Installed motor height.

dstockwell · Post by **dstockwell** » November 29th, 2004, 1:40 pm

The most I get is still 37MPH @ 5 K, can not get over 5k and Merc says 5250 - 5750. Cav plate is even with bottom, some say mount motor so it is an inch below cav plate. What will this do, when it allows me to trim. Currently if I try to trim very much boat will porpoise and speed falls off. Another prop is not an option unless the dealer has one I can swap out with.

Post by **wevans** » November 29th, 2004, 1:53 pm

If it is supposed to be running 5250 - 5750 WOT, you will need to drop your prop pitch by 2 or 3 inches "but expect your speed to either decrease or stay about the same"

dstockwell · Post by **dstockwell** » November 29th, 2004, 2:07 pm

That makes no sense, well it does, but a 200 Merc and 3000 lbs fairly loaded boat should swing that 14 1/2 X 17 to Max RPM..

Post by **wevans** » November 29th, 2004, 2:17 pm

I can't imagine a 200 needing to go below a 17 pitch, but it can happen

I would either take the boat in to the dealer or at least give them a call and discuss it with them

Post by **Tom Keels** » November 29th, 2004, 2:29 pm

Motor is mounted too low. Raise it a hole and try it.

Post by **Chalk** » November 29th, 2004, 2:50 pm

Raising it a hole is the cheapest thing you can try......Or...lookup a local prop shop(not a boat shop)...I know there's one in Pensacola...Changing props around will be the easiest....Get your prop number and size and call Key largo and Mercury and see what they say...That will be free...Call the company direct......

Post by **wevans** » November 29th, 2004, 2:59 pm

It's hard to tell for sure, but the motor looks about right

dstockwell · Post by **dstockwell** » November 29th, 2004, 3:21 pm

Look like it yes. I called another Largo dealer and they said install Bobs Machine shop

to change the angle..

Post by **Chalk** » November 29th, 2004, 3:48 pm

Your in the top hole you have two to try.....

Post by **tin can** » November 29th, 2004, 3:51 pm

MOTOR HEIGHT

From looking at the picture above, the motor is too low.

1. Using a builder's level, and the tongue jack on the trailer, level the keel of the boat.

2. After the boat keel is level, use the trim on the motor, and the level, to level the cavitation plate on the motor.

The boat keel and cavitation plate are now parallel.

3. Place the level on the keel and extend it out the back of the boat until it touches the leading edge of the lower unit. Mark the spot on the lower unit where the top of the level touches.

Where is this mark in relation to the cavitation plate. If it's more than 1/2" below the cavitation plate, raise the motor. The holes in the motor mount bracket are spaces 1" apart. Raise the motor until the cavitation plate is even with, or just above the bottom of the boat.

WEDGES

The wedges you have pictured are not necessary if you are not having a hole shot problem. If the boat gets up good, don't install the wedges.

PROP

NO TWO PROPS ARE THE SAME! You can run two props, of the same make, with the same pitch and diameter, with the same part number, and they will run diferently. If raising the motor does not achieve the desired RPM, the least expensive way to remedy your problem is to have your prop customized. What brand prop are you running? If memory serves me, when you went through this the first time you ran the boat, its a Michigan Wheel prop. If that's the case, You probably need to have the leading edges thinned, have the diameter reduced by 1/8", and have the tips cupped. If you're interested, all this costs about $160.00.

Ask me how I know all of this.

Post by **tin can** » November 29th, 2004, 3:55 pm

OH, I forgot TRIM.

More than likely, you'll never be able to trim your motor to the max without the boat bouncing. On that type of hull, you don't need to. Most of the offshore boats run well at about half trim.

dstockwell · Post by **dstockwell** » November 29th, 2004, 10:30 pm

John,

I leveled the keel at the rear was not sure if that was correct, and in order to level the cav plate I was 1/4 into the trim, after both of these the cav plate was level with the keel, right on the money. However a design problem may be why the other Largo dealer told me to use the transom wedges and lower the motor to the first hole, its currently in the second.. Basically the 206 is a short 236, however they took three feet off the end instead out of the middle.

Looking at the transom angle in relation to the motor its about 5 1/2" from transom angle / to | which is my level or
.. / |
../ .|
./ ..| the gap is about 5 1/2, so in order for the cav plate to be level to the keel it must be trimmed about 1/4 into the trim.

The (1 inch) 5 degree cast aluminum wedges are used as an aid for boats with an insufficient transom angle. Since its really not feasible to trim up, and the boat runs best with the motor tucked under, would lowering it 1" below the keel and adding the wedes enable to trim up enough to gain the RPM.

Post by **tin can** » November 29th, 2004, 10:47 pm

You should be about 1/4 trimmed to get the cavitation plate parallel to the keel. If the keel is even with the bottom of the boat, you should be alright.

I put wedges on the TCII because the transom was almost perpendicular to the bottom. The boat would bounce with the motor trimmed all the way under. Your transom angle should ge around 16 degrees from perpendicular to the bottom. If it's less than 15 degrees, and you're having trouble getting the boat on plane, you might want to try the wedges. If the boat comes up good, I wouldn't put them on. All the wedges do is ad 5 degrees of transom angle. They will tuck the motor further down on takeoff, and allow you to trim further, because you've increased the transom angle. They won't affect your RPM.

I would try raising the motor another hole. That will put the cavitation plate 1" above the bottom. If it doesn't blow out on takeoff, I'd run it high.

Next time you run the boat, have someone else hold the wheel for you at WOT. Look out the back of the boat and check if water is going over the cavitation plate, or the plate is skimming the surface. If water is going over the top of the cavitation plate, raise the motor. You still have 2 adjustment holes. The higher you have the motor, the less drag. If you lower the motor, it will create more drag. I have never seen an instance where lowering the motor increased RPM.

If this doesn't solve the problem, have your prop fixed. I'll get you a number to a gentleman that knows how to make a prop preform.

dstockwell · Post by **dstockwell** » November 30th, 2004, 7:55 am

Thanks.. I have on hole up, and three down, so will see the next time.

Post by **wevans** » November 30th, 2004, 8:40 am

I'll get you a number to a gentleman that knows how to make a prop preform.

Me to TC

I need ta lower my RPM's with this new hull