Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Short or Long Shaft
Posted by markvm on 09/23/10 - 8:27 AM
#1
I have a 1972 13' Sport, and want to know if it should be fitted with a short or long shaft outboard. I am planning a re-power with a cool vintage Mercury. Can anyone help on that?
Thanks,
Mark
Posted by markvm on 09/23/10 - 9:11 AM
#3
Thanks, I have a full splashwell, blue interior, smirkless bow, and notched transom, so it sounds like I need a short shaft and my boat is from 71 or older.
Mark
Posted by Joe Kriz on 09/23/10 - 9:13 AM
#4
Yes, all notched transoms take a 15 inch shaft unless the transom is built up with some type of a bracket.
Posted by Gamalot on 09/23/10 - 2:24 PM
#5
I don't know if the 13' hulls have the same issues as the Montauks but it was fairly common back then to mount the engines all the way down and sitting on the transom sill.
Read some of the info regarding engine mounting to see if your hull and motor do better with the engine raised up a hole or two.
As long as you are changing the motor you might as well tap the collective wisdom here and mount the new vintage motor at the best height.
Gary
Posted by markvm on 09/23/10 - 3:51 PM
#6
Thanks guys,
I have just finished reading a lot of information on here about mounting heights, particularly a thread about 16' 7" hulls. I read a lot of the advantages of mounting the engine higher, and would just like to know with my 13' sport, how can I tell if my 1969 Merc 350 should be mounted all the way down (which it currently is) or up a few holes. Also when everyone is referring to up a hole or two are they taking about hole location based on the diagram I saw in articles, or based on existing transom holes versus the holes on the engine mount? Any help will be appreciated. I also wonder if there is an optimum dimension that the prop should sit below the bottom of the hull and if that should be the factor of the mounting height.
Thanks,
Mark
Posted by Joe Kriz on 09/23/10 - 4:00 PM
#7
The holes in the transom don't move.
The engine has different mounting holes to move up (or down).
Each hole on the engine bracket is spaced 3/4 of an inch apart.
If you move one hole up, you are moving the engine up 3/4 of an inch for each hole you put the bolts through.
The engine is measured by where the cavitation plate is relative to the bottom of the transom.
The cavitation plate should be anywhere from level to 1 1/2 inches above the bottom of the hull or keel.
To obtain optimum engine height (and prop) you must have a tachometer to determine the correct WOT (Wide Open Throttle) speed of your engine according to the suggested Manufacturers specifications.
Edited by Joe Kriz on 09/23/10 - 4:02 PM
Posted by CES on 09/23/10 - 5:00 PM
#8
Markvm, welcome to Whaler central.
When I first bought my 1966 13' whaler, the motor was mounted all the way down on the transom. I raised it about an inch and am very glad I did. The performance and handling greatly improved. Just because they mounted them all the way down back then doesnt mean that is the proper position for the motor.
Anyway, If I were you, I'd raise the motor an inch or so. You cavitation plate should be above the keel.