local shop, put it back on, and my top end dropped from 74 GPS to struggling to reach 68 GPS. Hole shot is excellent, though. I took the prop back and the dude was baffled so he reset the prop back to how it brought it in. Still didn't work. I took the prop to another shop and he recupped it and burnished it a little bit for a better bite. Well, I'm still maxing out at about 68. Trying to figure out what is wrong. My prop knowledge is zero, and the best I can come up with is A. He gave me back the wrong prop and B. Somehow the engine did not adjust to the additional load from the recupped prop. Anybody have any ideas, this is maddening!! THANKS!
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Old 04-25-12, 08:08 AM   #2
bassboogieman
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Are you still turning the same RPM's with the re-worked prop? I'm guessing you are, as it wasn't mentioned you lost any. I'm certainly no expert, but if you changed the cup on the blades, you may have to tweak the motor height to get the top end back. Regardless, initially I thought turning a 27P with a 200 HP was a bit too much prop, but as it worked well prior to the prop job, I guess it's not, but I turn a 27 (3-blace) on my TR-21 with a 225 Yamaha, and although your boat is a bit shorter, the weight is about the same. I also have a 4-blade prop (26P), and a 3rd, 27P, 3-blade and they all like a little different motor height, when it comes to getting the most top end from any of them.
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Old 04-25-12, 09:51 AM   #3
lilmule
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Added cupping increases grip,reduces rpms generally but one can then raise some if its is still getting water or eq with a low water nose cone,thus getting it back the rpms and a gain in speed.If not raising cuppiing would add little or no speed gain unless prop was slipping badly,and if stock lower unit at 3 1/2 deep a very poor prop.Prop pitch isnt ordained by size of hp,its by its size and weight its pushing as some are small eared designed to get rpms up and some are large eared -thru the hub(raker) over the hub(chopper) and combos such as tro4,ot 4.
I often use old school props like Shooter it does slip at higher heights but at stock heights works ok,I have them reworked as have low water capabilities normally and run them to the pad with no problem.
Your problem most likly is not the prop,just happened to occur at same time,so logical to blame it.Water temp change warmer means less speed,windier same compare conditions,spring its fast ,summer its still fast just not as fast.Carbs,junk,mere particle in the jets,poof where went the speed.When was the last time you seafoamed it.
Im turning a 25 m on a stock 2.6 yamaha,light boat(800 lbs) could turn more easily,have hard enuff time keeping the lil bugger on the water now,have a 28 p chopper on my 150 frankenrude,commonly ran 27 p shooters on even heavy boats with 200 hp also eq with bobs nose cones and hydraulic jp.
I doubt if its prop related,since been put back and forth with little change.
One of the biggest mistakes most make with props regardless of size is they prop for wot,not optimal rpms by mfg your motor will last longer running 5300-5700.
Just goes faster at 6000,much like burning a candle at both ends
Last but not least if speed and handling dont change,your wasting your money on changing the props,they dont need added cup,if it is gripping and your bow or stern is high enough.
Im an advocate of reworking but one must gain something,if not speed, handling,and to me handling is more important than speed.I generally set mine so it runs tad less than total speed,so it handles decent.4 blade less torque but less speed,best of both worlds.
That said my allison 2002 with a 150hp will do about 80 one up,and the small 17 ft hydrosport with its 2/1 gr 65mph,and it is harder to drive.
Added cup will lower rpms about 100,if possible raise 1/2 in,1/4 at a time and gain that back ,do so only if its getting water psi your merc requires about 12 psi min,water psi gauge needed,or low water nose cone.
Or be satisfied with what it does,and take good care of it in and out.
All kinds of things will cause a few mph loss,including loss of compression starting,fuel issues ,air issues,possibly a forteller of a problem later and one should tend to it not with a prop ghuru but by a mechanic.

Last edited by lilmule; 04-25-12 at 12:36 PM.
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Old 04-25-12, 06:55 PM   #4
Amarillo Palmira
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Thanks for the replies. Great information. What happened is that I did not cup the prop for more performance, I just basically had it put back to stock after running through more than a few shallow areas that took its toll on it. It was dinged up and lost some cup, but I could still push 72-74. After it was fixed, I put it back on, but could not even reach the speed I had before it was "fixed". That's the baffling part. I did lose some RPM from about 5650 to 5400. So, I took it back to the shop and he put it back to how I brought it in (minus the dings) but I still couldn't go past 68. So, I took it to a different shop and he "recupped" it and burnished it a little. All this was done with just normal maintenance in mind. The motor height is good. It was set up perfectly when I bought it and I've never had any problems with it. It was tuned a little over a year ago, but to my knowledge, never Sea Foamed, so I put some in today. Anymore ideas? Your help is greatly appreciated.
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Old 04-25-12, 10:01 PM   #5
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A lot of people dont realize over time wear and tear thin a prop down and make it out of pitch,yes its normal maintenance most would not do,sometimes however one is just wore out or has some loss,not generally associated with a rework,just over a period of time.
Possibly another prop would get it back,dunno.
Would keep an eye on it for any more drop in speed or lack of uumph to get up and go.
Seafoam will make it smoke more when first started its not your engine its soot of the cyl walls-normal,I also use blue stable which keeps the gas from turning and has carb cleaner in it,every other tank gets it on my older motors.
As motors age they wear with additional hrs they dont do as well as when they had little hrs on them,taking care internally helps also use a good grade of oil like amsoil or what ever your engine mfg recommends like as in ficht.
I love walley world but not for my oil,you can pick up the seafoam there and the blue stable.
I have to tell you im not a merc man or a tempest man,if I did own black it would be a small hub trophy,combo over and thru.
I do own and run performance boats with omc and yammer and generally have to have mine reworked because of the elevation run at,stock props just dont work well at pad level or above.But tend to tweak mine less than most as like to be able to steer and enjoy the ride.Tend to get lengthy but hopefully some of it helped.
Currently own and operate a 77 omc x flow 140(first year of mfg),89 2.6 yamaha 150,94 franken rude box stock 150,with 24 p to 28 p props
My opinion a 25-4 blade or 26 P 3 blade trophy would make it scream try and borrow one to try it

Last edited by lilmule; 04-25-12 at 10:15 PM.
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Old 05-14-12, 06:09 PM   #6
Amarillo Palmira
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Turns out it was not the prop, but my fuel lines were eaten up by ethanol. The particularized rubber got into the VST, fuel filters, etc. and clogged everything up. After the shop cleaned all that out, replaced fuel lines and fuel filters, and performed the annual service, the boat is back to normal.
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Old 05-14-12, 08:19 PM   #7
lilmule
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UH
Your problem most likly is not the prop,just happened to occur at same time,so logical to blame it.
Glad you have it taken care of.Still think a trophy would make it fly.
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Old 05-19-12, 06:48 AM   #8
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I'm going to see about trying that Trophy. Thanks lilmule.
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Old 05-19-12, 09:38 AM   #9
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Np id still use those products will help dissolve foreign matter in the tank,larger inline filter made for marine use but the size of an auto filter will take out water and small particles prior to it getting to engine,wont take care of a rotten setup as in aged rubber but will let you know its about to happen as filter will trap some,if you check it regular.
No one thinks about boats ,hoses ,rubber buy an old car one has to put tires and all new hoses on it,boats are the same.You would be surprised at the amount of boat owners running original hoses and the boats are 15-20 years old.
Ive even drained my gas tank and cleaned it,thru the sending unit hole.Nothing like being 20 miles from nowhere and a non running engine.
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