Thread subject: Whaler Central - Boston Whaler Boat Information and Photos :: Mounting and Prop for Tohatsu 40 H.P. on 13 ft Whaler?

Posted by Geo on 08/12/12 - 1:54 AM
#1

I just purchased a short-shaft 40 h.p. Tohatsu TLDI 2-stroke for my 13 ft sport model 1969 Whaler. The motor weighs in at about 208 lbs and the transom is notched. Might someone have info regarding whether to mount the motor one or more holes up? Also, which prop to use? Tohatsu provides 3-blade aluminum props with 13, 14, or 15 inch pitch. Thanks.

Edited by Geo on 08/12/12 - 2:06 AM

Posted by tedious on 08/12/12 - 7:55 AM
#2

Dunno what your dealer gets for an aluminum prop, but you can get a nice Stiletto Triad II stainless prop, including the hubkit, for just a bit more than $200. With what you spent on your new motor, why handicap it with a cheapo prop?

Tim

Posted by SamD on 08/14/12 - 1:04 PM
#3

Regarding the height of the engine, I dont know which hole, however, I have a 13' with a mercury 40, i initially had the engine too low. Its a heavy engine, 216lb and everyone said the anti ventilation plate should be level with the base of the hull.

I moved the engine up and got an extra 4mph when it was level with the hull, however due to the weight of the engine and the way the boat rides i am thinking of moving it up a little more as it makes a massive difference to the performance.

Posted by Blake Whitney on 08/14/12 - 2:18 PM
#4

No answers but that is the motor I would choose if I repowered my 1969. Please report in how the setup performs and if a fancy SS prop makes a big dif!

Someday my trusty little Evinrude 30 will die!

[Moderator edit- Please don't use abbreviations or slang for engine names. Thanks]

Edited by Phil T on 08/14/12 - 3:02 PM

Posted by Geo on 08/14/12 - 4:26 PM
#5

It is difficult to find advice on this web site concerning how high to mount a 2012 short-shaft 2-stroke 40 h.p. on a 13 ft 4 inch Whaler from the 1960's. This would make an interesting topic of discussion, so I hope there is some advice out there concerning how to set up a modern 2-stroke on these older Whalers.

Also, I'd like to hear back concerning which pitch prop to use on these 2012 TLDI Tohatsu motors. I'm assuming it will be 13 inch for the 40 h.p. and I will get back on here once I have tested the motor.

An interesting aspect of these motors is that there is a kit with 2 replacement parts that will convert the motor to a 50 h.p. Given the modest weight of these motors, they seem to satisfy the urgent need to find a suitable 40 or 50 h.p. to mount on a short-shaft Whaler's transom. I would guess that a 50 h.p. will need a 15 pitch prop. Still, it is not clear how high to mount the motor?

Edited by Tom W Clark on 08/14/12 - 4:41 PM

Posted by Tom W Clark on 08/14/12 - 4:43 PM
#6

I suggest you mount the motor so the anti-ventilation plate is above the bottom of the hull.

What propeller pitch you need will depend on what the gear ratio and recommended WOT engine speed operating range is. Perhaps you could provide that vital information.

Posted by Geo on 08/14/12 - 5:22 PM
#7

Tom,

The gear ratio is 1.85.1

The WOT r.p.m. range is 5,150 - 5,850.

The motor specifications are here:

http://www.tohatsu.com/outboards/40tl..._spec.html

Edited by Tom W Clark on 08/14/12 - 6:07 PM

Posted by tedious on 08/14/12 - 5:51 PM
#8

That's interesting about the 50 horse conversion kit. How does the cost of the kit compare to the difference in price between the 40 and 50?

If you go with a modern stainless prop (and I'd certainly recommend it) then you may want to start with the AV plate 1 to 1.5 inches above the keel and go up or down from there.

Tim

Posted by Tom W Clark on 08/14/12 - 6:11 PM
#9

OK, so if we think the boat should be ale to go 36-38 MPH you would probably want a 13" pitch aluminum or a 12" pitch Stiletto Triad or Star.

There's no way you'll make use of a 14" or 15" pitch prop.

Posted by Phil T on 08/14/12 - 9:45 PM
#10

Geo -

Prior to posting did you use the search feature first?

There are:
297 posts containing the words "mounting height"
39 posts with "Engine height sport"
44 posts with "mount 40hp"

I think if you read some of them you would see the general guidelines. I strongly disagree that it is "difficult to find advice concerning how high to mount...."




Posted by Geo on 08/15/12 - 4:33 AM
#11

tedious wrote:
That's interesting about the 50 horse conversion kit. How does the cost of the kit compare to the difference in price between the 40 and 50?

If you go with a modern stainless prop (and I'd certainly recommend it) then you may want to start with the AV plate 1 to 1.5 inches above the keel and go up or down from there.

Tim


The 50 h.p. conversion kit will run you about $1,079 from Internetoutboards.com. A bit more than having ordered the 50 to begin with.

This is the web page for the kit:

http://www.internetoutboards.com/PartDetail.asp?id=1049

Posted by Geo on 08/15/12 - 4:47 AM
#12

Phil T wrote:
Geo -

Prior to posting did you use the search feature first?

There are:
297 posts containing the words "mounting height"
39 posts with "Engine height sport"
44 posts with "mount 40hp"

I think if you read some of them you would see the general guidelines. I strongly disagree that it is "difficult to find advice concerning how high to mount...."





Phil,

I am referring specifically to the mounting of a short-shaft 40 2-stroke on a 1960's Sport model 13 ft 4 in Whaler with the notched transom. I have run the various searches you have suggested, and I have not been able to find a discussion of the appropriate engine height for this configuration. If you see a discussion along these lines, please let me know.

I'm going to mount the motor 1 hole up to start with and I'll be testing it with the 13 in aluminum prop. Eventually, I might go with a stainless prop and raise the motor a bit more to see what happens. In the past, I had my Yamaha 50 2-stroke mounted all the way down and it performed well, so I'm not sure what to expect with the new motor installed a little higher up. The Yamaha weighed about 25 lbs less than the new 40 hp Tohatsu, so I expect some more bow lift with the 40 hp.

Geo

Posted by SamD on 08/15/12 - 6:30 AM
#13

Tom W Clark wrote:
I suggest you mount the motor so the anti-ventilation plate is above the bottom of the hull.


I think regardless of the hole or mounting the real issue is as stated above, the anti ventilation plate should be just above the base of the hull, so whatever hole that happens to be, use that one.