1975 evinrude prop/transom height

[75evinrude]

The general rules I've studied on this site don't quite light my way. I have a 1990 14'6" Raycraft<br />V bottom bass boat(fiberglass) with an excellent 1975 70HP Evinrude engine. I assume the boat weighs around 800-900 pounds tops. Now, the problems I am running into are planing and top end speed. At WOT I am revved to 6600 rpm and the recommended operating range is below 6 grand, and to complicate things(at least to me) It will only plane if someone is leaning boward for about 15-30 seconds.I am running the factory gear and prop for the engine~the engine was on a 1976 17' trophy tri hull. There arent any markings on the prop regarding diameter and pitch so I must leave it to more experienced to figure me out. Also does the height of the lower unit change the planing characteristics? Hope I didn't ramble to much~~All responses will be deeply appreciated.

 

[75evinrude]

Re: 1975 evinrude prop/transom height

anyone have some good ideas?

 

[javsam]

Re: 1975 evinrude prop/transom height

get some smart tabs for your boat.<br />it is a balancing problem that would be solved by having smart tabs on and forcing the stern up.<br />their sold on iboats.<br />javsam

 

[Dhadley]

Re: 1975 evinrude prop/transom height

Lets start by getting the engine right. Look at the tach and make sure its set on position 6.

 

[Jdeagro]

Re: 1975 evinrude prop/transom height

Since this is not the origional engine, it may not be at the correct height. DHadley can help here with some suggestions. Once you get it as good as possible, then add our Smart Tabs and you will realy have a new boat. I would avoid changing props until you determine the problem. You have performance issues at both ends of the RPM's (planing and top speed).

 

[75evinrude]

Re: 1975 evinrude prop/transom height

What is meant by set the tach to "position 6"?.....I had a guy suggest at work to run my trim in to the second notch up and extend the engine back with a jack plate to bring the nose higher after planing and possibly run more rake. Does this sound like a good direction??~~Will smart tabs compromise my overall speed????When I finish "lining her out", I want loads of topend, but how long I wait for the nose to drop is not a major issue as long as it finally does plane. Y'all hit me back I'm learning here.

 

[cloud ate noobs]

Re: 1975 evinrude prop/transom height

hey some one answer this guy he needs help

 

[wilde1j]

Re: 1975 evinrude prop/transom height

Dhadley already did. Look at the back of the tach and tell if it's set to position 6 or not (should be). DH can help get this right, but it's one step at a time and there's no magic! rayburncrunchy, also let us know where the caviation plate in reference to the hull bottom extended aft to the motor. Is is even above or below and how much? Once you get that right and sure the tach is set right, then DH can mess with stuff like prop pitch, etc.

 

[Indymike]

Re: 1975 evinrude prop/transom height

Listen to Dhadley,<br />Verify what your tach is telling you.

 

[lark2004]

Re: 1975 evinrude prop/transom height

there should be a switch on the back ot the tach, make sure that it is set to "6". This makes sure that the tach is counting the correct number of pulses from the alternator, which in turn gives you an accurate RPM reading.<br /><br />We need this first so that we can see what your max Rev's are. From there we can work on correct engine/boat setup to get the most from the whole package, and to make sure the motor isn't being damaged from trying to turn the wrong size prop.