Dhadley,need advice Johnson 120

[mrtool2u]

First off,thanks for ALL your help in the past,and I think I speak for a lot of people.You have been giving me advice on how to get my boat a bit faster.Will refresh you on the boat,,1989 Spectrum 19 foot aluminum w/1993 Johnson 120 t/t 90 degree v motor.I have tried various props,with varied rpm ranges,some considered in the sweet spot, raised motor 2 holes,cav plate approx 1 1/2 inches above keel of boat,but was getting blowout at upper range of trim. I have seen very little difference in top speed,possibly 1-2 mph max,and not consistent.So I ask you,do you feel that I am a candidate for a jackplate.Another guy on the forums feels that with a riveted hull,I am wasting my time trying to get more speed.Do you honestly feel that a 6 inch setback plate would help me much. At this point,I would be estatic with 3-4 mph.I watched the other day from the bank as my nephew drove by in my boat,and I was amazed at how much boat was still in the water,,,like 15-16 feet it looked like.So I feel I need to get the front end up a bit.I just have very limited knowledge with this kind of stuff,so I need your opinion on this.Thanks for all your help.

 

[mrtool2u]

Re: Dhadley,need advice Johnson 120

I would value anyone elses opinion on this also,,just looking for as much as info before I make the plunge.

 

[walleyehed]

Re: Dhadley,need advice Johnson 120

My 18ft alum deep-V got 6" of set-back, with a 115 in the 3rd hole and some tweaking with props, I gained over 7MPH from where I started, and about 500-600RPM gain with the same prop...Yes, I have a riveted hull as well.<br />If you do a search under gen. outboards, or boats, I don't remember which, type in setback, I think my pics are still there somewhere from last year..If you can't find it, email me at kenneth.sanderson2@verizon.net and I will email the pics to you.<br />p.s. I should add that Dhadley was my coach on this issue as well.

 

[Dhadley]

Re: Dhadley,need advice Johnson 120

First of all look at the bottom. Lay a straight edge on the keel to see how much hook is there. I'm sure the rivits do slow you down but not as much as a hook. <br /><br />Then again maybe the rivits dont slow you down. Boat manufacturers today put a lot of steps and other "gadgets" in the hulls trying to create air under the hull.<br /><br />Hummm......<br /><br />I would suspect that - given a fairly straight hull - some set back could only help. It should change the center of gravity, or piviot point, and get more of the hull up. However, if you have a lot of hook right at the back, like 1/4" or more, it may not be as much help.

 

[mrtool2u]

Re: Dhadley,need advice Johnson 120

What exactly do you need by a hook.When you say hook,i assume the hull rolls up/down near the back,and if so,I assume rolling up is a good thing.,,,,,,,,,,Hey Walleyehed,,,what kind of speeds are you running,,,did you go with a manual jackplate.What kind of prop are you running.I have been really impressed with these OMC aluminum props,,,the difference between them and the Ballistic,,Stiletto was minimal,,,which could change with a setback.

 

[Dhadley]

Re: Dhadley,need advice Johnson 120

Put the straightedge along the bottom from at least 4' forward. The hull will turn down slightly right near the back. Measure how much it turns down. Thats the hook. If the hull turns up its a rocker bottom. I doubt seriously if thats what you have.<br /><br />A string will work too.

 

[walleyehed]

Re: Dhadley,need advice Johnson 120

I was running an OMC Raker that had some tweaking done to it...13.5X18 with some extra cup and a good balance job.<br />Each boat is balanced different and the hull shape may be slightly different as well.<br />As for speed, the best I got was 51 MPH by myself and 6400RPM.