Av plate questions

Pak713

Cadet
Joined
Apr 1, 2014
Messages
18
There are pictures of the motor an transom. Also to the other poster, I think my motor is in between a short and long shaft. I built a different motor mount that should fix this problem. I will post pictures of it when I get it finished.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Rig up something like a home made jack plate.
You can raise it an inch or so just by placing a 1" stick on the transom as you tighten the clamps,
The clamp does all the work, sitting right down on the transom doesn't really add much support.
Probably if you go on youtube search home made jack plate you'll get the idea.
No pressure treated in direct contact with the aluminum.
 

Pak713

Cadet
Joined
Apr 1, 2014
Messages
18
The new wooden engine mount I have made is made out of treated wood. The one that was one there before was treated also. I have a thin piece of rubber I could put in between the transom and the new engine mount. I heard treated wood will decay aluminum or something. But I figured since the one on there before was treated it would be alright. I planned on putting a water proof coating on the new engine mount as well. Would it be ok with the thin piece of rubber between the aluminum and wood? Thanks guys.
 

undone

Petty Officer 2nd Class
Joined
Jul 26, 2014
Messages
147
There is a different type of pressure treating used for contact with aluminum, it's not the normal stuff you get at the local big box store. Read the warning label on the normal stuff next time you get a chance.

Protecting the aluminum helps.
 

Pak713

Cadet
Joined
Apr 1, 2014
Messages
18
Alright can anyone tell me if painting, waterproofing or putting a polyurethane coating will keep the copper from really coming out of the treated wood. I'm also putting a thin rubber coating on the back of the mount where it comes in contact with the aluminum
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
If it was me I would try to isolate fasteners and material from the aluminum Some sort of neutral gooey compound.
The piece of rubber sounds good as well. Then keep an eye on things perhaps pull a fastener in a few months use to check it out.
I have a pt platform at our rear entrance I use salt sparingly in winter. The compatible deck screws are destroyed in about 18 months.
I now remove and replace the screws in the fall.
 

Pak713

Cadet
Joined
Apr 1, 2014
Messages
18
Ok everyone hopefully someone reads this and can help me out. So I never got to test my boat last year after making the jack plate. Recently tested it and around half throttle the water exhaust ports just below the av plate are above the water line and loose power. So I thinking the two inch raise was too much I guess. So should I lower the motor then?? Before I made the jack plate I never had this issue. The boat just wouldn't plane out. Just wanted to stand up. I was thinking that it was losing power because I wasn't getting enough water intake, but that can't be because the water intake is still under the water. Any help is appreciated. I tried to upload another picture but is says it was too big. So right now the av plate which is just above the water intake holes is level straight across with the bottom of the boat.
 

Fed

Commander
Joined
Apr 1, 2010
Messages
2,457
Recently tested it and around half throttle the water exhaust ports just below the av plate are above the water line and loose power.
I'd suggest you're losing grip due to the bubbles coming off the external keel rather than losing power.
Often external keels are tapered up towards the transom to help with this problem.
The AV plate is the one directly above the prop so those water ports are above the AV plate.
You need to find the happy zone for the height.
 

mlevee87

Cadet
Joined
Feb 11, 2015
Messages
18
YES those tachs work great for marine applications. Theyre supper easy to install as well. Just gotta mount it on the dash and wrap the end of the wire around the number one cylinder spark plug wire. I have one on my boat right now and my father has one on his. Paid $55 at tinytach.com. Theyre powered off of an internal lithium battery rated to last up to 7 years or something crazy like that. Worth every penny and accurate.
 

Pak713

Cadet
Joined
Apr 1, 2014
Messages
18
Yes you are right. The exhaust water parts are above the av plate. So even though they are exhaust water ports and not the water intake should they be below the water line? I'm thinking about dropping it an inch and then trying that. But I'm not sure I even need to go an inch.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
I know nothing about the 15 but I think those holes above the anti vent plate may be exhaust relief or perhaps water intake in reverse or at idle.
because in reverse exhaust may foul the regular water intake.
If you can lower the motor about 1/2 inch at a time. and play with the trim a ltitle.
In the old days ,wooden boats ,they suggested to taper about a foot of the rear of the keel for outboard operation.
I have an old Jophnson owners manual circa 1948 that refers to ventilation as cavitation.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Pak,

If you haven't tested your combo yet, that's a dry installation which says nothing. If you want to dial the sweet transom/engine height to get all the available ponies out of any portable engine you must.

-Have a healthy engine and prop
-Engine trimmed at 90?, perpendicular to water level, usually second, third trim hole out transom.
-Distribute weight evenly on deck, if riding solo move full gas tank up front.
-Go for a wot spin lightly loaded on flat calm no wind water cond.

That LU has a weird design, do you have a sharp one piece close edge between 3 and 2 no matter if rear of edge has those submarine type holes ?

Pak 713.JPG

If so, you need to raise or lower engine for water flow to skim right under 3 which is the upper small water deflector plate. That must be height dialed under trial and error, will need a aft spotter to check at which tail height is water flow passing at speed once on plane, provided that the 15 HP has enough punch to plane that 14 footer at good speed.

Once at the sweet height you can tach that engine with an induction tach to see if at least you're at middle to max wot rpm factory stated for that engine, can go from there maximizing prop if needed for best combo performance.


Happy Boating
 
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