Older Merc opinions wanted

Dave512 · Jan 28, 2004

What do you folks think of a 1979 Merc 70 hp? Was this a good motor year or should it be avoided. I know it is tough to judge or offer an opinion sight unseen, but just need a general opinion on this vintage motor. Assumptions: Low hours < 250 hours, pretty well maintained over 3 owners, little or no corrosion, no accidents or lower unit damage, excellent cold starting. New stator, trigger and power pack. thanks, Dave

Clams Canino · Jan 28, 2004

Re: Older Merc opinions wanted

It's an awsome motor. It's effectively an inline 6 cut in half. And IMHO it's a more stable platform than the inline four of that species. Treat it well and it'll go for years and years. -W

Clams Canino · Jan 28, 2004

Re: Older Merc opinions wanted

Originally posted by Dave512: >> excellent cold starting. The Cods must be smiling on you. One thing about those old inlines is that cold starting isn't for the squeemish. -W

mellowyellow · Jan 29, 2004

Re: Older Merc opinions wanted

uhhhhh... new stator, trigger and p-pack? and he's selling it now? ruh ro! LOL caveat emptor (buyer beware) MY 70' 1150 stator etc. still works great... once a motor goes south, sometimes is hard to correct. what really happened to this motor? I dunno... do u?

andrewkafp · Jan 29, 2004

Re: Older Merc opinions wanted

I have 4 cyl 81 50HP. I asked the same question on iboats way back (2003). The only things they say to watch is 1. Corrosion of water covers. You may end up having to remove the P/Head as bolts break when trying to repair/replace.2. Keep carbs clean, as a lean condition can burn pistons. I will try to connect my posts. 3. Corrosion of wires (in your case some new parts will minimise) But I like my old Merc.. It sounds and runs great for a little fellow and it's made in the good 'Ol U S of A.

http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=29;t=007214 BTW I have followed just about every Merc post on here and there all many Mercs way older that ours that people will still try very hard to fix and keep. Clams is living proof of this....

JasonJ · Jan 30, 2004

Re: Older Merc opinions wanted

I have never had cold starting issues with my old I6s. The only times that I can think of were times I forgot to prime with the bulb, but as long as the bulb is rock hard, they always have started within a few seconds. Maybe I am just lucky?

Clams Canino · Jan 30, 2004

Re: Older Merc opinions wanted

In my opinion, you're lucky. And perhaps in a warmer climate. And no doubt you have the cold starting procedure knocked. Usually if the idle needles are lean enough for good trolling, the things are a bit of a bear cold. As the reeds get older and a little sloppy, this aggrivates it too. Mine cold starts pretty well, but I know the ropes too.

-W

Chinewalker · Jan 30, 2004

Re: Older Merc opinions wanted

One thing I've noticed with old, hard-starting Mercs, is that often the choke linkages have acquired some slop with age. They were fond of using lots of plastic parts in the linkages which can bend, stretch, etc., and if the carb mouth isn't snugly closed off it won't choke enough to cold-start it easily. Just something else to look at.... - Scott

SeaHorse · Feb 4, 2004

Re: Older Merc opinions wanted

I have that motor and it too has an upgraded ignition system. Mine doesn't idle very well because the carbs are only two stage (idle and hi) with no vacuum compensation or "constant velocity" to help when going from idle to main jet. Because of this, you have to make the idle very rich so it won't stall when taking off. Because the idle is so rich, it doesn't idle very smoothly. It does start well. I just rebuilt the wear out parts in the carbs so maybe it will be better this year. Overall, its a great motor. It has the most power I could find under 200 lbs which is all the weight my little boat can carry without the back end going underwater.

JasonJ · Feb 4, 2004

Re: Older Merc opinions wanted

Clams, I am in Northern Idaho, it gets a bit frosty up here. The coldest I have ran them is high 30s. My 1250 starts easier in the fall than it does in a hot summer day, and even then it still starts very quickly. Guess I am lucky..

emckelvy · Feb 4, 2004

Re: Older Merc opinions wanted

Back to the 70...........I really don't think there's a downside to having all new electronics! They're not exactly cheap!! After all we are talking about a 25-yr-old motor here, doesn't time fly!!!! One thing I do fer sur is to take a compression test. If the cylinders are within 5 psi of each other, you've very likely found a good motor. Best if you can run it on a boat (I'm assuming you're looking to purchase this motor ?yes?), but at least you say it starts well. Idle quality is very important, 3's that are getting 'sick' don't idle well at all. Heck, they never idled that great new, but I'm just spoiled with a Tower of Power 6. This should be a very economical motor, but isn't suited for use on heavy hulls. Only about 43 CI displacement and you must prop to be in the hi end of the rpm band. DO NOT lug this motor or you will certainly toast the pistons. Give it a decarbonizing treatment, use premium TCW-3 or better oil, and Mid or Premium grade non-alcohol fuel, and it should give you many years of reliable service. After all, as noted, it IS half of a Tower of Power. LOL. HTH.......ed

DJENAN · Feb 8, 2004

Re: Older Merc opinions wanted

i have a 1979 70 hp merc and after initially having to replace the stator and trigger when i bought it 6 months ago i have not had any problems. The only problem i have is after about 30 seconds to 1 minute of idling it always stalls. I have told by local mechanics that they are one of the worst motors for corrosion though My compression is 145 on 1 and 3 but only 132 on #2. i guess this is ok compression?

Clams Canino · Feb 8, 2004

Re: Older Merc opinions wanted

Ya that's OK compression. A can of Power Tune might be indicated here. The rings get all "coked up" over the years and stick. As for corrosion, they're only 1/2 as tough to get apart as the six.

-W

Mercury140-I6 · Feb 9, 2004

Re: Older Merc opinions wanted

JasonJ. I used to have a 68 Merc 1250. We had the first one sold in the SF Bay Area. It did start faster than my 79 140 does. The 1250 took on the average of 2-5 seconds on the starter to fire up where the 140 takes 5-10. I go to Priest River at least once a year with my boat. Would love to get together and take the boats out. My E-Mail is skier@p2kisp.com http://www.myfishingpictures.com/showphoto.php?photo=13003 Craig

JasonJ · Feb 9, 2004

Re: Older Merc opinions wanted

That'd be cool Mercury. Your boat is a hair nicer than mine, but I won't tell anyone.

Once the water comes up, my boat is in the water all season.

Mercury140-I6 · Feb 9, 2004

Re: Older Merc opinions wanted

JasonJ What do you mean, "Once the water comes up"? How far down do they drop that HUGE lake? I went from Priest River, all the way to Sand Point and then about 1/2 or a little more down the lake before turning back and looking for a marina (Only a 16 gal tank). Wne into this little campgroound's marina and they told me where I could get fuel. Filled up and high tail'd it back to Priest River. I'd love to know about how far that is, but haven't found out yet. Feel free to E-Mail me at skier@p2kisp.com to see when we could do this. Maybe even take them to Priest Lake Criag

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