How to avoid clogging your engine with sand

[Julian]

Says you. Maybe I do not have your expertise but I am an engineer by education and a mechanic by experience. I have owned jet pumps boats and skis since 1990. I have maintained, modified and rebuilt numerous Kawasaki, Yamaha and Rotax axial flow single stage jet pumps. The procedure I use to clear the pump works for me so we just have to agree to disagree.

I'm not saying your approach won't do anything, but it will be WAY MORE EFFECTIVE if you turn off the engines.

 

[Divouneh]

It’s an old threads but still interesting . I have a Scarab 165; my area has lot of shallow areas. I always set idling when we reach 2 ft, last week I had for the first time real contact between hull and stone, most of the time leaves, branches, grass are the main issues: the only solution is to jump on the water to clean up the intake.
In the same time, I have a jet boat to run on shallow area and also for the safety ( we are skiing a lot) .
Yes, I do have some minor repairs to do at the end of the season, no major scratches on my hull …

 

[Tylenator]

So where exactly does that stuff go?

my wife beached the boat the other day on an island - tried to reverse out without pushing off too far, and on enginethrottle got stuck in reverse.

she got it home on the other engine.

I checked both impeller areas, they seem OK. Took boat out, jiggled the stock throttle several times till it let me go back to neutral, then turned that engine fine.

forward works fine both sides but run reverse I’m not sure I’m doing a whole lot other than revving the engine - on either side.

This happened to us the first time we beached our FSH. Even though we had our engines off while we were up in the shallow areas, I guess enough loose sand was washing around from the tide/current that it got all up in the nooks and crannies of the buckets. When I reversed out after pushing the boat into the water, I was stuck in reverse, and I was MOVING TOWARDS ANOTHER BOAT. I had to quickly kill the engines and run to the front and throw the anchor in. The anchor caught it fortunately stopped me feet before coming into contact with the other boat.

We no longer beach the boat.

 

[msavold]

The culprit isn't usually in the buckets themselves AFAIK. Although sometimes it can be inside if it's a bigger rock, the more likely place apparently is at the pivot points on the sides of the buckets, between the nozzle and the bucket "arm". That's where I've had a pebble stuck...

 

[Joatmon]

Good input. I have not experienced grit in the bucket hinge points but did have an issue with the cable sheath rusting.

 

[FSH 210 Sport]

This happened to us the first time we beached our FSH. Even though we had our engines off while we were up in the shallow areas, I guess enough loose sand was washing around from the tide/current that it got all up in the nooks and crannies of the buckets. When I reversed out after pushing the boat into the water, I was stuck in reverse, and I was MOVING TOWARDS ANOTHER BOAT. I had to quickly kill the engines and run to the front and throw the anchor in. The anchor caught it fortunately stopped me feet before coming into contact with the other boat.

We no longer beach the boat.

If you’re in shallow water, 5’ or less and you reverse thrust, the thrust will hit the bottom and blow sand up from the bottom and will get sucked into the jet pump. 3’ is about as shallow as you’d want to be going forward.

 

[Cobra Jet Steering LLC]

If you’re in shallow water, 5’ or less and you reverse thrust, the thrust will hit the bottom and blow sand up from the bottom and will get sucked into the jet pump. 3’ is about as shallow as you’d want to be going forward.

Same thing at the boat ramp I don't know how many times I have said do not back up hard in shallow water or when backing off a trailer And I use car wash soap with the liquid wax in it to flush the engines I also NEVER rev up the engines on the trailer after flushing the engine I just let it sit and idle for 30 seconds then turn it off.
I personally ride in very shallow water all the time and across the grass flats on plane all the time as well , my secret intake grate design works very well to keep weeds out of the intake.
Now back to the reverse maneuver .
I came up with that decades ago and it is very effective to get weed out but not for things wrapped around the drive shaft or lodged in the impeller, I shared that here and someone actually chewed me out on this site because he tried it with people in the water near his boat and he backed into a pile of mangrove seeds floating in the water and got more stuck in the intake, some people you just can't help " I don't drink " so I wondered how many beers he had when he did that. Remember in order to get the boat to go backward the water must be aimed down under the hull and toward the front of the boat, it's physics.
Your intake grate is just in front of the pump housing so when the sand and trash gets shot up from the bottom it is placed directly in the path of the intake grate as the hull moves backward this is captured under the boat hull making it easier for it to get in the pump so the intake sucks it in the pump! The pump also supplies cooling water to the engines and the exhaust , I have seen engine water jackets filled with sand I have also seen water boxed "mufflers" get loaded with sand.
One more point of interest when you get trash in the pump and the boat VIBRATES BADLY " cavitation" do not keep driving as this severe vibration destroys things like the jet pump and the intermediate bearing plus the motor mounts and even the driveshaft.