Strange motor height problem???

[mattandmelissa]

I have got a 1993 kingfisher bass boat that is 20' with a 1991 175 evinrude loop charged. I can't seem to get the speed I think it should have I am running at 6000' running a 20 pitch raker I can get 40mph. I have a detwiler 8" jackplate If I raise the motor I loose speed the boat seems like the bow is to far down in the water like I need to have more bow lift. Engine rpm's are 5000rpm with the raker I have tried a 23 pitch renegade and a 21 pitch sst they all do the same thing my motor when it is down all the way prop shaft is around 5 inches below the boat. Is it possible that the motor needs to be lower. Or do I need a better prop my raker has been repaired by propco the renegade is new the sst I have no idea. I tried a 23 pitch tropy and could not plane it would rev to 5000 stand on its tail and never plane sent it off to be rehubbed and same thing. I am at a lose but I know if I could get the bow up It would be way faster it is cutting the water way forward on the bow. Anyone got any Ideas?? The motor is in good shape I have tried two different motors of the same kind and both are almost Identical in performance.

 

[steelespike]

Re: Strange motor height problem???

If you can't get the bow up check the bottom for a hook.A concave area just ahead of the transom doesn't take much to pull the bow down.
Where is the antivent plate in relation to the bottom.Is the trim moving all the way out.can you trim all the way out without venting?

 

[mattandmelissa]

Re: Strange motor height problem???

Thanks for the reply steelspike yes I can trim all the way out to way past what my gauge say's I should? The only time the prop looses bite is if I use the turbo prop or have the jack plate up and not be trimmed under far enough but after i get on plane (which I can not do with the turbo) it will never loose bite. There is a slight dish in the hull next to the transom is this what you mean by hook? I had said I tried a trophy prop but I meant turbo prop. I will have to check where the cavitation plate is exactly but I am pretty sure it is a couple of inches above the bottom of the boat.

 

[steelespike]

Re: Strange motor height problem???

That dish could be your problem.Depends if its designed to tame flightyness or a distored bottom.You might check with a straight edge.Depends how large and how deep.And it would be uniform.

 

[mattandmelissa]

Re: Strange motor height problem???

Steelspike with a 4' straight edge it is dished about 3/16 to a 1/4" about 10 inches from the back of the boat? I don't think it is damage cause the hull is in really good condition and it appears to be made this way. Is there anything I can do to make it better??

 

[mattandmelissa]

Re: Strange motor height problem???

Steelespike can a prop reworked give me the lift I need?