Is the motor low enough in the water????

[inshore-gasm]

I have a 21 1/2 transom on my smoker craft 16 footer v hull. From my measurements the waterline (at full plane) would be right above the water pump screens,those plastic pieces on the sides that you hook the ears up to flush the motor. in other words,the bottom of the boat is even with the top of the water pump screen. Were should the bottom of the boat line up with the motor for the best results. I have a jack plate but I don't want to use it because the motor wont trim all the way up with it on because the motor hits the transom. Am I going to need to cut the transom down? Or just use the jack plate anyway? I am replacing the 25hp that was on the boat with a 60 hp Mercury 2 stoke. I am thinking this is why the little 25 was on a jack plate.

 

[inshore-gasm]

Re: Is the motor low enough in the water????

Im just wondering why no one replies to my posts? Am I doing something wrong?

 

[ondarvr]

Re: Is the motor low enough in the water????

Im just wondering why no one replies to my posts? Am I doing something wrong?

Well, its fairly early in the morning in some parts of the country and its only been half an hour. The other part may be that this might not be the correct section (Boat Restoration, Building, and Hull Repair) for this question.

I think you may need to supply more info and possibly a pic. What is the shaft length of the 25 and the 60?

 

[BaileysBoat]

Re: Is the motor low enough in the water????

Setting the top of the AV plate even with the bottom of the boat is a reference point for installation, the final engine height to be determined by testing. The measurement you give sounds high for everyday use.

Agree a pic would be good.

 

[NSBCraig]

Re: Is the motor low enough in the water????

Yeah that's probably why the jack plate was there.

Start with your av plate even with bottom of hull.

 

[inshore-gasm]

Re: Is the motor low enough in the water????

Here i am showing how I am taking the measurements

 

[inshore-gasm]

Re: Is the motor low enough in the water????

Im thinking the AV plate is at the 18 1/2 point on the tape?

 

[inshore-gasm]

Re: Is the motor low enough in the water????

[/IMG]
The measurement of the transom is about 20 3/4

 

[inshore-gasm]

Re: Is the motor low enough in the water????

 

[inshore-gasm]

Re: Is the motor low enough in the water????

I dont know what the AV plate is. Im thinking it is the first flat plate above the prop?

 

[inshore-gasm]

Re: Is the motor low enough in the water????

You can see were the 20 3/4 point is. So that would be the bottom of the transom right? And im thinking that is not enough motor in the water?

 

[ondarvr]

Re: Is the motor low enough in the water????

If the water intake is below the waterline when on plane, then cooling won't be an issue, but that doesn't mean the motor is mounted in the best location.

Back up and show a pic of the motor and transom together (motor mounted on transom), like the others said, the AV plate should be even with the bottom of the transom, or slightly higher. This is just a starting point, for best performance you need to move it up and down to find the best location for how you plan to use the boat.

 

[inshore-gasm]

Re: Is the motor low enough in the water????

I haven't mounted the motor on the boat yet because I am making a brace for the transom,just to add strength. I dont know what the AV plate is. I want the boat to sorta lift out of the water when I have the peddle to the meddle. I think for that to happen, I would need to put stabilizers on the plate above the prop and have the stabilizers about 1'' under the boat????. That is just what my mind tells me to do but I am not in denial...I am far from a professional! This boat will be carrying dive tanks and possibly a few people and that is why the 25 hp was not enough. The boat is rated for a 60hp but that was back in 1980. Please let me know if you foresee any issues with what I am thinking. Thank you all for helping me with this you have no idea how much I love this site!!! :redface:

 

[westexasrepublic]

Re: Is the motor low enough in the water????

http://www.marinepartsman.com/installing-an-outboard-on-your-boat.html

 

[ondarvr]

Re: Is the motor low enough in the water????

The AV plate is the flate plate you asked about mounting the "stabilizers" on.

You don't want to mount anything on that plate at this point, and it will be out of the water when adjusted correctly.

 

[ufm82]

Re: Is the motor low enough in the water????

The "AV' plate, or anti-ventilation plate is the large horizontal plate directly above the prop. It is there to force water down on the prop when taking off, preventing "ventilation" or the sucking of air from above the prop into the water. That prevents the prop from losing its bite and that gives you the holeshot or take-off from a standstill or slow start.

The plate should be 1"-11/2" ABOVE the lowest part of the keel on the boat. That prevents it from dragging in the water when the boat is on plane. Having it even with the bottom will result in excessive drag and handling issues like porpoising.

Remember that even though the water intakes may "look" to be high, the boat will sit "down" in the water. As you move forward, the water will move up from under the boat and cover the intakes. If the engine is set-up correctly you won't get cooling issues.

Mount the engine so that you have room to adjust height and then go from there. Start where I said to and go up as needed. You don't want to go below the 1" mark.

UFM82

 

[inshore-gasm]

Re: Is the motor low enough in the water????

@ufm82- Thank you very much! from my calculations it would be exactly 1 1/2" above the base of the transom! That makes me happy! BTW what is porpoising? My old 15' bass boat had a 120 evinrude on it and it would completely lift out of the water when I started trimming the motor up. It would go from 58mph up 67mph But it felt like it was unstable from side to side. That boat almost killed me because my brass balls got in the way,not to mention the testosterone and gasoline mix!!! ..