Oump-Jet Outbaord Users?

[fireman2151]

I am a memeber of a Swiftwater rescue Team. We are currently looking
for a replacement for our 25hp outboard prop that is currently mounted
on a Zodiac IRB.

I was interested if anyone could provide their thoughts on the
performance of the pump jet outbard on inflatables. Just for clarification I don't mean the traditional jet drive outbaord but the newer style. Does it
provide enough power comparable to a prop? How does it handle vegitaition and debris? How does it handle accidental strikes of submerged objects i.e.
rocks?

Any comments or thoughts about the motor you could provide would be
greatly appreciated as I haven't been able to find much information on
the peformance of the motor. Thanks in advance,

P.S. dont mean to be a bother but I am posting this in two different threads to reach the most users possible. Thanks.

[BladesRobinson]

Our department used one of the Pump Jet OMC engines for a number of years. We have run several engines and configurations on a Rigid Hulled Inflatable Boat and our primary mission is "surf rescue."

The concept of the Pump Jet is great but my experience was that we "lost" some power; both "top end" and "hole shot." I estimated the power loss to be about 20-25%.

If you are purchasing the 25hp model but can live well with a 20hp engine, then you won't be disappointed with the 25hp Pump Jet. It is certainly a safer engine to operate! The "pump jet" had better acceleration and handling characteristics than the "jet drive" engines (in my opinion). They worked well in aeriated water (breaking surf/sea foam in our area) and it was primarily becasue we needed faster acceleration and top end that we switched back to a conventional propeller with a lower unit shield. We also had some challenges trying to get the Pump Jet lower unit serviced at the local OMC dealer.

We run a 12' RHIB in breaking surf on the east coast of Florida. We are now using a 40hp Yamaha with an electric start. It is fast enough to out run breaking waves and is quick to get on plane inside the surf zone.

Blades Robinson, Marine Rescue FTO
Indian River County (FL) Fire Rescue
LAT 27°39.133'
LON 080°22.261'
ICW Marker 140

[PSDiver1]

Hi Fireman2151-

Blades is right. The power loss is 20-25% for a Jet Drive. I believe if you buy a Jet Drive that is ready to go. What is stated on the motor is its actuall H.P. vs adding a jet pump later to an existing prop unit (switching out the prop).

We use a 14' Zodiac with a 20 Jet Pump. We have found it to be under- powered with use on the Colorado River. They are definately not without issues. They can still get plugged and you can still hurt the impeller. Really depends in what enviroment you are working in. We require our people to understand and be able to repair (shims) on the river.
Just my two cents.

Thanks,

Bo

[BladesRobinson]

They can still get plugged and you can still hurt the impeller.

I believe Bo is referring to a "Jet Drive" and not a "Pump Jet."

A picture of the "Pump Jet" is shown at:
http://actorlando.com/pump-jet-propulsion.htm

A "Jet Drive" is shown at:
http://www.paschmarine.com/info.html

[WMFF12]

We use a Johnson 30 Pump-Jet on our Zodiac. I personally love it. The river where we had our last recovery was so bad, it ate the lower ends out of almost every boat there. (Not sure how good of sailors we were though... perhaps that may be a factor... )Having said that, most were open prop though. I don't think we had any problems out of ours while we were there.

We have discussed different types of propulsion on our next boat, however it hasn't been decided yet.

As far as power, it has enough rump to move our 14' Zodiac across the water quite quickly. I see some of you have to deal with surf & some pretty swift water. It's mainly lakes & rivers here, although it has done well in swift current.