Hi Kevin I was a bit puzzled by your photo so I thought I would leave it to Jim to reply. Your hand throttle pulls the throttle open. You need a spring which fights this. You therefore need a spring which trys to pull the throttle shut. Your spring needs to be as long as practical. The spring is most important at low RPM (low to no throttle). Therefore your spring needs to be pulling the right amount at idle. This you can test by playing around on dry land watch it as you move the throttle. The spring should do as little extra as possible at high RPM. The only way to balance these two things is to use a long spring. A short spring which provides any force at low rpm will provide massive force at high RPM. The longer the spring the more linear it is. You can force/stretch a spring to make it pull less. And cut it to make it firmer. You do seem to have two springs counteracting each other. The Yamaha hand throttle is 6x0 and there are plenty of them on ebay right now. They are not perfect but they are pretty good. Morse also make good control (ebay morse control) but I am not sure which would be better. Morse controls will work with merc but maybe not Yamaha or Evinrude (as the throttle activation is the opposite). A good spring in the motor may be enough to make your existing cables/control etc right for you. It will certainly make the play a LOT better.
Hi Greg, I did not think anyone would be on at this time of day so I did some editing. I forgot about our time difference. jim
I have two boats with the 6x0. One has a Yamaha engine and I had the normal 704 (or is it 604?) control for it. I disassembeled the stock control to get the kill switch and key switch plus wiring. Mounted them in the dash. It is a bit of a job installing the 6x0 and hard to undo. As it is a concealed mount system you have to bore a large hole. You can then either sit your old merc box on the floor for the electric controls (and go for a test run) or mount the bits or buy a key switch dash panel. I think it is a bit hard and probaby better but not necessary yet. I think a couple of springs will do what you need. Another trick I didn't mention is mixing and matching springs. On one boat I used to have two springs in parallel for half the run and one spring for the other half to get the perfect spring rate.
I have used the two springs in parallel also. Greg, you and I seem to be the only ones that talk about springs. We never collaborated, but we came to all the came conclusions. I would like to get one of those Yamaha controls for my boat. I use the original OMC control and it has a ton of play in it. The thing is that I have a spring set up that works really well and it is like the energizer bunny. It just keeps working. jim
I found out about springs as it was essential to make Perfect Pass to work on my Yamaha. I had made up test parts to fit PP with and had removed them to use them as templates to fabricate proper ones. I also removed the spring and then I couldn't hold low speeds any more. The thottle was painful. Put the spring back and it was great again. So I've used them ever since. I'm not sure that I rave about how good the yamaha control is. It is OK but needs springs. It sounds like your evinrude control with springs is really good also. I think Kevin's Mercury control will be fine as long as springs are setup properly and sheath movement is eliminated. The sheath of the throttle cable should not move. It should not be clamped hard either as this can collapse the sheath and make the cable stick. It should be nicely tied in place. If you move your control and you see the sheath moving then you can see that some of your control is going towards moving the sheath. This is wasted and undesirable. It is especially bad around bends and arcs, these are the worst for soaking up valuable throttle control. If you can see the radius of the cable, the sheath moving wider and narrower around a corner, you will gain great benefits in fixing it.
The Mercury system has a big advantage here in that it pulls for power. The inner cable tends to straighten itself out because it is in tension. I think the inner cable on the push for power set-ups tend to coil up inside the sheath and cause friction and play. On these systems, it is important to use the very highest quality cable available, and be aware that there will be more wear. If the cable behavior is under control, then springs can minimize the mechanical play in my experience. I have this situation under control on our boats. This enables my daughter and me to have a lot of fun together. I give her accurate speed control and she gives us a great show. jim
Here is a diagram of the linkage on a 2.5 liter crankcase injected race motor. I suspect that your motor has something similar. The yellow thing is the big bellcrank I mentioned. The red part is the rod/link that operates the throttle butterfly on the front of the motor. The spring shown is meant to return the throttle/spark linkage when a foot pedal is used instead of the hand throttle. This is a race boat application and the spring is pretty stiff. You could attach a spring there or further down closer to where the control cable is attached. The other end of the spring is attached in the port cylinder head area. I think mine was attached to a sheet metal fitting that went under a head bolt. Now you have me playing with my grandchildren's crayons. :laughing: jim
Thanks Guys. At least I'm on the right track. The springs do counter each other but they may not have the right tension. The throttle arm seemed like a logical place to start as the control cable is directly linked to it. I positioned each spring as to allow for unrestricted movement and attached the ends of each spring to a secure point (the tie-wraps were a temporary connection until I got the rigging right). More testing ahead. The slightly higher idle remains a concern. Cheers, Kevin
The spring that is attached to the oil tank is trying to hold the throttle off idle. Where does the rod that disappears behind the alternator go? jim
Jim, That's the linkage to the control cable. I looked at placing the springs towards the back of the engine where this linkage arm starts, but if my memory serves me correct, it is VERY tight back there. Kevin
