Water over transom...

[jdunbar]

I have a 2012 tracker 1648 Grizzly with a 2011 15hp 4stroke Mercury. Just bought the boat last summer and have only had it out a few times, but at about 3/4 throttle water comes up between the clamp bracket and over the transom. Adjusting the motor trim does not seem to help. Any suggestions?

 

[Weldorthemagnificent]

Make some sort of deflector either out of aluminum sheet or a hard plastic that can be formed while warm. Clamp it between the motor and transom to hold it so you don't have to drill any holes.

Sent from my CLT-L04 using Tapatalk

 

[JL8Jeff]

Do you have any pictures showing the motor mounted on the boat? It might be mounted too high or too low causing water to spray off the cavitation plate.

 

[jtsull]

I agree with JL8Jeff. From my experience, height matters regarding splash back. I have a Grizzly 1448 with a 25 HP on a jack plate. I can run that motor's cavitation plate from 1" below the bottom of the boat to 4" above. Running at 3/4 throttle and adjusting the jack plate's height produces very different splash back actions.

 

[jdunbar]

The boat is currently on a lift at my cabin about 100 miles away, so I don't have quick access to take a better photo, but attached is one that I have. The motor is basically mounted with the clamps flush on top of the transom. I've adjusted the trim to different positions but not noticed much of a difference. I thought about getting a manual jack plate to dial in the best height to prevent this, but was just looking for other ideas before I do that. It does not seem like a jack plate should be needed to keep the motor from pushing water back over the transom on a small outboard like this.

 

[Shaugh]

You need to put a straight edge on the bottom of the boat and see where it is in relation to the cavitation plate. Likely the motor is too deep. If you imagine a boat at speed is like somebody under the boat with a fire hose aimed at the motor.... The plate and angled surfaces of the motor help keep that splash from going upward. The higher up you can see on the motor, the more surface area there is to splash against.

 

[ppine]

Engine depth is important, but you likely have a weight distribution problem.
Are the batteries, fuel tank and operator in the stern?

 

[LDUBS]

I kind of hesitate to post here because I can't offer anything productive (what else is new - Haha).

The idea that enough water is coming over the transom at 3/4 throttle to be a concern is kind of an eyebrow raiser for me. I assume we are talking about a heavy spray. The potential causes put forth so far seem logical.

I hope this thread stays alive and we get to learn the actual cause and solution.

 

[jdunbar]

Yes, fuel tank, one battery and the operator are in the back, but I also have a an extended deck in the front to balance out and only usually keep about 2 gallons in the 6 gallon tank.

 

[jtsull]

I assume the tracker 1648 has a 20" transom and the Merc motor is a long shaft (20")?
If the motor is anything like the 15-30 HP Suzuki, the long shaft motor is actually 21.5" so you may be below the bottom of the boat by a couple inches. If your motor is the short shaft (15") on a 20" transom, that could be the issue as well but I would think it would be sucking air if that high.

 

[whorrall]

I'd bet dollars to donuts that your motor is too low. Your cavitation plate should be even with the waterline when you're on plane. You can buy or make a riser block constructed from aluminum to allow your motor a little more height, or buy a jackplate. They make cheap manual jackplate with as little as 3" of setback. Vance makes a good and inexpensive one, and that's what I run.

 

[fyr4efect]

The boat is currently on a lift at my cabin about 100 miles away, so I don't have quick access to take a better photo, but attached is one that I have. The motor is basically mounted with the clamps flush on top of the transom. I've adjusted the trim to different positions but not noticed much of a difference. I thought about getting a manual jack plate to dial in the best height to prevent this, but was just looking for other ideas before I do that. It does not seem like a jack plate should be needed to keep the motor from pushing water back over the transom on a small outboard like this.

I have a grizzly 1448 with 20hp tohatsu tiller. My transom is 17.5 and the tohatsu short shaft is 16". Tohatsu manual says to mount the engine so the cav plate is 1/4' to 1" below the bottom of the transom.I was getting back spray over the transom at wot until I mounted a jackplate with 6" setback and lowered the engine. I believe the tohatsu 15/20 hp and merc 15/20 are the same engine [made by tohatsu] With a jackplate you can adjust your cav plate height. Good luck.

 

[lovedr79]

once i put a transom riser on my grizzly the spray was eliminated. my motor was about 1" above the bottom of the boat. my fuel tank was mounted under the console, trolling motor batter up front, anchor up front.I eliminated the starter battery in the back. ran 3ga wire to the trolling motor battery for the starter. i also learned not to chop the throttle from WO to idle. the water would get close to the top of the transom if i did.

 

[whorrall]

The boat is currently on a lift at my cabin about 100 miles away, so I don't have quick access to take a better photo, but attached is one that I have. The motor is basically mounted with the clamps flush on top of the transom. I've adjusted the trim to different positions but not noticed much of a difference. I thought about getting a manual jack plate to dial in the best height to prevent this, but was just looking for other ideas before I do that. It does not seem like a jack plate should be needed to keep the motor from pushing water back over the transom on a small outboard like this.

I have a grizzly 1448 with 20hp tohatsu tiller. My transom is 17.5 and the tohatsu short shaft is 16". Tohatsu manual says to mount the engine so the cav plate is 1/4' to 1" below the bottom of the transom.I was getting back spray over the transom at wot until I mounted a jackplate with 6" setback and lowered the engine. I believe the tohatsu 15/20 hp and merc 15/20 are the same engine [made by tohatsu] With a jackplate you can adjust your cav plate height. Good luck.

In my opinion when companies say where to mount your cavitation plate in relation to the keel line, it is a shortcut for doing what you really should be doing, which is running your boat and seeing where the cavitation plate is in relation to the WATER level at plane (which as you know is different than the keel line). As you know the water on plane line level differs based on your setback and boat's loading/draft. I tweak all my setups with a jackplate like you do for best performance. Boat and motor manufactures tend to mount motors too low to avoid any liability for someone who raises their motor as high as it will go and then takes a sharp turn at WOT. 99% of people are happy with 90% of their performance and fuel economy.

 

[fyr4efect]

The boat is currently on a lift at my cabin about 100 miles away, so I don't have quick access to take a better photo, but attached is one that I have. The motor is basically mounted with the clamps flush on top of the transom. I've adjusted the trim to different positions but not noticed much of a difference. I thought about getting a manual jack plate to dial in the best height to prevent this, but was just looking for other ideas before I do that. It does not seem like a jack plate should be needed to keep the motor from pushing water back over the transom on a small outboard like this.

I have a grizzly 1448 with 20hp tohatsu tiller. My transom is 17.5 and the tohatsu short shaft is 16". Tohatsu manual says to mount the engine so the cav plate is 1/4' to 1" below the bottom of the transom.I was getting back spray over the transom at wot until I mounted a jackplate with 6" setback and lowered the engine. I believe the tohatsu 15/20 hp and merc 15/20 are the same engine [made by tohatsu] With a jackplate you can adjust your cav plate height. Good luck.

In my opinion when companies say where to mount your cavitation plate in relation to the keel line, it is a shortcut for doing what you really should be doing, which is running your boat and seeing where the cavitation plate is in relation to the WATER level at plane (which as you know is different than the keel line). As you know the water on plane line level differs based on your setback and boat's loading/draft. I tweak all my setups with a jackplate like you do for best performance. Boat and motor manufactures tend to mount motors too low to avoid any liability for someone who raises their motor as high as it will go and then takes a sharp turn at WOT. 99% of people are happy with 90% of their performance and fuel economy.

You'd figure since tracker just uses Merc why design a transom that's too short for a long shaft and too long for a short shaft? They wanted to give me something to do maybe.

 

[whorrall]

You'd figure since tracker just uses Merc why design a transom that's too short for a long shaft and too long for a short shaft? They wanted to give me something to do maybe.

You sure would, wouldn't you? But it has been my experience that boat manufacturers and even shops that install motors do not care about making your setup the best it can be. They care about getting the job "done", moving onto the next boat, limiting their liability, and getting paid. I've owned 6 tin boats over the years (1440, 1752, 1648, another 1648, 2060, 1872) all of them except for one were dialed in wrong. The one that was setup right in regard to motor height and prop I bought from a guy who understood boats and set it up correctly. Those people who actually take the time to learn, listen, and take action to make something work better are unfortunately in the minority.

 

[CedarRiverScooter]

Maybe a waterproof camera could be positioned so that you can see how the water is flowing past the transom at speed. Then you wouldn't have to guess what the problem is.

 

[fyr4efect]

You'd figure since tracker just uses Merc why design a transom that's too short for a long shaft and too long for a short shaft? They wanted to give me something to do maybe.

You sure would, wouldn't you? But it has been my experience that boat manufacturers and even shops that install motors do not care about making your setup the best it can be. They care about getting the job "done", moving onto the next boat, limiting their liability, and getting paid. I've owned 6 tin boats over the years (1440, 1752, 1648, another 1648, 2060, 1872) all of them except for one were dialed in wrong. The one that was setup right in regard to motor height and prop I bought from a guy who understood boats and set it up correctly. Those people who actually take the time to learn, listen, and take action to make something work better are unfortunately in the minority.

[/quote][/quote]

I think most boat owners are hesitant make holes in their transom [rightly so]and aren't use to wrenching/fabricating. I had fun with the process of dialing mine in, especially when it worked. Lots of good/helpful info on this site. Dealers not so much.

 

[jtsull]

You'd figure since tracker just uses Merc why design a transom that's too short for a long shaft and too long for a short shaft? They wanted to give me something to do maybe.

Spot on. I thought I was the only one that just didn't get why Tracker would do that. Build a jon boat with a 17 1/2" transom.

 

[jcunard]

I had the same issue as the original poster but with a 2013 15HP long-shaft Mercury on a 14 foot Lund with a 20 inch transom. The motor was originally installed with the transom bracket flat against the top surface of the transom. This put the cavitation plate about 2 inches below the bottom of the boat. The dealer reinstalled the motor with a 3/4 or 1 inch piece of starboard between the top of the transom and the clamps. This was as high as he could go and still allow the clamps full contact with the transom. This increase in height was enough to eliminate the spray over the transom.

No guarantees but the original issue sounds alot like mine.