What depth is safe for a stern drive 16ft to 18ft boat?

[MotorMan101]

I am new to boating and live by a river that has a depth of 4 to 7ft. I am looking for a boat and in my area stern drives are main thing in my budget but how deep do they need and what precautions would you take running one on a river?

 

[QBhoy]

I’d say the average depth of water they draw would be about 2.5ft but obviously will squat deeper again with passengers onboard and also when under way at a certain speed when the bow lifts.
Some will draw more water than that too. My 18ft Campion with its heavy hull and v8 engine will draw just over 3ft with the drive down, without anyone in her.
The above is referring to the boat with the drive down. You won’t want to run her for too long with the drive raised above a certain angle really. The UJ will get wrecked.

 

[JASinIL2006]

As @QBhoy says, 2.5‘ to 3.5’ at no wake speed. At planing speed, you can get by on less water, but only if you know there are no obstructions under the surface. We used to use a launch on the Mississippi where there was a chute that was only about 18 inches deep, but you had to be up on plane to be able to make it through that part of the chute without dragging the outdrive.

 

[Scott Danforth]

growing up, we had outboards. hitting floaters and deadheads in the river was common. there was also a submerged rock island that was 60 feet across, and only 4" below the surface. reading the depth finder kept you in the needed depth, however sometimes the prop or lower unit got damaged.

switching from outboards to stern drives, the draft was a bit more, the boats a bit deeper. so the skeg and prop were a bit further below the water line....however as indicated above, not hitting obstacles and running agound are the primary concerns.

watch your depth and know your water. on a river, stationary objects are easy to mark, however the transitory submerged objects are always a concern.... logs, sunken boats, etc.

depth finder transducer on my current boat is mounted 2.2 feet above the skeg and 1 foot below the static water line. I stay in the 4' plus area on the charts. when the alarm on the depth finder reads 2.5', I am starting to shine the props.

my old 16 -19 foot boats were about 1.5 feet from transducer to skeg,

for the hole shot, you will need about 4-5 feet of depth

 

[tpenfield]

I/O boats require about 1 foot of extra depth than an OB, since you can tilt an OB to a greater extent when in shallow water. Even with an I/O, you can run slowly (idle speed) in shallow water.

As mentioned, it is going to be the stuff that you cannot easily see hiding below the surface. In those situations, probably not much difference in the type of propulsion. Any incidents will probably break the bank $$$$

 

[JimS123]

If your local depth is 4-7' don't even think about an I/O. If that's all you can afford, wait until you have enough for an OB. The money you end up spending on repairs will most likely exceed the cost of the OB.

 

[flashback]

I don't know anything about them but maybe a jet drive would serve better.

 

[airshot]

Three foot of water MIN...nothing less, even then you water intake will probably suck up lots of silt and mud which will wear the Water pump prematurely. Very risky at water under 4' deep !!

 

[dwco5051]

Knowing what river could help. Are you planing on pleasure boating, fishing, or even water sports? Are there charts, aids to navigation or do you just have to learn it through experience. I can think of 3 rivers right now that I have boated on close to home with similar depths and they are all different in the ability to navigate without grounding. Go to a launch on a busy day and see what most other boaters are running and talk to a few with your question. Sometimes the best advice comes from local knowledge.

 

[Scott Danforth]

If your local depth is 4-7' don't even think about an I/O. If that's all you can afford, wait until you have enough for an OB. The money you end up spending on repairs will most likely exceed the cost of the OB.

960 acre lake my bud lives on is all under 7 feet (except a very small area by a spring. Must be 200 I/O boats on it