Jack Plate height for engine - advice

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Tom Proffitt
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Jack Plate height for engine - advice

Postby Tom Proffitt » Sat Dec 09, 2006 9:55 am

I have a 2004 206 Champion with a 250 HP Yamaha with a jack plate. My problem is that the boat does not go as fast as it should. Boats with 200 and 225's blow right by me. The prop is a 25-M Yamaha prop. The jack plate has a bolt in the middle that can raise and lower the engine. The sliding part of the jack plate is about 1" above the stationary part of the jack plate. When going down the lake, there is a very large rooster tail. When testing the GPS vs. speedometer, the GPS says I'm going 54, speedometer 60. It runs at about 53 RPM full speed. I have been told to raise the jack plate higher to give me more RPM and less rooster tail. Should I try raising it higher? Any helpful advice would be appreciated to give me more speed and RPM. Professional service hasn't helped.

Thanks for your help,
Tom Proffitt

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Mike
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Re: Jack Plate height for engine - advice

Postby Mike » Sat Dec 09, 2006 10:10 am

There is some great info in here.

http://bassboatcentral.com/champion.htm

Looking through, it looks like your prop shaft needs to be about 3 1/2" below the pad. You tape a yard stick to the very botton of your boat. Let it stick out to your prop. Trim your motor down until your prop shaft it parlelle (sp?) with the stick. Adjust your jack plate until it is 3 1/2" from the center of the prop shaft to the top of the yard stick. That is a good place to start. Then go out and run it with the GPS until you find the "sweet spot" and lock it down. You should be running your trim all the way up, then just tap it down. You dont want a big rooster tail. Looks cool, but you loose speed. It should only be about the height if you motor. If that doesnt get your RPM's up, you may need to try a smaller prop. Check your book, but you should be running about 5800 RPM's.

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DanO
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Re: Jack Plate height for engine - advice

Postby DanO » Sat Dec 09, 2006 10:44 am

I don't know who's helping you, but it sounds likw you might be down a cylinder. Especially if youre only turning 5300 RPM.

I would think your prop would need to be a bigger one on a 250, more like a 27. You should be swinging more RPM's with a 25 pitch prop on a 250.


I'd have someone look a little deeper, you should be faster than 53 mph, even with an improper setup.

DanO

Rod Martin
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Re: Jack Plate height for engine - advice

Postby Rod Martin » Sat Dec 09, 2006 11:00 am

to answer your question need to know kind of jack plate, 10", 8" or what? next check your plug wires doesnt sound like your running on all 6, sometimes when installing engine cover you can loosen a wire. and your way to low on jackplate. I have a 202 champion, running a 10" jackplate, engine is bolted to plate in the bottom holes of engine mount, then my jackplate is up about 1/2 way. at 5800 I am at about 76mph GPS with a 27" 4 blade trophy, but I have a merc. 250. I drop 5mph on top end when I drop to a 6" jack gain more by going to a 12" but it puts back of boat to far down in the water. also where are you located I've had several champions set them all up myself. my 18'6" would top 70.

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Re: Jack Plate height for engine - advice

Postby JT-Madera » Sat Dec 09, 2006 11:16 am

Tom it really sounds like you have a ignition problem..I am running a 04 520VX Ranger w/ 225 Yammy I have a 25ti prop and at full throttle it turns 5800rpm's and 72.5 gps...with a short roster tail...I have a RiteHite jackplate..which is set about 2 1/2 inches high..

Best thing I can suggest is to start raising the jackplate at 1/4in at a time..watch your water pressure and trim your motor up until your water pressure starts to drop and or you get to much chine walk.. That Champion should be running circles around my Ranger..Unless you went off that diet your doctor had you on :lol: :lol: You are a big boy...I should talk huh.. :lol:

Really though, I think there is something wrong with the engine...

JT

Simon
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Re: Jack Plate height for engine - advice

Postby Simon » Sat Dec 09, 2006 12:30 pm

Check your PM.

Tom Proffitt
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Re: Jack Plate height for engine - advice

Postby Tom Proffitt » Sat Dec 09, 2006 1:14 pm

Thanks to all who replied. :D I tried the yardstick measure and it is about 3 inches below the parallel with the pad. I would have to raise the jackplate six inches to make it 3 1/2 inches parallel. Would raising the jackplate this height reduce the rooster tail? The jackplate is an 8 inch Slidemaster.

I don't believe there is anything internally wrong with the motor. It starts and runs smoothly. I've had it looked at several times (it's tuned up) and when I tell them it only runs 5300 RPM they say it is within the specs for that motor.

Hey Jim, how have you been? I've been off my diet but the boat still can get on plane.

Has anyone heard that the GPS speed is not correct? When you are measuring speed, do you trust your GPS or speedometer? I have a Lowrance 480. I've been told the GPS speed is not correct and should not rely on it.

Thanks ya all, Tom

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Re: Jack Plate height for engine - advice

Postby clayton meyer » Sat Dec 09, 2006 10:08 pm

typically a large rooster tail is an indication of the engine being too high.

The higher you get with your motor the less leverage you have. To compensate for the lost leverage you end up triming at a greater angle to create bow lift, this causes the rooster.

don't try to make too many adjustments such as changing your prop, until you have the correct height for your current combination as adjustments are free and don't raise your engine until you lose water pressure. At higher settings you start to develope steering torque that may go undetected with a hydraulic steering system. This excessive torque can add unwanted stress to the lower unit bearings.

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Jim Conlow Sr.
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There is a formula for calculating speed

Postby Jim Conlow Sr. » Sun Dec 10, 2006 4:47 pm

First of all I think you are absolutely correct about not getting enough speed
In order to calculate the potential speed you need to factor in the gear ratio from engine rpms to prop rpms. then mutiply the prop rpms time 25 inches. subtract 10 % and devide by 12 to see how many feet you are traveling in one minute. based on that number you can figure out how many miles per hour you should be theoretically traveling.
I do really think that you 250 should be able to pull a 27 inch pitch prop. I am pulling a 26" on my 225 optimax and regularly do slightly over 70 with a full fuel load and tournament tackle for two people that weigh in at around 400 together. every 100 lbs will slow you down about 2 miles an hour I have been told.
I would call phils props in Redding and ask them. By the way I have always been able to borrow props to try on my boats when I was doing a lot of experimentation

On my Legend I have bever changed a thing. It came out of the factory setup perfectly

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FRANK D. LOZANO
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Re: Jack Plate height for engine - advice

Postby FRANK D. LOZANO » Sun Dec 10, 2006 5:57 pm

Tom,
Sounds like you are down on power, Yamaha recommends 5500 RPM, but that motor will continue to make HP at 5800-6000 rpm.

Give me a ring if you can’t figure it out.

The bottom if the following page has some of set up info for you.
http://www.inland-marine.com/PROPPITCH101.html
Frank Lozano
Inland Marine Inc.
1600 West 10th Street
Antioch, CA. 94509
www.inland-marine.com

www.legendbassboats.com
www.mercurymarine.com
www.evinrude.com

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Rick G
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Re: Jack Plate height for engine - advice

Postby Rick G » Sun Dec 10, 2006 7:19 pm

Tom, here are the correct heights for a Champion/ 206/198. Put a level on the rear deck of the boat and adjust the dolly wheel untill the boat is level. Then take the same level and set it on the bottom cav. plate. Use the powertrim to level the motor. Then take a tape measurer and measure from the very bottom of the boat near the drain plug to the floor. Then measure from the floor to the Cav plate. The optimum running height should be 4 3/4"- 5" difference from the floor measurement to the cav. measurement. Example- If it is 16" from the floor to the bottom of your boat the Cav. plate should be 21" from the floor. Not real familiar with Yamaha's, but do know Champions and that is how we set up all our boats. 24p-25p large hub 3 blade should get you the most MPH. Rick G.
Anglers Marine has been serving Southern California boaters and fishermen since 1981, with the West's largest bass fishing tackle store and the best boat dealership on the west coast.
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Jay707
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Re: Jack Plate height for engine - advice

Postby Jay707 » Wed Aug 08, 2018 3:04 pm

What about for a merc 175 is it still 3 1/2 inches down from pad?


Jason

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Re: Jack Plate height for engine - advice

Postby Top'r » Wed Aug 08, 2018 4:00 pm

Jason : There are a ton of variables about setting Jackplate heights. 3 1/2 inches in simply
a " Starting " point on the setup. There is so much more to it than just 175 HP Merc. Good luck.

WRB
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Re: Jack Plate height for engine - advice

Postby WRB » Wed Aug 08, 2018 6:27 pm

Jay707 wrote:What about for a merc 175 is it still 3 1/2 inches down from pad?


Jason

Yes.
Rick G method takes the guess work out of figuring where the pop shaft CL is in refer to the pad, simple direct measurements on the level.
The OP may have some other issues, he is at least 15 mph slow and 600 rpm off and 600 rpm's doesn't = 15 mph. The entire hull must be wet and not up on the pad, could be a simple trim problem then a jack plate height issue.
A compression check should help to sort out the power issue.

Tom

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ash
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Re: Jack Plate height for engine - advice

Postby ash » Thu Aug 09, 2018 6:52 am

WRB wrote:
Jay707 wrote:What about for a merc 175 is it still 3 1/2 inches down from pad?


Jason

Yes.
Rick G method takes the guess work out of figuring where the pop shaft CL is in refer to the pad, simple direct measurements on the level.
The OP may have some other issues, he is at least 15 mph slow and 600 rpm off and 600 rpm's doesn't = 15 mph. The entire hull must be wet and not up on the pad, could be a simple trim problem then a jack plate height issue.
A compression check should help to sort out the power issue.

Tom



This post is over 12 years old, I would hope that OP has resolved his issue by now :lol:

WRB
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Re: Jack Plate height for engine - advice

Postby WRB » Thu Aug 09, 2018 7:56 am

ash wrote:
WRB wrote:
Jay707 wrote:What about for a merc 175 is it still 3 1/2 inches down from pad?


Jason

Yes.
Rick G method takes the guess work out of figuring where the pop shaft CL is in refer to the pad, simple direct measurements on the level.
The OP may have some other issues, he is at least 15 mph slow and 600 rpm off and 600 rpm's doesn't = 1d5 mph. The entire hull must be wet and not up on the pad, could be a simple trim problem then a jack plate height issue.
A compression check should help to sort out the power issue.

Tom



This post is over 12 years old, I would hope that OP has resolved his issue by now :lol:

It's only 12 years! Hate it when this happens.
Tom

Stratos278
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Re: Jack Plate height for engine - advice

Postby Stratos278 » Thu Aug 09, 2018 6:26 pm

WRB wrote:
ash wrote:
WRB wrote:Yes.
Rick G method takes the guess work out of figuring where the pop shaft CL is in refer to the pad, simple direct measurements on the level.
The OP may have some other issues, he is at least 15 mph slow and 600 rpm off and 600 rpm's doesn't = 1d5 mph. The entire hull must be wet and not up on the pad, could be a simple trim problem then a jack plate height issue.
A compression check should help to sort out the power issue.

Tom



This post is over 12 years old, I would hope that OP has resolved his issue by now :lol:

It's only 12 years! Hate it when this happens.
Tom

Better late than never... :lol: :lol: :lol:
Jim C.

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Rod Martin
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Re: Jack Plate height for engine - advice

Postby Rod Martin » Fri Aug 10, 2018 5:28 am

:lol:

I've only gone thru 3 boats since I posted on this :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:
TR177 Ranger Mercury/MK


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