25hp evinrude sportster 73 slipping? mounting issue , or possible needs new prop?

[sydney_ike]

hey i have finished installing this motor onto a 14 foot fibreglass boat, it cruises fine how ever when throttle opens it gains no speed as engine is revving its like no thrust is being gained at all i have an imagine down below of current config please help

 

[steelespike]

Re: 25hp evinrude sportster 73 slipping? mounting issue , or possible needs new prop?

Remove the prop and draw a waterproof line across the hub and body, test run and check if the line is broken.
If broken it's time for a new prop.

 

[westcoaster90]

Re: 25hp evinrude sportster 73 slipping? mounting issue , or possible needs new prop?

I have this exact engine sitting on the stand that I just did a tune up on. I have not removed the prop on this one yet but a lot of the others I have worked on have had a shear pin rather then a rubber hub. the shear pin either works or it doesn't. the engine would not even push the boat at idle if the pin was sheared. if it does in fact have a rubber hub you could need a new prop. your cavitation plate could be to high above the lower part of the transom and if you trim is set to high it would definitely make that to much rev no go situation worse. I like to have these old johnyrudes cavitation plate an inch below the lower part of the transom otherwise they cavitate at high trim.

 

[sydney_ike]

Re: 25hp evinrude sportster 73 slipping? mounting issue , or possible needs new prop?

cheers for info how ever i ran into other problems whilst changing gearbox oil water was like yoghurt so off came the box for a seal change how ever i have not yet cut the transom on boat! inspected prop it is a shear pin also! that concludes the prop of causing thrust problems it is how ever sitting abit to high