Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Horsepower question. 48 special on a 16
Posted by Anemone on 04/13/11 - 9:26 AM
#1
I know this is going to sound like a stupid question but I was wondering if anyone knows how a 48 hp will push a 16. It came on the back of the boat and I know that it is rated for up to 100hp. My debate is that I am nearing completion of the hull project and I am trying to decide whether to go ahead and put the 48 back on it because it runs well and it would save me from having to sell this one and wait around til the right 75-100 hp comes along. Then again if I go to the trouble of installing it and I can barely plane off thats gonna suck too. Anyone have any thoughts?
Posted by blacksmithdog on 04/13/11 - 10:08 AM
#2
It really depends on what you plan on doing with it. I've had a 55 on a montauk before. For cruising and fishing it did just fine. If you want to pull your 240 pound son who's a linebacker, up on a slalom ski, go for the bigger motor.
Posted by Tom W Clark on 04/13/11 - 10:10 AM
#3
Mounted and propped correctly, it should be good for 30-32 MPH.
Be sure to fill those lower bolt holes in the transom and drill new ones higher up.
Posted by Anemone on 04/13/11 - 10:38 AM
#4
Thanks guys. That is very good news. Eventually I will upgrade power but for now it is always gonna just be me, the wife, and a 4 year old heading out or fishing with a buddy. If I can cruise at 30, that is plenty enough for me. Can you elaborate on mounting it higher? It has a lip that sits on top of the transom so I just assumed that would be the proper placement. Also, how do I determine which prop pitch to go with? I have no idea what pitch is on it now.
Posted by Anemone on 04/13/11 - 11:58 AM
#6
I know that when removing the engine, I removed 4 that were 4 through bolted. That would suggest that it was mounted correctly right? Can you comment on the prop pitch?
Posted by Joe Kriz on 04/13/11 - 12:03 PM
#7
Anemone wrote:
I know that when removing the engine, I removed 4 that were 4 through bolted. That would suggest that it was mounted correctly right?
No not necessarily. Your engine could be using the Blind holes and would need drilling new lower holes before raising the engine to the proper height.
Did the 4 bolts all have nuts?
You might measure distance between the holes you have now and compare them to the drawing.
Let us know what holes you have drilled on the drawing.
Engine height comes first before prop pitch choice.
Posted by Tom W Clark on 04/13/11 - 12:07 PM
#8
I can almost guarantee you that the Johnson 48 was mounted using the blind holes, all the way down on the transom, and as such, it was way to low.
This is why I recommend you fill those two lower holes and drill two new ones according to the article Joe has linked to.
This will put four bolt holes in your transom that you can use with this motor
or any other motor in the future without every again fooling with filling and drilling new bolt holes.
Posted by Tom W Clark on 04/13/11 - 12:11 PM
#9
The current propeller will have its size and/or part number cast into it. You may have to remove it from the motor to read the numbers but they are there.
Posted by Anemone on 04/13/11 - 12:25 PM
#10
Thanks for the great information. I will measure using the drawing this evening and report back.
Posted by Tom W Clark on 04/13/11 - 12:36 PM
#11
What is the gear ratio and WOT range of your motor?
Posted by Anemone on 04/13/11 - 12:43 PM
#12
I am gonna show my ignorance here and admit that I don't even know what "WOT" means. Where would I find the gear ratio? I am sure the local Johnson dealer could tell me.
Posted by Joe Kriz on 04/13/11 - 12:46 PM
#13
WOT = Wide Open Throttle
This is in the operators manual and is recommended not to be exceeded.
Posted by DKroger on 04/13/11 - 5:33 PM
#14
If it is a 48 spl it would have WOT of 4500-5500 rpm's and a gear ratio of 2.42:1 which is the same as the 50 hp
of the same years 1987-1995 in the 2 cly. 2 strokes.
Posted by Tom W Clark on 04/13/11 - 6:17 PM
#15
So, in other words, the same gearcase as the three cylinder 70's?
Anemone -- What year is your Johnson 48 Special?
Posted by DKroger on 04/13/11 - 6:28 PM
#16
Mine is a 1987 and runs great. I don't know what year Anemone's is.
Posted by Anemone on 04/14/11 - 6:34 AM
#17
The 48 special is a 1989. I have inadvertently intertwined the same conversation in two different areas so I apolagize if this is redundent but does anyone know if a 48 of this year has a thermostat?
Edited by Anemone on 04/14/11 - 6:41 AM
Posted by djacksonrn on 04/14/11 - 6:48 AM
#18
Evinrude.com
USA
Online Store
Parts
I entered 1987 for year
48
showed this cylinder and crankcase diagram which has part #12 in the diagram listed as thermostat OMC part number 0393659
looks like it is at the base of the cylinder head.
Posted by Tom W Clark on 04/14/11 - 7:13 AM
#19
Well, according the parts diagrams of the 1989 48 Special, the gearcase is the 3-1/2" size, not the intermediate 4-1/4" size like the 70 HP model.
It does not indicate what the gear ratio of the lower unit is.
Again, if we knew what the current propeller size or part number was, we could probably figure it out from that.
Posted by Anemone on 04/14/11 - 8:25 AM
#20
I will pull the prop and get the number off of it tonight. Thanks for the help!