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18 ft Guardian Weight Issue Repower 150 Honda
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| Bigchill |
Posted on 03/09/11 - 2:29 PM
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Have repowered 1987 Model 18 Guardian with a 150hp Honda, Only Getting 3900 RPM & 34.5 MPH, Supposed to get 6000 RPM & 42 MPH, Weighed boat 4020 LBS, Included 28.5 gallons fuel = 175#, Engine 485#, 3 batteries 165#, trolling motor electric 60#. Prop 15.5 x 17 stainless. Does the boat have to much water in hull to make it overweight? Do not have owners manual showing the proper weight for 1987 18 Guardian. Or would boat still be able to hit 6000RPM overweight?
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| tedious |
Posted on 03/09/11 - 2:41 PM
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There may or may not be an issue with weight. You are certainly radically overpropped. What prop do you have on there, and how did you choose it?
Tim
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| Tom W Clark |
Posted on 03/09/11 - 2:52 PM
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How do you know the boat weighs 4020 pounds?
If it does, it is grossly overweight. I estimate a 1987 Guardian 18 (specified hull weight of 1750 pounds) with the described equipment and fuel should weigh about 2700 pounds.
Even allowing a few hundred more for equipment you may have forgotten to add, that leaves the boat half a ton overweight.
And yes, that could account for the profound loss of speed.
If you have forgotten to take into account the weight of a trailer, then it might not be so bad.
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| Bigchill |
Posted on 03/09/11 - 4:23 PM
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Misquoted weight: 4200 lbs includes trailer 920 lbs, 28.5 gallons fuel 175 lbs, 3 batteries 165 lbs, Honda 150, 485 lbs, trolling motor 60 lbs, front seat 20 lbs = Net Wgt 2200 lbs.
Boston Whaler Commercial Sales Guy told me they used a 15 x 17 alum prop for the same rig setup. I purchased a Michigan Wheel 15.5 x 17 stainless to use on this set up.
Trailer and boat were weighed at certified scales at recycling center, took off trailer hitch, then weighed trailer same way without the boat.
Edited by Tom W Clark on 03/09/11 - 4:47 PM |
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| Finnegan |
Posted on 03/09/11 - 4:37 PM
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I"ll bet that Honda 4-stroke weighs 50# more than they are telling you. All of the engine manufacturers, to differing degrees, understate the weight of these big 3-star engines.
Then you have add weight of gear oil, engine oil and prop.
One magazine actually weighed a Merc Optimax, Yamaha V-max and Evinrude E-tec, and found all to be heavier than advertized. Mercury cheated the least (15#), with Yamaha the most(about 60#) and Evinrude in the middle(about 40#). So if they are doing it with 2-strokes, you can imagine they are also doing it with 4-strokes.
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| kamie |
Posted on 03/09/11 - 4:46 PM
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Where is your engine mounted?
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| stuwl_98 |
Posted on 03/09/11 - 4:51 PM
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Cut it open! I just did mine and pulled 20 gallons of water out. I have 87 18 outrage with a 2010 merc and get 44 mph with a 14x 17 prop
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| Bigchill |
Posted on 03/09/11 - 4:57 PM
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kamie wrote:
Where is your engine mounted?
Long shaft motor raised to highest level.
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| Bigchill |
Posted on 03/09/11 - 4:58 PM
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stuwl_98 wrote:
Cut it open! I just did mine and pulled 20 gallons of water out. I have 87 18 outrage with a 2010 merc and get 44 mph with a 14x 17 prop
Where and how did you cut the hull and how long to drain 20 gallons of water?
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| Tom W Clark |
Posted on 03/09/11 - 5:01 PM
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OK, it sounds like you are 550 pound overweight.
When you say the motor is at the "highest level," do you mean you are using the lowest bolt holes on the motor?
What condition is the bottom in?
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| Tom W Clark |
Posted on 03/09/11 - 5:06 PM
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Have repowered 1987 Model 18 Guardian with a 150hp Honda, Only Getting 3900 RPM & 34.5 MPH...Prop 15.5 x 17 stainless.
OK, right there I see a problem. There is no way a motor with a 2.14:1 gear ratio (which is what the Honda BF150 uses) can spin 3900 RPM and hit 34.5 MPH with a 17" pitch prop.
Are you sure you are measuring speed in MPH and not knots? You are using a GPS aren't you?
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| Bigchill |
Posted on 03/09/11 - 5:07 PM
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Tom W Clark wrote:
OK, it sounds like you are 550 pound overweight.
When you say the motor is at the "highest level," do you mean you are using the lowest bolt holes on the motor?
What condition is the bottom in?
Right using the lowest holes and the bottom is clean with new bottom paint stored on trailer or hydrohoist.Would 550# make it not hit 6000 RPM?
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| Tom W Clark |
Posted on 03/09/11 - 5:16 PM
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4200 lbs includes trailer 920 lbs, 28.5 gallons fuel 175 lbs, 3 batteries 165 lbs, Honda 150, 485 lbs, trolling motor 60 lbs, front seat 20 lbs = Net Wgt 2200 lbs.
Wait a sec,
4200 - 920 - 175 - 165 - 485 - 60 - 20 = 2375 pounds net weight, not 2200.
That's 625 pounds overweight, and yes, that could account for the loss of speed.
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| Bigchill |
Posted on 03/09/11 - 5:19 PM
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Tom W Clark wrote:
4200 lbs includes trailer 920 lbs, 28.5 gallons fuel 175 lbs, 3 batteries 165 lbs, Honda 150, 485 lbs, trolling motor 60 lbs, front seat 20 lbs = Net Wgt 2200 lbs.
Wait a sec,
4200 - 920 - 175 - 165 - 485 - 60 - 20 = 2375 pounds net weight, not 2200.
That's 625 pounds overweight, and yes, that could account for the loss of speed.
4020 - 920 -175-165-485-60-20= 2200
Mistakenly put 4200 should be 4020.
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| Bigchill |
Posted on 03/09/11 - 5:22 PM
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BigChill wrote:
stuwl_98 wrote:
Cut it open! I just did mine and pulled 20 gallons of water out. I have 87 18 outrage with a 2010 merc and get 44 mph with a 14x 17 prop
Where and how did you cut the hull and how long to drain 20 gallons of water?
I looked at your pictures and see the extensive process envolved, no easy task.
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| Bigchill |
Posted on 03/09/11 - 5:26 PM
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Tom W Clark wrote:
Have repowered 1987 Model 18 Guardian with a 150hp Honda, Only Getting 3900 RPM & 34.5 MPH...Prop 15.5 x 17 stainless.
OK, right there I see a problem. There is no way a motor with a 2.14:1 gear ratio (which is what the Honda BF150 uses) can spin 3900 RPM and hit 34.5 MPH with a 17" pitch prop.
Are you sure you are measuring speed in MPH and not knots? You are using a GPS aren't you?
I am using GPS will double check the knts /mph, and will get back to you exact prop make & size, I have tried two different set ups, I also wondered if the mechanic set up the rpm gauge properly as he seemed to adjust it to the sound of the motor when we were on water testing, thanks.
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| Tom W Clark |
Posted on 03/09/11 - 5:29 PM
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Mistakenly put 4200 should be 4020.
4020 - 920 - 175 - 165 - 485 - 60 - 20 = 2195 pounds net weight.
OK, that is 445 pounds overweight. Not so bad.
If this boat is supposed to go 42 MPH with a 17" pitch prop then I calculate it to top out at 39 MPH with the added 445 pounds.
But this assumes it is propped correctly.
I still do not see how it could even go 34.5 MPH at only 3900 RPM with a 17" pitch prop. That is negative 17.6 percent propeller slip. Not possible.
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| Bigchill |
Posted on 03/09/11 - 5:38 PM
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Tom W Clark wrote:
Mistakenly put 4200 should be 4020.
4020 - 920 - 175 - 165 - 485 - 60 - 20 = 2195 pounds net weight.
OK, that is 445 pounds overweight. Not so bad.
If this boat is supposed to go 42 MPH with a 17" pitch prop then I calculate it to top out at 39 MPH with the added 445 pounds.
But this assumes it is propped correctly.
I still do not see how it could even go 34.5 MPH at only 3900 RPM with a 17" pitch prop. That is negative 17.6 percent propeller slip. Not possible.
Stuwl wrote that his 18 ft 87 whaler is proped with 14x17 prop and gets 44 mph. I would be happy for 40 right now shows 34.5 downwind fully trimmed 1 person.
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| Tom W Clark |
Posted on 03/09/11 - 6:00 PM
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The Outrage 18 is 500 pounds less than the Guardian 18.
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| Tom W Clark |
Posted on 03/09/11 - 6:02 PM
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Well, I note that 34.5 knots is 39.5 MPH or about what we would expect from a 445 pound overweight Guardian 18 with 150 HP on it.
Still doesn't explain the 3900 RPM.
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