Jack Plate

[bm258]

I have gotten to a point where i am going to do some work to my engine (rebuild carbs, water pump, etc.). it is a 1990 Johnson GT 100, and the boat is a 1982 venture bass boat. I want to get a little more performance out of the boat, mostly top end speed. I know the motor needs to be raised a little for the cavitation plate to be even with the bottom of the hull. Also, if i ever decide to chane props i may need to raise or lower the motor. I am somewhat new to jack plates. I was just looking for some ideas on this situation. I have heard that jack plates make the ride more fuel efficient and smother. If anyone has any suggestions or can explain jack plates to me please do so. Any info is helpful.

 

[Dhadley]

Re: Jack Plate

That would be a very good investment with that hull. Jackplates make verticle adjustments very very easy. Especially hydraulic ones -- love to push that button! (Check out www.bobsmachine.com for more info)<br /><br />Setback is also involved. That changes the center of gravity or balance point. Gaining speed is all about efficiency. If you gain efficiency you gain holeshot, top end, fuel economy -- everything.<br /><br />A jackplate opens up a whole world of propellers. Now youll be able to take advantage of the technology built into todays props.

 

[bm258]

Re: Jack Plate

thanks for the advice dhadley!! I had read somewhere that bobsmachine was good. A hydraulic jack is out of my price range. Should I be looking at the 4 in 1 Convertible Jacking Plate. This seems to be the one that will fit my engine. Again, thanks for all of the help.

 

[Dhadley]

Re: Jack Plate

Yep, the convertable is a great piece. You do have a water pressure gauge, right?

 

[Dhadley]

Re: Jack Plate

Oh -- save yourself a bunch of time -- order the bolt kit when you get the plate.

 

[bm258]

Re: Jack Plate

I do not have a water pressure gage. Do I need one for the Jack Plate?

 

[Dhadley]

Re: Jack Plate

Not for the jackplate but one for the engine is recommended. Sorry! Couldnt resist!<br /><br />Seriously, you'll really want one. Get your baseline now and then watch it as you go higher with the plate. With todays props its entirely possible to go so high you lose water and still get the prop to hook up. It may save you from asking about piston part numbers.

 

[bm258]

Re: Jack Plate

dhadley, thanks again for all of the help!!!!!! I am going to order the 4 in 1 convertable plate from bobsmachine. one more question though which position sohuld i use. i am assuming 5 inch with no wedge. I will update when i get the jack installed and running, but it may be a little while. Thanks again for all of your help.

 

[bm258]

Re: Jack Plate

dhadley, one more question. sorry i am sucha a bother, but i am kinda new at jacking plates. how does the CMC Manual Jacking plate compare to the bobsmachine canvertable plate? it seems the CMC would be easier to raise & lower, as well as more percise (motor level) with the 1 bolt. does cmc make a bolt kit like bobsmachine? Thanks again!

 

[Dhadley]

Re: Jack Plate

No bother at all. I like the Bob's because of the convertable deal. The CMC is a good unit and they are also nice folks. I just like the options you have with Bob's. <br /><br />Usually once I get the motor mounted and centered etc on the manual plate I'll mark it and then mark small increments on each side. That way if I change it out in the water I just look at the marks. Real easy.<br /><br />We always do like you mentioned. Start with the 5" setback and no wedge. Then adjust as needed.

 

[bm258]

Re: Jack Plate

dhadley, thanks again for all of the help. This site is great!!!!!!! I think I am giong to order the cmc moder. I am just paranoid i will not get the motor level with the bob's. thanks again for all of the help! I will post the reseult when i get the plate on and set. It will be a while before i get it all done.

 

[Dhadley]

Re: Jack Plate

Actually its real hard to NOT get the motor level. If all 4 bolts line up -- its level. Never been a problem. The only way it wouldnt be level is if the transom is drilled wrong.

 

[bm258]

Re: Jack Plate

reading your's and other post, i think i will go with the bobs. It seems more people here are using bobs that the other thanks again for all of the advicce.

 

[bm258]

Re: Jack Plate

looking at the bobs, i notice it will fit all V-6 models, but can be modified for any model. what type of modification is needed to fit my motor. 1990 Johnson GT 100 hp

 

[Dhadley]

Re: Jack Plate

None. It will fit as produced.