This is what I do know,I can put a 3/4-1 inch shim under my motor now to get the av plate almost close to level with the keel,I think I would be comfortable there. I won't go any higher because I don't want to chance the motor over heating even it may never over heat with it higher. I can't see how this motor wouldn't perform well if the av plate was really close to dead even of the keel give or take a cm. I know my manual says do not go any higher then level with the keel. It says anything from level to one inch down is were it needs to be to perform at it's best,that is in my manual. Maybe I will just deal with the motor the way it is and put just a shim under it. I figured a small wood shim would do it,then I will clamp it down hard and go test it out,if it works well I will just bolt it down. One more thing,when I opened the box there was only two bolts for mounting the motor,is there any advantage to using the top or bottom holes? I guess two is enough because they supplied the hardware.
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Anti ventilation plate height
- Thread starter scoobeb
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Skiffing
Well-known member
scoobeb said:
It may not be worth it for you to do anything!
Speed performance gains on boats like ours will be minimal. Fuel efficiency will be increased though. I doubt most guys in small boats meter their fuel use or know what the GPH consumption is at any RPM. It's not like you've got twin 454's that gulp 35 gallons per hour [EACH]
In my case - I tweaked the engine height a few times and can now cruise at 24mph @ 4700 RPM. WOT is 29mph @ 5600 RPM. Fully loaded boat is 1360 lbs. Fuel burn is 7.5 miles per gallon. Merc publishes 4.8 gallons / hour @ 6000 RPM for my engine. This tells me I'm getting good efficiency.
Lots of guys could care less about this - they want to fish and enjoy. For some of us, though, this is part of the fun.
I will make 1/2. 3/4 1. Inch shims to see what works for the best height without going higher then the keel,I just hope I have enough transom left to clamp . I found quite a few forums I just read were guys just lifted their motor with wood shims like I want to and just used the clamps and never bolted it down and they never had any issues. Now of course if I do this I will still have that cable lock to make sure if it ever popped up it would get caught by the cable. When I clamp it down,I clamp it down,it would take some extremely serious force to pop the motor off the transom.the good part is if I move the motor up the clamps will be actually be sitting under the lip of the top of the transom for extra security. So all in all I believe I will try that first,shims.
I'm one of those people who loves watching the boat videos on YouTube,I love watching them. Almost all the small jon boats like ours run with the av plate under the water and they still run fast. I never said that was right but most If nit all those people are not educated like myself being uneducated on how to perfectly tune an outboard. I see your point though,I'm only going to get so much speed and performance out of a jon boat. I'm not to overly concerned about losing a mph like I said but it would be nice to have electric start and power trim and tilt for only few hundred more. I should just say screw it,mount the sucker on and go fishing,but this is in my head now and my ocd is kicking in,lol.
Bowhunter1661
Well-known member
I am just one of those crazy fellows that loves to tinker with my boat. If there is even one thing I can POSSIBLY make better, I m doing it! To each his own, this is just my .02 cents. My boat performed well when I had zero adjustments made to it, now it performs great. I get a lot of enjoyment and satisfaction out of perfecting my setup.
Skiffing
Well-known member
^^^
If you're not anal you're not a good hunter
If you're not anal you're not a good hunter
Well here is my plan,buy 1/2-3/4-1 inch shims,use the one that gets me dead even with the keel of the boat which should give me the best performance,clamp on the engine as much as I can,stop thinking about this anymore,enjoy my boat and go fishing. :mrgreen:
Bowhunter1661
Well-known member
If this helps at all, here is where my motor is at with the jack plate. However I did raise it another 3/4" from this point to get it right on.
Like I said I will lift mine as high as the transom will let me with having enough bite for the clamps to lock down on. Then I will just use it and be happy. Unless it just performs horribly I will leave it as be. As long as my wot with one or two people is near 30+mph I will be ecstatic and satisfied.
Bowhunter1661
Well-known member
Wonderful! Enjoy!
I saw your video on YouTube,pretty cool. So what kind of wot are you getting to see if I'm in the same ball park. My boat should scream with this new 25hp. I'm hoping 30-33mph with one person and at least 28-30mph with two people.
Bowhunter1661
Well-known member
Yeah that video was horrible, you kind of have to lay your phone flat and turn it to view correctly. Still trying to get use to this new phone. If you don't have casting decks or all the bells and whistles I have that sounds like a realistic speed. After all, my Boat is loaded to the gills and I saw 32 mph show up on my GPS but I could cruise all day at 31.
Bowhunter1661
Well-known member
But I should also add that I am running a 15 pitch prop and turning 5400 RPM at WOT.
Charger25
Well-known member
10 X 15 ? you guys are make me buy a new prop and buy/ build a jack plate before it over :LOL2:
Bowhunter1661
Well-known member
Charger25 said:
Lol, I was shocked when I bought this motor to see a 15" prop on it! But it turns it great! The added height certainly helps with getting the RPMs up
Bowhunter1661
Well-known member
Also, I may or may not be ordering a 35 carb and intake for my motor. 8)
I have watched so many videos my head is spinning,lol. Over 95% of the people that own jon boats run with the anti ventilation plate under water and almost all the rigs fly except for the ones that are way underpowered. Most of the guys trying to get their height right were large boat owners. Like I said though most of the videos had the plate buried but still flying on the water. Yours was about the only fine tuned outboard out there. So now if say I move my engine up to even with the keel by putting a shim under the engine and run over 30mph wouldn't that be great considering your rig is as fine tuned as you can get and your prop is a 15 pitch so it's 3 pitches bigger then mine. I would be good then,right?
There is a website called media channeslblade.com that explains about engine height. It states that standard height is 1-2 inches below the keel for slow speed as I would guess our boats,under 40mph. Then it has even with the keel for average speed,also our boats I would guess again under 40mph,then you have 2-4 inches above that states high performance speed boats. So all in all 1-2 inches below the keel to even with the keel seems to be were most people end up setting their rig up.
Bowhunter1661
Well-known member
At that point, yes, I would call it good. The reason I can raise mine so high is due to the setback the jackplate gives me. When the water passes under the boat and exits behind it immediately starts to rise, due to the fact your hull displaced it. Yours being mounted directly to the transom with no setback should be just fine at even with the transom. Possibly a little digging in, but not a lot.
My boat is heavier due to all of the accessories I have, including decks, trolling motor, battery ESC... Therefore when planing it does sit slightly deeper than an empty boat. That's why I need my motor to be higher, because my boat drafts deeper, as well as mentioned before. The water rises up to a higher level where my motor is setback to.
Imagine this in your head. Your flying at 30 mph, boat is sitting level ON TOP of the water. Maybe drafting 1" when on plane. If the AV plate is level with the keel, the water is flowing Beneath the boat and slightly raising as it exits under your keel. You should be right on, or darn close with the AV plate adjusted level with the keel.
My boat is heavier due to all of the accessories I have, including decks, trolling motor, battery ESC... Therefore when planing it does sit slightly deeper than an empty boat. That's why I need my motor to be higher, because my boat drafts deeper, as well as mentioned before. The water rises up to a higher level where my motor is setback to.
Imagine this in your head. Your flying at 30 mph, boat is sitting level ON TOP of the water. Maybe drafting 1" when on plane. If the AV plate is level with the keel, the water is flowing Beneath the boat and slightly raising as it exits under your keel. You should be right on, or darn close with the AV plate adjusted level with the keel.
So I'm going to use a wood shim,anything I should treat it with to last me a long time? Also I don't know if I have enough bite on the transom to go perfectly level with the keel but I'm going to get as close as possible. I may be a 1/4 inch off but that's better than were I am now.
