Is my engine mounted low enough?

[Sailor96]

Hi everyone,

Recently I installed an old mercury 25hp on my sailboat.
The anti ventilation plate is about 1 centimeter under water.

I am worried tho, that my engine is mounted to high.
Does it have to be lower than this or is this fine?

It's a heavy boat (4000kg approx)
The engine also is getting cooled and runs fine.

 

[racerone]

Engine needs to be lowered about 10" for proper propulsion on a sailboat.

 

[Sailor96]

10 inch? Then the bracket would be underwater too, I don't think that's right.

Top of wooden plate where the engine rests on towards the waterline is about 40 cm I think. Lowering it another 10 inch would mean it's almost completely underwater.

Also I must point out that I do not need the engine to perform in the best possible way. If I can get away with a little less I'm fine as it's 25 hp and I only need it to get in and out of the marina.

 

[airshot]

Not sure about 10 inches but from that pic, another 5-6" deeper would be better. Right now the cooling intake is just barely deep enough, better to be a little deeper !!

 

[racerone]

I have been around sailboats since 1980.----I would not leave the marina with a motor mounted like that.----Hopefully you installed a new impeller in the 1984 / 85 motor every 5 years.

 

[garbageguy]

Not sure about 10 inches but from that pic, another 5-6" deeper would be better. Right now the cooling intake is just barely deep enough, better to be a little deeper !!

agree
To the OP - also think of where the bottom of hull is, in relation to the lower unit

 

[Sailor96]

The biggest issue is that I have a transom that does not touch the waterline. I was afraid it would be a little bit too high, especially when it gets wavy.
However, it's gonna be difficult to lower the bracket. It can maybe be lowered about 1 inch but that's it. Any other ideas on reducing the height? What about altering the wooden plank? There is space for that but wont that comprimise the strength/security of the bracket?

Picture below is taken when bracket was folded up. In that position the lowest part of the engine barely touches the waterline. First picture in post #1 is in the folded down position.

I added a drawn picture of the same boat as mine, I don't think the inboard prop is that far under the waterline. I have a keel boat that sticks like 1,40 meters deep.

 

[racerone]

Missed the part about the bracket being in the UP POSITION in post #1 !!----So what is the concern here ???

 

[Sailor96]

Missed the part about the bracket being in the UP POSITION in post #1 !!----So what is the concern here ???

No the first picture is in the down position. My bad.
My transom is angled, so I'm guessing that's why there's no much difference between lowered and not lowered, it doesn't lower that much.

 

[flashback]

A little chop and that prop will be sucking more air than water.. you really need to get it down..

 

[flashback]

Looks like you could lower the mounting board on the bracket and get 3 or 4 inches..

 

[Sailor96]

Looks like you could lower the mounting board on the bracket and get 3 or 4 inches..

Do you mean the wooden plate where engine goes on? The plate that is mounted to the bracket? I can probably cut off a good amount of it. Will it not compromise the strength?

 

[racerone]

Get an extension kit.---Add 5" to the length of the motor

 

[flashback]

Do you mean the wooden plate where engine goes on? The plate that is mounted to the bracket? I can probably cut off a good amount of it. Will it not compromise the strength?

Yes but I think I would just re-drill the mounting holes so you can move it back up if needed.. don't cut it.

 

[Sailor96]

Get an extension kit.---Add 5" to the length of the motor

Can that be done on an outboard thats already a long shaft like mine? Seems a bit expensive too. Would probably cost more than the engine did haha

 

[racerone]

Have you established a price for a kit ??----Why do think this suggestion is funny ??

 

[Sailor96]

Have you established a price for a kit ??----Why do think this suggestion is funny ??

I don't know? Are you trying to be funny?

Sorry but if you are suggesting a 1000 euro kit for an outboard thats barely worth half of that, yeah I find that funny...

 

[KJM]

Some people make a wedge that goes between the sloped transom and the motor bracket so that the bracket is mounted in a more vertical position. This might help some. Also some brackets have more vertical travel then others, you could look at that as well. That motor really should be a little deeper.

 

[racerone]

I think you need a bigger boat.

 

[Sailor96]

I think you need a bigger boat.

You must be fun at parties.

Some people make a wedge that goes between the sloped transom and the motor bracket so that the bracket is mounted in a more vertical position. This might help some. Also some brackets have more vertical travel then others, you could look at that as well. That motor really should be a little deeper.

I ordered this bracket becuase it allowed to be mounted on an angled transom ( negative or positive up to 35 degrees to avoid having a slope under the bracket). Becuase of this, I think it trades in alot of the lowering it would do if the transom was not angled. It wasn't a cheap bracket so I don't want to get a cheaper bracket and build a slope for it while I already have this. I think its better to try and lower it. I'm going to try flashback's suggestion and redrilling the holes in the wooden board to lower the engine a few cms. It should do the trick. Will update here later if it did or not.