need help getting a stratos out of the hole

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rangerfscott

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Mar 13, 2011
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hello gents. i have a 2002 stratos 19xl silver star w/ 2002 mercury 200 carbureted engine. current prop is a tropy plus 4 blade 13.75x25p. current wot rpm with just me@200lbs is 5400 to 5500 top speed around 60 to 61mph per gps. if i fill up the livewells speed and rpm are dramatically affected. speed down to 54 and rpm fall off to 5200 to 5300. even with live wells empty the boat has a very hard time getting on plane and with them full it takes forever to get up. worried about the increased pressure i am putting on the motor while trying to get out of the hole. rpm will rev up to almost 4000 while it is pushing to gain lift. i raised the engine via the jackplate and it helped but i can't go anymore. when i trim out now i start loosing water pressure. now the question. does prop diameter have much effect on rpm? 13.75 vs going with 4 blade that is 14 or more in diameter. i am considering moving up to a 3 blade w/ 26 pitch. a fury prop is 14" and i think a tempest is 14.5". shouldn't i get more lift and push under a heavy load with the bigger size while keeping rpm around the 5500 mark? i know this is a lot of info but any help will be appreciated. oh also the trophy has the small barrell and i am loosing exaust because the hub is larger than the prop barrell. i know it is quite a bit because it is turning the barrell black at the base. the motor is newly rebuilt last week and i am looking for some good ideas to get a decent hole shot and decent speed without putting the engine in a strain. thanks.
 
Robbabob

Robbabob

Senior Chief Petty Officer
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Jun 5, 2009
Messages
678
Re: need help getting a stratos out of the hole

Just forgot to save my posting before sending it and now I am starting all over.. guess what, it's going to be shorter now! lol

First of all, welcome to the forum!

You have a lot of great information. Go to the top of the prop section and find the sticky to fill in the essential data requried. You have most of it within your email, just easier on us to help when it's laid out easier to read.

Also include:
if you have a SS or aluminum prop now.
what is engine rated max rpm?

The small changes in diameter are not worth fiddling with for your boat. We need to stick with material of prop, number of blades and pitch. Realize a 4-blade will give the better hold shot, but not give you the best top end.

Good luck!
 
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rangerfscott

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Mar 13, 2011
Messages
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Re: need help getting a stratos out of the hole

sorry. thought i had most of the info in here. i'll lay it out easier. 1)i would like a better hole shot without sacrificing too much speed. 2&3) currently have a merc trophy plus 4 blade ss 13.75x25p with small diameter hub(about 3 7/8"). i was told that mercury had tried a smaller hub and gearcase at one time and these props were made to fit it. don't know if that was true. 4) mercury 2002 200hp carburetor engine. max wot rated at 5600rpm. currently doing 5500 with empty livewells and just avg load. speed hovering around 60 to 61.5mph by gps. 5) boat is a stratos 19xl 2002 model. i believe it is 19' 6" and hull weight about 1650lbs. hope that helps. thanks.
 
Tail_Gunner

Tail_Gunner

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Re: need help getting a stratos out of the hole

The first thing i would do in your situation is find out where the Wot rpm is for that motor...Out boards are all over the place in suggested top rpm levels..The outboard section of the forum should be able to guide you....As to launch your boat is trying to climb over the pressure wave or on top of it and your motoring is digging in....Trim tabs would really help more than any prop is ever going to...they fight the digging action which helps the motor and prop push you out of the hole...very simple.

Watch for Dhadley posting....The guy is very well versed in such applications...
 
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rangerfscott

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Mar 13, 2011
Messages
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Re: need help getting a stratos out of the hole

the motor is rated at 5600 rpm on the tag mounted on the engine. i am getting 5500 now. i have never seen trim tabs on a bass boat hull before but there is always a first time i guess. what effect does prop diameter have on rpm? current prop is 13.75x25p 4blade ss. looking at 3 blade ss that is 14.675x25p. shouldn't the extra blade area drag rpm down enough to compensate for the loss of the one blade?
 
Tail_Gunner

Tail_Gunner

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Re: need help getting a stratos out of the hole

Well that trophy is a good prop how old is it and is there any blushed areas..that is a dull finish a bit like someone has taken steel wool to the blades

1. what is the gear ratio
2. how many gallons of water in the live wells
3. does the prop mate flush to the gear hub....a good pic maybe
4. When WH was here often he would have outboards setup for rpm ranges above the mfg ratings you might want ask in the OB section...and maybe not..;)
5. does the prop mate flush to the gear hub...pics??
6. maybe a pic of the cavitation plate in relationship to the bottom of the hull
 
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rangerfscott

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Messages
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Re: need help getting a stratos out of the hole

NO. the prop does not mate flush with the hub. it is about 3/8" smaller than the hub thereby letting exhaust flow around it and over the blades. tried a 3 blade that mated perfect. quicksilver 25p but the rpm went past 5600 and i backed off. although it did help the hole shot. cavitation plate is above the bottom of the keel with 2 more steps(pads) below that. can't go any higher. already losing water pressure at full trim and surfacing the prop some. wish i had a 4 blade that mounted flush with hub. keeping an eye out for one on ebay now.
 
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rangerfscott

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Mar 13, 2011
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Re: need help getting a stratos out of the hole

p.s. getting my daughter to take some pics of the prop mount. i am on the road right now. what effect would a larger diameter 3 blade like a tempest at 14.625" have on rpm if i am already getting 5500 out of the 4 blade trophy at 13.75". both being the same 25p?
 
Tail_Gunner

Tail_Gunner

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Re: need help getting a stratos out of the hole

rangerfscott said:
NO. the prop does not mate flush with the hub. it is about 3/8" smaller than the hub thereby letting exhaust flow around it and over the blades. tried a 3 blade that mated perfect. quicksilver 25p but the rpm went past 5600 and i backed off. although it did help the hole shot. cavitation plate is above the bottom of the keel with 2 more steps(pads) below that. can't go any higher. already losing water pressure at full trim and surfacing the prop some. wish i had a 4 blade that mounted flush with hub. keeping an eye out for one on ebay now.
Click to expand...


I hate hub size performance discussions and theory..But my experience with mismatched gear hubs and props always ends up with higher slip and lower speeds. If you stop and think about it 3/8 is a huge gap that could all kinds of unwanted turblence....and you have said as much with a 3 blade mated correctly and giving a better hole shot...The quick silver is not noted for high performance and could well explain the higher rpm and less blade area yet quicker out of the hole..

May i ask is your gear case hub 4" or 3.5"

If we had a gear ratio we could look at slip factors along with the water in the live wells....It sounds like that prop isnt hooking up
 
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rangerfscott

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Mar 13, 2011
Messages
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Re: need help getting a stratos out of the hole

lots of turbulence and slippage indeed. prop is black from all the exhaust flowing over it. gear ratio is 1:87 i believe(standard for v6 outboards 150 and up) live wells hold at least 25 gallons per and overflow tube is only about 2" from the top. so with both full that is another 400 lbs. i only use one though unless i have over 20 or 25 pound limit. but as it gets hotter i'll have to use both so i'm trying to work out these bugs before then. only had this boat 2 months. used to own a 520 ranger. wish i had it back!
 
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rangerfscott

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Joined
Mar 13, 2011
Messages
27
Re: need help getting a stratos out of the hole

here are the pics of the hub/prop mount up. notice the gap and size difference. also the cavitation plate in reelation to bottom of boat.
,
,
.hope those come thru.
 
Tail_Gunner

Tail_Gunner

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Re: need help getting a stratos out of the hole

You need a new prop. might want to take that three blade and do a wot run with gps...I once ran a a 22p laser small hub it was the same issue..it sure sounded like i was going somewhere but thats all it did...

Its hard to say where to start...but numbers from that prop are useless...

http://www.boatownersworld.com/Props/turbo/xtp.htm..... Some nice stuff there...;)

http://boatpropellers.iboats.com/Me.../7693/?**********=476850397&*******=030356925

That titan is a solid prop

By the way your running @ 13% slip.... :D I really believe that motor should or can be run at high rpm 5500 is really low for a OB....But then again i dont stick my nose in them to often
 
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rangerfscott

Cadet
Joined
Mar 13, 2011
Messages
27
Re: need help getting a stratos out of the hole

already looking. gonna query some of these guys that have a similar setup and see what pitch and prop and rpm there getting. found a great deal on a fury 26p but hate to buy it and it not work. anyway i can still fish while i look. thanks.
 
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