Outboard spraying water into boat

[wineyarders]

Hi,

I've been lurking here for a while and figured I'd post up a couple issues I'm dealing with on my small 12' skiff. Hopefully someone has the solution I'm looking for. As I understand it, the plate at the base of the midsection should be even with the bottom of the stern. If t is lower it will cause spray. My question is, how do raise the engine up? I could bolt a piece f wood into the hanging bracket or something, but that seems a bit strange. Any ideas? Thanks,

Ryan

 

[Scott Danforth]

Re: Outboard spraying water into boat

do you have a long shaft motor on a short shaft transom? or do you really have a short transom?

 

[southkogs]

Re: Outboard spraying water into boat

Welcome aboard Ryan:

What size HP are we talking about here? I've had spray pop up about 10" off the back of the boat when we had her loaded weird and it didn't trim out right. In a 12' skiff are you running more than 15HP, and what's the max the boat is rate for?

 

[wineyarders]

Re: Outboard spraying water into boat

Thanks for the welcome. The boat is a stock 12' aluminum skiff, I think an older model lowes that is rated up to 9.9 hp, but I think the Johnson 9.9 and 15 are the same size. The engine was converted to short shaft. The spray will shoot up 2-4' with most staying out of the boat. Not a huge deal, but not great when I'm trying to stay as dry as possible. My biggest concern with raising the engine an inch or 2 is what affect it would have on stability. This thing in the ocean can feel pretty small.

 

[southkogs]

Re: Outboard spraying water into boat

9.9 and 15 are roughly the same size, but on a 12 footer make a huge difference. We have a 14' that's rated for 10 or so ... we plopped the 15 on the back of it once just for fun: turned out more scary than fun on that boat.

12' aluminum - 3 benches - oarlocks if you wanna' row it - that's what you have correct? And you have a 9.9 short-shaft on the back, getting 2 - 4' of spray off the sides of the outboard? Have you trimmed it all the way in to the boat?

 

[nwcove]

Re: Outboard spraying water into boat

sounds like you need to make some adjustments, as mentioned, that much spray is to much. try tilting your motor in/out a bit, or its way to low in the water.

 

[wineyarders]

Re: Outboard spraying water into boat

Thanks for the replies and advice. I've never played with the tilt since the pin is totally seized/rusted out. Guess I may need to drill this out and replace. One question, I'm having a hard time finding how to adjust this pin (i.e., how to use it), including looking at sschapetra and the manual. Anyone have any advice on how this adjustment works? Thaks again,

Ryan

 

[Outsider]

Re: Outboard spraying water into boat

This thing in the ocean can feel pretty small.

That's probably because it IS small, particularly in the ocean. When the tilt pin is close to the transom, thrust will tend to raise the transom and lower the nose; use when stern loaded. When the pin is moved away from the transom, the tendency will be for the bow to rise; use when bow loaded. The happy medium is the position which gives the best ride for the load at that time.

Positioning the plate even with the bottom is a starting point to fine tune best position. Get the tilt correct, then see what it does. Any spray should fan out pretty much parallel to the water surface ...

 

[wineyarders]

Re: Outboard spraying water into boat

Since the engine is already big for the boat I need to keep the pin close to the transom (currently could only move it up 1 slot), which brings me back to square one. Anybody have thoughts on how to bring the plate in line with the bottom of the transom? Any chance this could be the result of a converted longshaft?

 

[Mi duckdown]

Re: Outboard spraying water into boat

Pics would help.

 

[Sea Rider]

Re: Outboard spraying water into boat

Spry entering into boat at leg area is mostly due to water flow hitting non triangular exhaust portion at rear tail instead of passing through the triangular tail portion that cuts well water flow, will need to rise the engine up a bit untill water flow passes neatly cut. Distribute passengers well and trim properly your engine to have a paralell cav plate to water surface when on plane. Which brand and HP is that engine of yours ?

Happy Boating

 

[sublauxation]

Re: Outboard spraying water into boat

You sure the water is coming off the motor? In case you haven't already addressed this, my speedo pitot can throw a lot of water when weighted wrong and before I adjusted my depth finder transducer it through up a wall of water as well.

 

[Outsider]

Re: Outboard spraying water into boat

Uhhh, Sea Rider, I believe the ideal flow is just under the cavitation (anti-ventilation) plate. What you have depicted would create excessive drag, splash, and kill any performance ... :facepalm:

 

[Sea Rider]

Re: Outboard spraying water into boat

Uhhh, Sea Rider, I believe the ideal flow is just under the cavitation (anti-ventilation) plate. What you have depicted would create excessive drag, splash, and kill any performance ... :facepalm:

It's not a issue about beliving, you must be sure where water flow is passing to start correction from there, all brands tails are not same, as long water flow passes through the triangle area no splash problem, if at tight turns you experiment airation/cavitation issues your engine is too high on transom.

Happy Boating

 

[wineyarders]

Re: Outboard spraying water into boat

After a little thought I think the anode on the port cavitation plate is kicking the water up. Anybody have thoughts on this? Can the anode be moved?

 

[Frank Acampora]

Re: Outboard spraying water into boat

Sea Rider: I agree with outsider.

First, the cavitation plate is not a cavitation plate but an ANTI-VENTILATION plate. Its purpose is to keep the low pressure developed on the front of the prop blades from sucking in surface air and ventilating the prop. This ventilation can lead to cavitation, thus the misnomer: cavitation plate. The correct position of the anti-ventilation plate is either just at the water surface or very slightly below it.

Second: any time water passes an object, whether streamlined or not, some will tend to ride up that object. (Look at the bow of a moving supertanker) This is prevalent on outboards. The purpose of the top plate you have shown in the photo is to deflect this water out and downward. Without this deflection plate, at high speeds, water will climb the leg and enter the splashwell. When the engine is set too deeply in the passing water flow, even with the deflection plate, water will splash into the boat. Additionally with the engine set too low on the transom, more drag will be devloped with a loss of some top speed.

And I do not believe that, I know it.