Question about Propeller Clearance

[NJ Gonzo]

The lake we boat on is getting low due to drought conditions.

I have never seen the underside of my boat (we keep it at a marina and they store it over the winter.)

The depth gauge on the dash reads 2.5 feet when docked in my slip. I assume that this measurement is taken from the bottom of the hull. So my question is.... Does anyone know how far below the hull the prop hangs. Or more specifically, at what depth should I be concerned running it with 0 trim?

I have a Sea Ray Sundeck 220 with a Mercruiser 5.0L MPI 260HP Engine.

Thanks in advance for any advice.

 

[hottoddie]

The question should be what does your boat "draft". An IO boat like yours would be between 2 1/2 and 3ft of draft. How deep is the water? Use a boat pole or a 2X4 and lower it over the side of the boat in a few spots. If your depth gauge is reading 2.5ft I would guess the transducer is about 1.5ft below the water line of the boat giving you about 4ft of water depth. That's cutting it close. You don't want to run in water that shallow and stir up mud the can damage the water pump and clog up the cooling system.

 

[Espos4]

The lake we boat on is getting low due to drought conditions.

I have never seen the underside of my boat (we keep it at a marina and they store it over the winter.)

The depth gauge on the dash reads 2.5 feet when docked in my slip. I assume that this measurement is taken from the bottom of the hull. So my question is.... Does anyone know how far below the hull the prop hangs. Or more specifically, at what depth should I be concerned running it with 0 trim?

I have a Sea Ray Sundeck 220 with a Mercruiser 5.0L MPI 260HP Engine.

Thanks in advance for any advice.

I’m similar but slightly bigger (2007 240 SD) My depth is set so it reads “water depth below the hull” you’ll need to go through you transducer settings to see if any offset has been programmed in.
For reference, With 2.1 feet on my depth reading, I can accelerate and get up on plane. We’ve got sand and soft mud all around us, no rocks.

 

[NJ Gonzo]

The question should be what does your boat "draft". An IO boat like yours would be between 2 1/2 and 3ft of draft. How deep is the water? Use a boat pole or a 2X4 and lower it over the side of the boat in a few spots. If your depth gauge is reading 2.5ft I would guess the transducer is about 1.5ft below the water line of the boat giving you about 4ft of water depth. That's cutting it close. You don't want to run in water that shallow and stir up mud the can damage the water pump and clog up the cooling system.

Ok. I found documentation from Sea Ray that states the Draft is 36" with the drive down and 20" with the drive up. I understand that Draft is the distance between the waterline and the lowest point on the boat. But this brings up more questions....

Is the draft provided by Sea Ray based on an empty boat? When I load it with Fuel and passengers the water level is higher on the vessel. I need to account for that somehow.... Which is why I assumed I could use the depth gauge somehow since that will go up and down as the boat is loaded or unloaded.

Is there a way to figure out how much lower the propeller sits from the transducer, that would always tell me how much clearance I actually have, regardless of the weight on board.

I measured the water's depth with a stick and it was approx. 4.5 feet with 2 passengers and 1/4 tank of fuel onboard. The depth gauge was reading 2.5 feet at the time. Can this info be used? Is there a better way?

Thanks!

 

[ttmott]

Ok. I found documentation from Sea Ray that states the Draft is 36" with the drive down and 20" with the drive up. I understand that Draft is the distance between the waterline and the lowest point on the boat. But this brings up more questions....

Is the draft provided by Sea Ray based on an empty boat? When I load it with Fuel and passengers the water level is higher on the vessel. I need to account for that somehow.... Which is why I assumed I could use the depth gauge somehow since that will go up and down as the boat is loaded or unloaded.

Is there a way to figure out how much lower the propeller sits from the transducer, that would always tell me how much clearance I actually have, regardless of the weight on board.

I measured the water's depth with a stick and it was approx. 4.5 feet with 2 passengers and 1/4 tank of fuel onboard. The depth gauge was reading 2.5 feet at the time. Can this info be used? Is there a better way?

Thanks!

Load the boat up then put a mark on the transom at the water line. When the boat is out then measure to the skeg at the lowest trim setting both from the water line and where the transducer is mounted. It's the only way you'll really know.

 

[NJ Gonzo]

Load the boat up then put a mark on the transom at the water line. When the boat is out then measure to the skeg at the lowest trim setting both from the water line and where the transducer is mounted. It's the only way you'll really know.

Thanks. That would work if I had a trailer and could pull the boat out. (Perhaps I can swing by the marina when they pull the boat out in October.).

Is there any way to get this value (or at least get a value reasonably close) while the boat is still in the water? With the lake water getting lower each week I'm starting to get nervous.

As a workaround, can I maneuver in and around the dock at slow speeds with the trim up say at 5 or 7? Or would that not be recommended. That may be the only safe thing to do for a while... (I'm still a relatively new boater so I still have some questions, like this, that may seem basic.)

 

[JimG]

You can maneuver the boat with the drive up (prop still in the water) at slow speeds... should not be a problem.

 

[KrazyKarl]

Slow running in shallow water I keep it trimmed up until it reaches 3' then I shut the engine off & walk it in or until I'm pasted the shallow. I don't like sucking up all the sand & grit into the outdrive.

 

[NJ Gonzo]

So I measured the depth of the water this weekend on a stick, it was about 40-42"
My Onboard gauge read 24" (actually it said' but I converted it to inches for this example)
So that appears to mean that the transducer is mounted 18" below the water line.

SeaRay's Documentation says the Draft is 20" when up and 36" when down. So if I subtract the 18" that leaves 2" clearance when up and 18" when down. Does this sound right?

That would mean if I have the prop trimmed all the way up, I should be "safe" down to 1/2 foot on my dash gauge and once the gauge reads 2 feet or more, I can trim the motor back down to 0. Am I missing something or is it that straight forward.

Thanks everyone for your input!