Installing short foot on a tall transom

[igotit]

A good customers boat has been down for about a year,his 40 force took a dump as expected it would.
So he bought a 97 40 merc short foot......thinking the powerhead would drop onto the ol force long foot.
But it wont.
I didnt wanna cut a perfectly good transom for a customer.
So i used 4 peices of 3"x3/8x14 aluminium angle,2-6x10 x1/4 aluminium plate and some 1/2 and 7/16 bolts.
This is my first attempt,wish i woulda used 4 in angle instead.
I set it up to use existing bolt patern the motor has.
So no additional holes in transom are required.
Gonna tidy it up a bit more tomorrow.
And while i had the motor off i added a trim unit from a 40 mariner magnum.parted with the oil injection aswell.
4" angle woulda allowed full stroke of the trim unit,as it sits the motor is 7" back from the transom and contacts the transom trimmed all the way up.
So i lose 1" of trim height.
4" angle woulda pushed my setback to 8.5-9".
But im happy.....my customer is happy.
He only has $1000 invested in the motor,parts and my fee.

http://i1141.photobucket.com/albums/n591/seven_sixtyeight/2ADD1414-26F3-4F43-8516-
5858799D3FAB_zpsyj9r8of0.jpg

 

[fhhuber]

Kind of expect that jack plate set to act as a water scoop and throw water up at the engine when on plane. A metal "pan" that closes off the opening between transom and the part the engine is bolted to would be a good idea.

Kind of make it into an open top box instead of a rectangular pipe.

 

[igotit]

Thats already in the works .

 

[fishin98]

Nice looking mount. I had a 40 Merc just like that, Great motor! Your customer will find out that the motor is a 100% improvement over the CRAPPY Force motors. The oil injection system on those motors were uber reliable VS the earlier remote oil tank models. I suggest a 11 or 12 P prop. The carbs on those engines are not tolerant of fuel being left in them for long unused periods.

 

[igotit]

The 4 cyl 40's were the best 40's in my opinion.
Its a 50 powerhead built by yamaha with 40 carbs.

 

[fishin98]

The 4 cyl 40's were the best 40's in my opinion.
Its a 50 powerhead built by yamaha with 40 carbs.

Besides they have the MODERN powerpacks on them VS the 80's power pack

 

[Guest]

Why didn't you just purchase a 5" shaft extension kit for the Merc?

 

[jimmbo]

The 4 cyl 40's were the best 40's in my opinion.
Its a 50 powerhead built by yamaha with 40 carbs.

The 1997 4 cylinder 40 is the 44 cubic in block was introduced as a 40 in 1958, was increased to 50hp in 1961 where it remained until the late 1980s where it became a prop rated 45 then 40hp. Mercury, not yammy

Being set back away from transom. you probably can raise the engine up about 1/12 - 2 inches higher than when on the transom

 

[igotit]

Why didn't you just purchase a 5" shaft extension kit for the Merc?

Why buy?
I have a long shaft 40 mariner magnum for parts.
The customer didnt wanna swap mid sections,or buy extension kit.
He insidted on a drop bracket.
I personally woulda swapped parts and convert to long foot.
But not my money.

 

[igotit]

The 1997 4 cylinder 40 is the 44 cubic in block was introduced as a 40 in 1958, was increased to 50hp in 1961 where it remained until the late 1980s where it became a prop rated 45 then 40hp. Mercury, not yammy

Being set back away from transom. you probably can raise the engine up about 1/12 - 2 inches higher than when on the transom

Thanx for that info,my local mariner/merc dealer tells me the powerhead was built by yamaha to meet mariner soecs and design.
I was under the assumption for every 1 ft back you can raise 1 in in elevation

 

[jimmbo]

I looked in the 1997 Mercury brochure and the specs showed the 4 cylinder 44(43.9) cu in configuration used for decades.

My 150 was raised 3 inches and its setback was about 13 inches. Just something for you experiment with.

 

[igotit]

But what was your wot speed.
Movement plays an important part on how high you can lift.
Im certin i can come up atleast 3/4 inch with no issues.

 

[jimmbo]

My top speed with that unit was 54 - 56 mph. At higher speeds the prop was partially out of the water, at lower speeds the water would rise up quick enough to keep it submerged. Up to 2 1/4 inches I was able to use the standard OMC Al prop, after that I had to use a highly raked and cupped prop(Raker) or it would blow out in turns while trimmed out

 

[b.gagnon]

That motor is going to get swamped every time he lets off the throttle too fast!

 

[igotit]

I just went for a test ride,everything worked out well.
She makes a little spray when i get off of plane.
Nowhere near as bad as i had expected.
I will add a plate on the bottom to solve that issue.
Ive also raised the motor 1 bolt hole higher and trimmed 2" off the bottom of the angle bracket.

 

[igotit]

Sorry so long since last update,blew the power pack on that last run.
Replaced today.

Im very pleased to report,today i trimmed another 1" off the bottom of the bracket,makes zero spray.
Didnt have to add a plate to the bottom.
Boat does a comfortable 32 mph,doesnt washout in turns and the cav plate is 3/8 th about bottom of the hull.
While riding the cav plate is about 1/2 below the waters surface.
Tomorrow ill to get a vid of the boat riding showing the motor during acceleration and fast decel.
Thanx fir viewing.

 

[jimmbo]

You should be able to raise it so the plate is just above the water

 

[JimS123]

That's a lot of cantilever to put on that transom. How old is the boat? I wouldn't be afraid to run the boat in the water, but I would be afraid of the dynamic stresses when the boat was being trailered down the highway.

Nice job with the fabrication. I'm looking at doing the same thing for a kicker on my new boat.

 

[igotit]

I was worried about the leverage effect on the transome aswell,the boat is about 2003,solid transom.but i also added plate to the inside aswell.
The owner is 280 lbs,he tested by standing on the cav plate and bouncing.
No transom movement.
I hit 3 ft swells today at 20 mph,she held up nicely.
She tops out at 34 mph with the 17 pitch prop @5100 rpm .
I suggested to the owner to drop down to a 14-15 pitch for better holeshot and load carring.

 

[jimmbo]

A 15 would put him at 5500 rpm, right at the top of the range. Numbers show 15% slip