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Max Speed VS RPM

Well I will start shopping jack plates, I found a couple of manual plates that look like they would be fairly easy to change over, its good to know people that can machine and mfg :D . I think a trip to a local prop shop is best to figure out what I need, being new to boating I have tons to learn and I don'e want to buy the wrong prop just because it looks good.
Thanks again for all of the help.
 
Still, something isn't adding up, 8% prop slip is incredibly low. I'm going to bet that tach is not accurate.[/QUOTE]
I will be looking into the tach this week.
 
NewCHKMATowner said:
Still, something isn't adding up, 8% prop slip is incredibly low. I'm going to bet that tach is not accurate.
Click to expand...
I will be looking into the tach this week.[/QUOTE]


depends on the prop and how much the manufacturer fudged the numbers. I have props that are negative slip according to their advertised pitch.
 
I have been reading about the advantages of jack plates and I found this one in the classified section here
http://checkmate-boats.com/forums/showthread.php?t=25362
Looks like a good deal, would this set back and lift help the Eluder gain anything? I have also been looking at props but I will take atc250r's advise and buy a jack plate before I spend the money on a prop. Will I need new steering cables if i put a jack plate with 5.5" of setback on the boat?
 
NewCHKMATowner said:
I have been reading about the advantages of jack plates and I found this one in the classified section here
http://checkmate-boats.com/forums/showthread.php?t=25362
Looks like a good deal, would this set back and lift help the Eluder gain anything? I have also been looking at props but I will take atc250r's advise and buy a jack plate before I spend the money on a prop. Will I need new steering cables if i put a jack plate with 5.5" of setback on the boat?
Click to expand...
You may need new cables...i lucked out with my set back.I did not need to change cable.but the rear of mine is wide open with no splash well.Thats a good plate and the price is nice also.
 
paulsboats said:
You may need new cables...i lucked out with my set back.I did not need to change cable.but the rear of mine is wide open with no splash well.Thats a good plate and the price is nice also.
Click to expand...

I will have to price cables before I make the jump to a jack plate, gotta keep momma happy so i can stay happy.:thumb: At that price it might be worth buying so I have it when I am ready.
 
Took it out after work today, water wasnt as smooth as last time, wind was 9-12 mph today, but the load was lighter. Did find some smooth water and opened it up and hit 5500 rpm's and 53 mph on GPS. As a boat noob, 53 on the water is pretty fast. It amazes me how well it rides at 50.
I do think the motor sits a little low I actually lost a little speed when I had a rooster tail.
I had a chance to look at my steering cables at work today and there is a little slack in the cables but I dont know if it is enough to add a jack plate, I will need some help with that from a pro.
 
NewCHKMATowner said:
Took it out after work today, water wasnt as smooth as last time, wind was 9-12 mph today, but the load was lighter. Did find some smooth water and opened it up and hit 5500 rpm's and 53 mph on GPS. As a boat noob, 53 on the water is pretty fast. It amazes me how well it rides at 50.
I do think the motor sits a little low I actually lost a little speed when I had a rooster tail.
I had a chance to look at my steering cables at work today and there is a little slack in the cables but I dont know if it is enough to add a jack plate, I will need some help with that from a pro.
Click to expand...
I bet it gets better the more you run it! have you looked at the sparkplugs? looking at your pics...your engine looks like its mounted in the sweet spot.if you lose speed youve trimmed up to far.
 
paulsboats said:
I bet it gets better the more you run it! have you looked at the sparkplugs? looking at your pics...your engine looks like its mounted in the sweet spot.if you lose speed youve trimmed up to far.
Click to expand...

It did seem to run and ride great at 50 and not so great when I have a rooster tail so I dont think I will be buying a jack plate. Right now at higher speeds it turns on a dime:D enough so that it scared my wife a little.
I have not looked at the plugs yet but I know I need to. There is no telling how long the boat sat before I bought it, since I bought it from a charity I did not get to talk to the original owner of the boat, but I do have his information from the titles. It has not been real cold here but it is sure a dog when you first fire it up. Takes a while to get it to start and stay running, once it is warmed up it idles like a dream.. My starter solenoid is going out:irked: the starter would disengage during start up, so I will check the plugs when i change that out. Hoping to get to it this weekend.
I want to thank every body for the advise, it has been a great help to me.
 
NewCHKMATowner said:
It did seem to run and ride great at 50 and not so great when I have a rooster tail so I dont think I will be buying a jack plate. Right now at higher speeds it turns on a dime:D enough so that it scared my wife a little.
I have not looked at the plugs yet but I know I need to. There is no telling how long the boat sat before I bought it, since I bought it from a charity I did not get to talk to the original owner of the boat, but I do have his information from the titles. It has not been real cold here but it is sure a dog when you first fire it up. Takes a while to get it to start and stay running, once it is warmed up it idles like a dream.. My starter solenoid is going out:irked: the starter would disengage during start up, so I will check the plugs when i change that out. Hoping to get to it this weekend.
I want to thank every body for the advise, it has been a great help to me.
Click to expand...
you may want to run some sea foam thru the old girl to clean the fuel system also....
 
Having a backplate would be helpful in getting the hull to "fly" better than without. If you want to experiment on a budget you can get a set of 4" set back brackets from Bob's machine for around $100 and see how the boat likes that. The rooster tail should be no higher than the top of the motor, if its higher your set up probably needs more work. The set back should make it faster without having to trim so much and it sounds like when you trim a lot it slows down. Before doing anything, see if you can get a level against the keel, adjust the tongue height of the trailer until the keel is perfectly level, then set a level on the capitation plate and adjust the power trim until that is level. Then you can use a board against the keel extending back to get an accurate propshaft location measurement. I still think that either the motor is tired or the hull is waterlogged or something is wrong with the set up. I would think that boat should be mid 60's set up and running right.
 
atc250r said:
Having a backplate would be helpful in getting the hull to "fly" better than without. If you want to experiment on a budget you can get a set of 4" set back brackets from Bob's machine for around $100 and see how the boat likes that. The rooster tail should be no higher than the top of the motor, if its higher your set up probably needs more work. The set back should make it faster without having to trim so much and it sounds like when you trim a lot it slows down. Before doing anything, see if you can get a level against the keel, adjust the tongue height of the trailer until the keel is perfectly level, then set a level on the capitation plate and adjust the power trim until that is level. Then you can use a board against the keel extending back to get an accurate propshaft location measurement. I still think that either the motor is tired or the hull is waterlogged or something is wrong with the set up. I would think that boat should be mid 60's set up and running right.
Click to expand...
At least 60 i would say.i bet plugs will help alot!
 
Now dont get me scared here, how can I tell if the boat is water logged? Both runs out I have not taken any water on. When I pull the drain plug it is dry, and the boat is not sitting to low in the water. From what i found online this engine is rated at 5200-5800 rpm, i could be looking in the wrong places? Also the engine is a 1979 and I dont jknow if it has ever been gone through, compression test done when i bought the boat were decent 109-115 i think he said, I will check emails to make sure. Using this prop calculator
http://www.go-fast.com/Prop_Slip_Calculator.htm
my theoretical top speed is 62mph @5800 rpm's, with 10% slip my actual speed should be 56mph. Keep in mind I am running the factory 21 pitch prop and I did notice it has a couple of small dings on it.
I do want to get the all that i can out of the boat for my enjoyment but most of the time it will be my wife and I on the water cruising around. Yesterday it was my wife and I when I did the speed run and looking at the # comparison the boat is pretty sensitive to weight. From 2 large people and a large kid to my wife and I and we gained 3mph.
I will try to get the boat level and measure prop height, I will also take the boat and trailer to the local scale and get a weight on it. If it is holding water I want to know so I can get it fixed.

Thanks again for all of the info
 
NewCHKMATowner said:
Now dont get me scared here, how can I tell if the boat is water logged? Both runs out I have not taken any water on. When I pull the drain plug it is dry, and the boat is not sitting to low in the water. From what i found online this engine is rated at 5200-5800 rpm, i could be looking in the wrong places? Also the engine is a 1979 and I dont jknow if it has ever been gone through, compression test done when i bought the boat were decent 109-115 i think he said, I will check emails to make sure. Using this prop calculator
http://www.go-fast.com/Prop_Slip_Calculator.htm
my theoretical top speed is 62mph @5800 rpm's, with 10% slip my actual speed should be 56mph. Keep in mind I am running the factory 21 pitch prop and I did notice it has a couple of small dings on it.
I do want to get the all that i can out of the boat for my enjoyment but most of the time it will be my wife and I on the water cruising around. Yesterday it was my wife and I when I did the speed run and looking at the # comparison the boat is pretty sensitive to weight. From 2 large people and a large kid to my wife and I and we gained 3mph.
I will try to get the boat level and measure prop height, I will also take the boat and trailer to the local scale and get a weight on it. If it is holding water I want to know so I can get it fixed.

Thanks again for all of the info
Click to expand...
Change the plugs and run it! :cheers:
 
My rationale is you should be turning that 21 to redline without a problem on that hull. If you were local I'd say I'd give you a hand checking the prop height and let you give may 22 Raker a whirl. If the boat seems that dry and it hasn't been left out in the weather uncovered I think it probably isn't waterlogged.
 
Ok I missed the beginning of this, the 79 175 is what we called the small port motorso it really shuts off around 5500, so I wouldnt run it any higher, and with a 21 at 5500 you should be going 54 to 55, which I think you are. You could use a jackplate and a raker and get yourself into the 60mph range. I have a brand new 3 " manual adjustable jackplate if you're interested and a couple 24 Rakers
 
I did hit about 5500 RPM's last time i had it out, and that was with my wife and I in the boat. If i go to a larger pitch prop will i lose getting out of the hole? Right now it seems to be a good mix. I plan on pulling the kids in a tube will i need to change props when I am pulling?
I did try to look at my plugs but I did not know the plugs are not standard size so I need to pick up a new socket this week. I bought some sea foam and a fresh can of gas mixed and ready to go in. Might take it out this week solo just to run the sea foam through it.
 
uh oh

Took the boat out after work for a little ride with the wife. We put in at a new spot and ran into some debris in the water.
20121012_205207.jpg
20121012_205155.jpg
Gonna take it to a prop shop and see if it is worth fixing. If not i will be in the market for a new prop.
Did find a couple of new scratches in the hull as well.
Lesson learned
 
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