two words- Very inneffecient.
Original Johnson jets were designed for the Millitary to satisfy a contract to get shallow running and Johnson did it as they had the only outboards that could be tuned to run on avgas (another millitary requirement then). There were 2 set ups one for low speed torque for moving around bailey bridges, barges etc etc and one for speed being used for shallow water planing insertion RIB's
It is very hard to make them effecient at varying speeds and loads as they require different impeller designs and therefore impose different torque requirements at different revs so there is no one motor , tune , impeller that suits all situations and in all but it's optimum it will be suseptable to burn out powerheads due to being under or overloaded. Might be a bit different with 4 strokes
A lot are sold in the States and Canada in everglades and lakes where either ice or weed is a problem. These motors still have water pump and intake problems so beware unless the motor is big enough to have overheat alarms if you are running them in mud or weed.
There use to be a small version in Australia for tenders so you could let the kids lose and not worry about them getting chopped up by a prop. It was a Victa lawnmower motor with a vertical shaft a bracket and a jet pump on the bottom. I've owned a couple and they are the lowest cheapest maintainance boat motor I've ever owned. Rebuilds - off to the mower shop!! Thanks Victa
You'll just have to take out a second mortgage for the fuel bill and they can cause grief with a tinny if not set at right depth.
Several aftermarket brands are much more effecient but I guess it depends on your usage and boat style.
Unless you have a specific purpose like running stoney glacial rivers like in New Zealand I wouldn't worry.
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Originally Posted by Blackened
