1968 merc 500

[Iandayen]

My grandfather just gave me a 1968 mercury 500 he had sitting around for 5 years, he had bought it to put into a small boat but never got around to it.

The guy he got it from said it ran but was starting to overheat.

There is writing on the motor that suggests that someone checked compression and all cylinders were at 145. 145 seems a bit high to me I was thinking it should be in the 110ish range, but I'm far from being an expert.

The motor besides being a bit dusty looks rather clean and in good shape, the prop looks good and grandpa said that when he got it the water intake holes near the prop were full of black sand, packed in pretty good, he thinks the guy might have backed into a sand bank and got sand packed in there causing it to overheat.

I will probably replace the impeller also just in case, but what are some common issues or things I should look for tomorrow when i get this on my boat and go to start it with some muffs on.

Also, what is the recommended fuel mixture for this motor?

Anything I should do before I go to start this thing, things that should be checked first so I don't cause any problems?

Edit - This is an electric start with an alternator.

 

[Arkman]

Re: 1968 merc 500

Got any photos? I have a 68' 200, I like those years, they look cool. On mine I replaced the spark plugs and redid the carb. Also changed out the fuel pump diaphragm and gaskets. Now I'm no to the coils, but thats because I didn't have spark, so it might be different story for you.

Keep us updated!! GOOD LUCK!!!

 

[Iandayen]

Re: 1968 merc 500

I'll get pictures tomorrow, have to get batteries for the camera still.

Its a 1960 Sea king Fiberglass Runabout - Title says 13' 6" but registers as a 14' boat.

It currently has a 58 Evinrude lark 35 horse on it, but I want it to go faster, and the 50 horse was free from my grandfather.

My Brother and I will be tearing into it tomorrow, I will get pics and maybe some video.

 

[Iandayen]

Re: 1968 merc 500

Sorry, no pics yet.

My brother and i replaced the Impeller, impeller housing, gaskets, o-rings etc..

Checked the lower gear oil, not milky at all, yay!

put it back together, it went together nice and easy and decided to give it a test run before we did anything else.

Put it in some water in the driveway and got her to crank over and to my surprise it started up.

we were running my old evinrude 25:1 fuel though so she smoked a bit, will dilute it to 50:1 before i put it in the lake tomorrow.

One thing that confuses me a bit though are the controls.

it is a set of mercury controls, a little black lever on the right side of the box and a bigger lever that changes the gears on the right side. (sorry no pictures, my camera took a dump on me)

Now is this the type of control I heard about once where the smaller black lever is the warmup throttle and the actual throttle is built into the gear changing lever?

If so, how exactly does it work, do I just use the black throttle while it warms up for a few minutes until it runs with it all the way back in neutral, then leave it all the way back and use the gear shifting lever for the in motion throttle control?

 

[64tbird]

Re: 1968 merc 500

sounds to me like the black lever charges the dilithium crystals, and the red one engages full warp.

 

[Iandayen]

Re: 1968 merc 500

yeah but is this motor capable of warp 12 or only warp 10?

 

[daveswaves]

Re: 1968 merc 500

Sorry, no pics yet.


One thing that confuses me a bit though are the controls.


If so, how exactly does it work, do I just use the black throttle while it warms up for a few minutes until it runs with it all the way back in neutral, then leave it all the way back and use the gear shifting lever for the in motion throttle control?

YES

 

[Iandayen]

Re: 1968 merc 500

thanks Dave.

Found out on the lake that we didn't do a good job on the impeller the first time around, and that I need to rebuild the fuel pump on this guy.

I started hearing a squealing noise with my Brother (64tbird - the smart*** up there) while testing, and engine started getting hot and smelled like burning rubber/oil So I shut her down and towed it home.

Opened up the lower unit again and we had forgot to put the key in the impeller, and the new housing that came in the kit wasn't sealing right so impeller was spinning on shaft, causing heat, and burning gear oil that was coming from lower unit >.<

We put the old housing back in, used a bit of silicone to help seal it, the impeller wasn't burnt up, just a few rub marks inside, so we put it back in, and remembered to insert the friggin key this time.

Hooked a garden hose up to the water inlet tube that goes into the water pump unit to flush it out and check to see if my water way was clear and realized this motor does not have a tell tale. But we did see water coming from around the spark plugs in the head - got very very nervous for a second until we pulled the plugs and realized that it wasn't coming from in the cylinder, just around the gasket holes by spark plugs - at least i know water is getting up to my power unit now!

Ordered a fuel pump rebuild kit and picked up a new gasket for the waterway area by spark plugs, guy in a boat shop down here sold me both for $14.

Will be working on it on Monday and hopefully I'll have a working camera then too to take some pics for you guys.

Hopefully I can get it running good this week, a few of my in-laws are in town and it's been over 100 degrees for over a week now, a day long trip to the lake and boat rides would be great fun if I can get this puppy going strong =D

 

[Aqualift]

Re: 1968 merc 500

Your motor does have a tell tale. I have two Merc 500's and one is a 1968. My tell-tale is plugged up really bad too. But I cleaned the hose (had a lot of bugs in it) out to the fitting on the bottom of the block and I still get no water. I'm removing the powerhead today, so I can get the exhaust cover plates off. It's probably some sand or debris that collected down there. Have you checked and or cleaned the tell-tale line from the cowl back to the block? Usually that solves the no water problem.

 

[Iandayen]

Re: 1968 merc 500

While replacing the gasket yesterday i did just that, had some mud dauber crap in there.

It seems to be a very small tell tale, on the right hand lower side of the cowl.

I know I was getting water up to my power head because the gasket around the spark plugs was leaking, and I just replaced that yesterday. Going to go pick up my fuel pump kit here in about 15 minutes, put it all back together and lake test it again.

I have a working camera/camcorder now too so I'll try to remember to take some pics and video.