Performance Question (dhadley & others)

[skyguy59]

Heres the scoop; 72 Carlson CV 16 72 100 HP Johnson OEM T&T conversion done. X dimension is approx 3/4" Engine mounted in 2nd hole from top<br />OMC 13 1/2 X 20 Raker Prop. 5200 RPM @ WOT but the boat starts getting squirrley in the back end (bouncing from side to side) before I can finish trimming the engine. It might make 5400 @ WOT if I could trim it out. Prop never ventilates. Temp runs normal. (dont have a WP gauge yet, thats next)Shows right at 46 GPS 52 on speedo. Me alone in the boat so weight is off center. Where do I go from here and what can I do to stop the rocking from side to side? Any suggestions.<br /><br />Russ In Texas

 

[LubeDude]

Re: Performance Question (dhadley & others)

Originally posted by skyguy59:<br /> the boat starts getting squirrley in the back end (bouncing from side to side) before I can finish trimming the engine.

Thats called "Chinewalk". In very fast boats, its quite dangerous. It usually can be taken care of by raising the engine.

 

[skyguy59]

Re: Performance Question (dhadley & others)

Thanks LubeDude. I did a search on Chinewalk and I'm not sure I understand how engine height affects it.Would you suggest rasing the engine one hole and test again? How much RPM should I expect to gain from one hole? I looked at the smart tabs but I would like to save that for last resort.<br /><br />Thanks Again<br /><br />Russ In Texas

 

[LubeDude]

Re: Performance Question (dhadley & others)

What happens when the engine is a bit too high on some boats is that when you begin to trim out, the boat rocks from side to side because the engine is trying to lift the boat out of the water and it has to fall from side to side. (One side hits the water then it bumps to the other side and back and forth. It can get "VERY" violent with some boats at high speed) Actually been known to through people out. Raising the engine allows the boat to ride deeper in the water so it doesn do it.<br /><br />Yes, one hole at a time, and you will get around a 1-200 RPM rise at WOT.

 

[WillyBWright]

Re: Performance Question (dhadley & others)

I put a newer 115 60* Johnson on a boat like that. It had a 120 before and the 115 walked all over it. The customer was convinced that his porpoising was caused by the new motor. Well, in a way it was. The boat went at least 5mph faster with it. But it wasn't the motor's fault, it was the hydrodynamics of the hull. I had an incredibly difficult time convincing him that trim tabs would help. He finally let me and it stopped the porpoising and allowed the motor to be adjusted to the proper trim for the best performance. That package didn't have a chine-walking problem tho. It just porpoised real bad as you started getting the motor to the optimun trim angle. Too little bow weight. Tabs kept the bow down. They'd probably add a bit of side-to-side stability as well.<br /><br />One strange thing I've definately noticed. 4-blade props seem to cause much less of a chine walk than 3-blades for some reason.

 

[Scaaty]

Re: Performance Question (dhadley & others)

From what I can remember about those old Carlson's, it was quite a deep V, and large "Pad" it rode on. Ride okay with two people? Actually, you need MORE horsepower to get it riding on the "pad", trim switch mounted on the wheel, foot throttle, jack up the motor and get less water drag. Lots of back and forth cranking on the wheel. FUN.

 

[Dhadley]

Re: Performance Question (dhadley & others)

I dont believe the old CV16 had a pad. If I remember correctly it was the old "round" V and thats part of the problem. The faster you go the less wetted surface you have and the boat "hunts" for a surface to ride on. Whether its the "V" or pad or gearcase. The round V wasnt very stable and many things will influence the area that its trying to ride on. <br /><br />Raising the motor does a couple of things. It reduces drag first. There is a point that when the boat is hunting for that "ride point" the gearcase will create enough drag that it trys to change that point or area. Basically it tries to ride on the gearcase but its too deep in the water to ride on the bottom of the case. <br /><br />Once you raise the gearcase it can ride on the bottom of it and will help stabilize the hull. <br /><br />Props have a tremendous effect on ride. Props will have bow lift, stern lift, overall lift or no lift. That again helps the hull decide where it wants to ride.<br /><br />Then you have to look at the hook in the hull. Hook helps get the boat on plane but is always trying to push the bow down. As you go faster, less and less of the hull is in the water. When the back part of the hull contacts the water the hook will try to push the bow back down. Then the prop tries to pick it back up. <br /><br />Basically you have quite a balancing act going on.

 

[skyguy59]

Re: Performance Question (dhadley & others)

As usual DH is right on about the hull shape. Did some measuring and it looks like I can go up one hole and have the AV plate about 1 & 1/2 inches above the bottom and the water intakes will still be just below the bottom of the boat.<br />I will try to do that tomorrow but the weather is forcasting 20+ MPH winds for the weekend so I don't know if I will get to try it or not. Thanbks for everybody's input, I'll let you know when I try it.<br /><br />Russ In Texas

 

[Dhadley]

Re: Performance Question (dhadley & others)

Sounds good. The Raker will hook up even at the top setting as long as someone hasnt reworked it. Then it may or may not. Watch the water pressure. (HINT, HINT)

 

[Jdeagro]

Re: Performance Question (dhadley & others)

I hate ti think that ?Smart Tabs will be the last resort, but you are getting good advise. I agree with what these boys have said, and would like to add on more bit. If you use Smart Tabs, the chine walking will go way, but the boat (stern) will likely ride higher as well because the tabs (even when retracted) provide some additonal lift.<br /><br />If you raise the engine and the chine walking is not eliminated, and then add Smart Tabs, you should make sure your not too high.

 

[phatmanmike]

Re: Performance Question (dhadley & others)

If you raise the engine and the chine walking is not eliminated, and then add Smart Tabs

or ANY brand of tabs, but since nautiJohn is the president of NAUTICUS, inc, he wouldnt make any money telling you to add some bennets, would he.

 

[phatmanmike]

Re: Performance Question (dhadley & others)

If you raise the engine and the chine walking is not eliminated, and then add Smart Tabs

or ANY brand of tabs, but since nautiJohn is the president of NAUTICUS, inc, he wouldnt make any money telling you to add some bennets, would he.<br /><br />and this is an exact quote from the user agreement:<br />Please note that advertisements, chain letters, pyramid schemes, and solicitations are inappropriate on this BB"

 

[skyguy59]

Re: Performance Question (dhadley & others)

Phatmanmike, I must disagree. Considering the fact that I mentioned his Smart Tabs FIRST, by brand name,and long before nautijohn posted I would say he was well within his right to post the information he did and especially the manner in which he did. He gave an opinion that was useful and directed toward the question I asked. Your post on the other hand contributed positively nothing to the thread.<br /><br />Russ In Texas

 

[Jdeagro]

Re: Performance Question (dhadley & others)

Boys; <br />Lets not get into debate that is not constructive. The reason I posted that answer was to let Skyguy know that the boat could run higher at the stern with Smart Tabs and if he was at the threshold (water pick up for example) it may go over the edge, and he may need to drop the engine again. Just trying to avoid engine problems.<br /><br />I understand that some of you have viewed my answers as a sales pitch with exaggerated claims. As a relatively new product there are few people that understand the system, therefore it is up to us to make sure that inaccurate information is not posted as fact. <br /><br />If you have "first hand experience" that is different than what I post, please let me know as this is not only valuable to others but to us as the manufacturer. If product changes or warnings need to be made then we need to know. Regardless of all the testing, we can not test every boat or situation, therefore we need to listen.