I Need A Lot of Help

[mulliganmagic]

I have a few problems for my boat that I need advice for. First of all the boat is a 1975 15'6" K-Craft tri-hull bass boat. I am in the process of getting a 1977 70hp mercury outboard for it. First of all the motor is on another boat and I am going to switch it to mine. I have a lift type device to lift the motor with, but I'm not sure how to secure a chain or something to the motor so that I can safely lift it off of the boat. Next problem is a tachometer. The boat does not have a tach on it, but I have a mercury tach to put on it. The prop that is on the motor right now looks like it's smaller than a 13 pitch so I'll need to watch the rpms so that I'm not going to hurt the motor. The question is how do I hook a tach to the motor. I'm not quite sure about the wiring part of it. Also if anyone has any prop reccomendations please don't be shy because I need all the help I can get. Right now I have access to a 13 pitch and a 19 pitch prop that I could test on this motor but I just want to be careful and make it last a long time. I think that the rpm range for this motor should be about 5000-5500 please correct me if I am wrong. I think those are all of my problems and any help given is appriciated.

 

[agrazela]

Re: I Need A Lot of Help

MulliganMagic,<br /><br />I have a 78 70hp on a 15' trihull. I use a 10-3/8" by 12 pitch prop and this gives me about 5200 rpm. You are right, 5000-5500 is the correct range. I highly doubt that this small gearcase motor could turn a 19-pitch prop in the right rpm range unless it was on a 12' aluminum boat!<br /><br />You can get a lifting ring that screws into the middle of the flywheel. Your dealer may have one, or you can find them on e-bay. There is no other safe way to lift the motor.<br /><br />If you have a Merc control box, the tach hooks to the grey wire at the front of the box. If you are going straight from the engine to the tach, hook into the rectifier where the two yellow wires are attached.

 

[mulliganmagic]

Re: I Need A Lot of Help

Thanks agrazela. I ended up getting the motor on the boat this morning by hand. We had three guys and just lifted it on there. Also, I found out that the motor has a 13 pitch prop on it and I will hook up a tach before I do my frist trial run. The key that came with the motor was broken so I had to order 2 new keys from the dealer after I got it and before I start it. I still have to hook up the controls, gas, batteries, and do a few other things before I can try it out. I do have a mercury control box, but I'm not sure that I have the grey wire you're talking about. Is there a diagram or picture that I could look at on the internet? There are only three things coming out of my control box the two cables for gear and gas and the large round cable for the ignition.

 

[Bondo]

Re: I Need A Lot of Help

There Should be a little rubber plug receptacle in the Front of your control box,.. about 3/4" in diameter........<br />That's where a Tach. plugs into a Mercury......

 

[mulliganmagic]

Re: I Need A Lot of Help

Really? I saw that on the controls yesterday but the guy that helped me take the motor off of the old boat said that was the idle adjustment. I'll look into that, but I haven't looked at my tach to see what kind of wires or plug it has on the end. If it doesn't then I'll have to wire it to the motor right? But if it goes into the controls then it will plug into it not wire correct? I've never hooked up a motor or controls or anything so please bear with me.

 

[Bondo]

Re: I Need A Lot of Help

It should be a 3 wire fitting......Power,.. Signal,.. Ground......<br />Merc. will sell you the wiring adapter(a plug with 3 wires in it) that'll get you to the Tach wiring........

 

[mulliganmagic]

Re: I Need A Lot of Help

agrazela,<br /><br />I just found out that I have to replace the rectifier. It was old and I broke a thread off of it trying to remove a wire. But I would like to know how to wire the tachometer straight to this rectifier since I'm replacing this little gizmo any way. My tachometer has three places for wires and I think that it's a mid 80s quicksilver tach.