Prop set up?

[brennan]

Guys:

I am looking for some prop advice: Here is the current set up:

1985 Dynatrac bass boat 17 ft
1985 Johnson 115hp w/ 4 blade 12 1/2 x 21 SS prop (don't know manu)

Runs 42 mph GPS with full tournament load at 4800 RPM.

I am concerned about the RPM # as most say this motor should be near 5800 to prevent coking. Also, if it can go a bit faster, that is always nice....

Any suggestions?

Thanks

Brennan

 

[steelespike]

Re: Prop set up?

Assuming a healthy motor a prop change is probably in order.
How is the hole shot?A 5 inch pitch change seems extreme.
But first fine tune your set up especially vertical height and trim.
Then get us the final max rpm and speed

 

[rndn]

Re: Prop set up?

Welcome to the forum!!
You should be running higher rpm's as you suggested. I agree with the above post that 5" drop in pitch seems extreme. Your motor should be able to push the boat with your current prop or at the very most a couple inche drop, not 5 inches. Has your motor always run that low or is this something new? Is your prop all chewed up and in need of repair? Do you have a water logged hull?

 

[bhammer]

Re: Prop set up?

Are you sure the tach is reading correct? Make sure the switch on the back of the tach is set properly for the # of cylinders too.

If that isn't it, there may be more to your problem as my buddy has the same engine and prop and runs much higher.

 

[brennan]

Re: Prop set up?

Thanks for the responses.....
Boat is new to me so I have no idea of past performance.....

I am not sure of the setting on the tach...I'll climb under there next week....Anyone know the settine for a 1985 v4 115 johnson?

The hull may have some water in it....It had some damage when I got it and it was pretty full of water.....I cleaned it out as best I could when I re-glassed it.....

Hole shot is pretty good. It is on plane in less than 8 seconds......

I think that I need to look at the vertical height of the motor....I have read that the fin above the water pump pickup should be near level with the bottom of the hull. True?

Without a water pump gauge, how does one check if the pump is moving water while on plane?

Sorry for the pile of questions....I appreciate the knowledge on this board

Brennan