Twin 1966 Mercury 500's

[ashedd]

I got a new boat and it comes with twin '66 Merc 500's. I saw them run with muffs, they run great, but didn't see much in the way of water circulation. I think what I've read is that these motors won't really pee at idle, just through the prop hub. I got paperwork from 2014 in which they rebuilt the carbs and replaced the impellers. The guy I got the boat from said they run great no problems. Should I replace the impellers after 2 years of very limited use?

Another question..
My right motor has what I would consider a timing belt under proper tension. The left motors timing belt is much more loose, but looks in good shape otherwise. Is there an adjustment for tension? I didn't want to fool with it and through the timing off.

Any idea what kind of amps the outboards charge at? They both have rectifiers.

Left motor requires tremendous effort to tilt, can it be lubed or does it need to come apart?

Thanks

These are my first real Mercury motor, always had OMC's.

 

[merc850]

Once again someone told you something that is not true! {probably told you the reed valves affect the waterpump too} a motor with a good working waterpump will spray a good stream out of the tell-tale, the hole may have something in it push a same size drill into it and gently twist it, if you suspect the pump take the LU off and check for damaged impeller. The tension is not adjustable but you should grease the distributor adapter(2 fittings below belt) to prevent wear. Follow these instructions and you need only one battery; 9amp alternators and a tach for each one is a good idea.

 

[GA_Boater]

Well I only have one 1966 Merc 500. :joyous:

My 500 did not have a tell tale, so I added one. Easy to do. The top of the motor has a plug you replace with an elbow, then run a hose to an already installed outlet on the lower cowl.

I don't trust people selling boats or used cars, I would replace the impellers now and every 2-3 years. My experience is that OEM last longer. And change the lower unit lube - Look for water in the old lube.

The timing belts do stretch and there is no adjustment. Replacement is all you can do and it isn't hard and will not throw the timing off as long as you know where the marks are before disassembling anything. Like Carl Jr. said (LOL - inside joke), grease the magneto fittings. You do have a magneto.

The Merc 500 of this age have 6 amp charging systems. As long as I start the season with a charged battery, it keeps up. If I have any starting problems that wears the battery down, on the charger when I get home. There isn't enough power to charge a flat or worn down battery unless you cruise about 3-4000 RPM for a long time.

On the tilting, I don't have a grease fitting on the tilt tube, but I also have an easy to raise motor. So I haven't been onto that area.

Welcome to the Dark Side - The place to be.

 

[ashedd]

Thanks for all the info. I may switch to LED bulbs to lower the current draw, it already has two batts, Maybe one of the batts can be a deep cycle. I can keep a small charger plugged in when it's moored if I need to. I'm waiting on a new starter since one of them was flaky and finally gave out. I think I'll try to pull start that one and check the pee holes on both, this time with a barrel and not muffs. They both have a hose on the pee hole fittings. Also looks like one of my props had some "work" done to it at some point, The shape of the blades don't quite match the other one, otherwise they are both identical 2 blade props. I'll see how these motors work out this season, the idea of twin bearcats sounds interesting too. I don't like controls that are mounted vertically, so that may change soon. It's a '66 20' Tollycraft cabin cruiser, max recommended HP of 110. I'm thinking the motors may be original to the boat.

 

[merc850]

Don't run deep cycle cycle batteries they take more power to charge than those alt. put out, normal marine starting batteries (not maintenance free) are fine one for each motor both motors should have alternators. One of those props might be cupped to reduce cavitation.You might want to check the magneto(s) point gap too - the cam wick is important.

 

[GA_Boater]

A little warning - If you get into the magneto, be gentle. The prices for parts will knock you on your kiester if something is broken. That's if the parts can be found.

66 Tolly with 66 Mercs - Sounds like an original to me.

If you need a prop, as far as I know, there is only one place to get props because of the number of splines. I don't remember if the place carried 2 bladers for the 500's.

 

[merc850]

Plugs gaskets etc. http://store.oldmercs.com/category_s/1263.htm

 

[ashedd]

So if I do one batt for each motor, how should the batt switch be set(both, 1, 2). And which batt should I get power from for the electrical of the boat? I would think that I could run ships power from the "both" terminal of the switch, but are the motors ok with their alternators being tied together when in the both position? These are all things I've never thought about since it's my first twin engine setup.

Later today I'm going to go to my moored boat and fire up the 175 blackmax, that thing is like a space ship power plant compared to these 500's

 

[GA_Boater]

Does the boat have much of an electrical load?

Battery set up questions like this might be best asked in the Electrical section, ash.

 

[ashedd]

Does the boat have much of an electrical load?

Battery set up questions like this might be best asked in the Electrical section, ash.

no not much of a load currently. Nav lights, fish finder(that I would only use to check depth), vhf, standard horn, wiper, bilge. One interior light.