Cam Follower not following enough

[durk187]

I have a 1966 Evinrude 18hp fastwin (18602) and a 14' bass buddy flat-bottom jon boat. <br /><br />I need some ideas on getting a little more out of her. It seems like I can only get the boat 3/4 of the way on plane at WOT. And I think she could be alot more user(and gas)friendly up on plane.<br /><br />I have played with the trim, the prop is running the correct RPM's, and have done a carb rebuild along with the usual basic matinance, ie. plugs.<br /><br />A few questions(bear with me).<br /><br />1. The anti-ventalation plate on my rude' is about 3" below the bottom of my trandsom how much inprovement would I get with it being level?<br /><br />2. I haven't played with the ignition system yet, ie. points and condencer. Could timing and sync. play a big role in proformance?<br /><br />3. Am I just being unreasonable in that a 18hp motor should not put a 14' jon boat on plane.<br /><br />Thanks for all who are kind enough to share ideas.<br /><br />DC

 

[brother chris]

Re: Cam Follower not following enough

Well, I can only offer advice from my past expiriences. As for the anti cavitation plate..on my boat(16' Winner w/ a 55 rude), the cavitation plate is about 1/2" below the transom. It works fantastic. <br />One of the last boats I had a month ago was a 16' K&C thermoglass with a 1978 25hp Johnson on it. It would not go on plane at all and it was a light boat. <br />You might be asking too much out of your motor(in my opinion). But you could also try adjusting your weight in the boat. If you have too much in the rear, or if you are sitting right at the rear, that might affect it too. Even out the weight, or try putting more forward. That MIGHT put you on plane. Didn't work for me though. <br />But good luck, I hope it works. <br />Try raising the motor so the plate is within 1" below the boat. <br />Happy boating...

 

[ob]

Re: Cam Follower not following enough

3 inches below is too much .move motor up and I think you'll notice improvement.

 

[durk187]

Re: Cam Follower not following enough

Thanks for the ideas, I will raise the motor up with a block of wook tommrow and test the setup out. Ill let you know the results.<br /><br />Is there anyone outthere that has a compareable rig that runs the same?

 

[plywoody]

Re: Cam Follower not following enough

If you really are getting the proper RPM's (how did you check it, and how do you know?) then other than raising the engine as others suggested, and distributing weight properly, there is not much you can do.<br /><br />I am assuming, of course, that the bottom of the boat is in decent shape, and there are no big indents or other things that might cause an increase in friction with the water.<br /><br />With a normal load, an 18 should plane a 14 foot light weight flat bottom jon boat relatively easily, if it is set up right and producing full power. I used to have an 18 on a relatively heavy 14 ft wood boat, and it planed that fine. Of course, I was somewhat lighter in those days.

 

[steelespike]

Re: Cam Follower not following enough

If you are average weight and not carrying too much weight you should just about fly.<br /> Had a 15ft plywood runabout with full decks and<br />floors.It was over 6ft wide.would plane easily<br />even with me steering from back deck.It would run<br />an indicated 27 mph under most conditions.<br /> Once managed 24 mph with 5 people aboard though this was a fluke.Start with a service manual.<br /> I would do a compression check be sure points are set right (.020).Be sure carb. is opening all the way and syncro is right.If you are a real load you might have to move some weight forward<br /> If your cav.plate is really 3inches below<br />the bottom youve gat to get it closer.<br />A 1 inch change could give you as much as 3 miles an hour.

 

[durk187]

Re: Cam Follower not following enough

I just noticed something, when playing with the carb linkages when tiller arm is set to WOT. I can take the cam follower and pull it foward another 1/2 inch. I dont think the carb is getting opened up all the way. How would I go about fixing this? New, larger cam follower?<br /><br />I also have a friend who has a 1968 20hp johnson. His cam is a different shape then mine. Mine has a gradule taper to it and his is pretty flat, with a large taper at the end of it. What is the difference between the two.<br /><br />A picture is worth 1000 words.<br />at rest<br />

<br />pulled off<br />

 

[Bear]

Re: Cam Follower not following enough

This guy have the same problem. I had it too. <br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=17;t=018166 <br /><br />A new roller, larger diameter, will fix it.

 

[Outrage 19]

Re: Cam Follower not following enough

A longer push rod between the butterfly arm and roller arm will do it also.

 

[durk187]

Re: Cam Follower not following enough

where can I get one of those?<br /><br />Make my own?

 

[P.V.]

Re: Cam Follower not following enough

The "rule of thumb" is have the ventilation plate level if not slightly (1" or so) above the bottom of the hull. Having the gearcase too far in the water provides more resistance and you don't need that. It also may put up a rooster tail of water, same thing, too much drag!! As far as the carb opening up far enough, put the motor in gear, turn the throttle to wide open and look down into the venturi, is the butterfly horizontal inside the opening? The "extra" movement would just make the butterfly go past "centrer" and actually slow down the flow of air. A different cam, roller or link arm is probably not the problem. Don't screw with it! Check out the butterfly opening.

 

[markjewell]

Re: Cam Follower not following enough

I agree with P.V. about the carb going past center. I have a 1961 18hp fastwin. Carb should just start to open when that "roller" is centered on a timing line on that brass colored throttle control cam that actuates this roller. Move your throttle control back and forth. I think that you will see what I am saying. That brass colored cam plate is also adjustable by loosening the 2 screws that hold it onto the the armature plate.<br />Mark

 

[aeronutt29]

Re: Cam Follower not following enough

My first boat was a 14' fiberglass boat with an 18 HP Evinrude. Not only would it get up on plane, but I skied behind it too! You should be able to get plenty more power out of that motor. <br /><br />How did the compression test turn out?

 

[durk187]

Re: Cam Follower not following enough

MAJOR testing on the water tommrow. I will let you guys know what I find.<br /><br />Yes it dose throw a roster tail, I thought that was uncommon.<br /><br />About the timing marks, I have 2 which one should I center to?

 

[durk187]

Re: Cam Follower not following enough

Update: Leaving for Lake now, raised motor 2" with block of wood. Looked in throat of carb, the butterfly does go past full, but it dosent even get there otherwise. I wrapped tape around the cam follower to see if that improves anything getting the butterfly to open fully and not over-rotate. If it does I will make a perminate fix.<br /><br />DC

 

[durk187]

Re: Cam Follower not following enough

WOW, jeez what a difference , twice the boat it was yesterday, im not kidding. I contribute it mostly to the lower unit raise. The boat hops on plain and I can keep it there with a little more then 1/2 throttle. No more rooster tail anymore either. Top speed at WOT is approx 25. Its a lot louder too, when on plane the exuast port is above water. I also get a little more RPM's out if it. <br /><br />I also played with the trim a little, any higher then 2nd from the bottom and she vents like crazy.<br /><br />Now I need to put a tach on it and see if I am still within RPM limits.<br /><br />A BIG thank you to all who posted ideas on this, once again hats off!<br /><br />DC