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Author Topic:   OMC Three-Cylinder 70-HP Motor
BlackMax posted 03-19-2006 05:26 PM ET (US)   Profile for BlackMax  
I have a chance to join the Whaler community, and the 1974 Whaler comes with twin Evinrude 70 HP, 1974. My other boats have always been Mercury powered.

The Whaler and engines are totally fresh water use from Northern Wisconsin, and neither the boat nor engines have been used since summer of 1978. Seller tells me the engines have 5 short summers of use, mostly Lake Michigan salmon trolling, about 200 hrs on them total. They are all original, and the boat has been stored in a heated building for the last 27 years. Boat is all original, mint, no bottom paint. He says they have been started up and run on muffs every Spring.

What could I expect from an old pair of engines like this? I have not yet seen them, but he says they look factory new, no corrosion, nothing. Besides impeller replacement, would they be in need of a lot of work, such as carb tear down, head gasket replacement, new seals, etc? Any idea what a pair of classic engines like this would be worth? They are pre-mix. Are parts still available? What should I specifically be looking for as far as potential problems or warning signs?

Any comments appreciated. This seems to be rig lost in time.

JBCornwell posted 03-19-2006 05:42 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Howdy, Max.

The OMC triple loopers, first introduced as a 55hp in the late 60s, were years ahead of the industry in technology and engineering. The 70hp versions were most popular and variations were made up until very recently. It wouldn't be unreasonable to call that a 50 year run. Not common for a mid range engine.

I have owned and used three "JohnnyRude" 70s and all were excellent engines. It sounds like the engines you are contemplating have been very well cared for and would have many years of good service yet to deliver.

Red sky at night. . .

fairdeal2u posted 03-19-2006 06:40 PM ET (US)     Profile for fairdeal2u  Send Email to fairdeal2u     

I ran a 1987 70 vro 70 hp omc for 15 years. Put about 1,000 hours on it. In all those years, all it needed was one powerpack and the regular maintenance. IT should go another 1000 hours easily. Great
technology. As long as there isn't much corrosion. They should run fine for you.

Binkie posted 03-19-2006 07:19 PM ET (US)     Profile for Binkie  Send Email to Binkie     
Wow, what a find. Post some pics, after you buy it. Those OMC triples are a great motor. The only complaint I`ve ever heard is they are a bit thirsty. the OMC triple is used in outboard racing, and with a racing lower unit will run 80+mph on a hydro.
djahncke posted 03-19-2006 07:24 PM ET (US)     Profile for djahncke  Send Email to djahncke     

I have been running a 1978 70HP Evinrude on the back of of my 15 Sport since I bought it 27 years ago. The motor has been very reliable and made me a true OMC fan.


RJG posted 03-19-2006 08:05 PM ET (US)     Profile for RJG  Send Email to RJG     
I have been around them for 30 years and aways thought they were one of the best engines ever built.
fourdfish posted 03-19-2006 08:36 PM ET (US)     Profile for fourdfish  Send Email to fourdfish     
Sounds like a great find! Sounds like something I have been looking for! How about some pics. Those engines should serve you well!
jimh posted 03-19-2006 11:42 PM ET (US)     Profile for jimh  Send Email to jimh     
The three-cylinder OMC 70-HP outboard must have been a great motor. Yamaha made an exact copy of it when they brought out their three-cylinder 70-HP motor.
Peter posted 03-20-2006 08:20 AM ET (US)     Profile for Peter  Send Email to Peter     
The Yamaha 70 is not and has never been an "exact" copy of the OMC 3-cylinder. Actually, if you look at them side-by-side with the cowls off of each you would see that they are quite a bit different.

Specification wise, the latest version of the OMC 70 displaced 920 cc with a bore of 81mm and a stroke of 59.4 mm. It turned the propeller through a 2.42:1 reduction gearcase.

In contrast, the Yamaha 70, which is still in production, displaces 849 cc with a bore of 72mm and a stroke of 69.5 mm. It turns its propeller through a 2.33:1 reduction gearcase.

jimh posted 03-20-2006 08:37 AM ET (US)     Profile for jimh  Send Email to jimh     
The cylinder head castings look identical. My Evinrude dealer told me that OMC took legal action against Yamaha because the designs were so similar. Maybe that's an old war story.
nnylip posted 03-20-2006 09:57 AM ET (US)     Profile for nnylip  Send Email to nnylip     
I have a 91 version of the engine and it has rarely run right. A matter of fact, I am going to bring it in this week to have the thing tweaked (again).
To be specific, it has never run right at low speed, it has always run well at WOT or medium throttle. Part of it may be how it is used. It is kept at a weekend house and gets used during the season every week or every other week. The thing starts up in a nasty way with lots of smoke etc. It is largely used to pull around tubers (what a poor life for an engine) and the thing conks out after a few idles and starts.
The mechanic occasionally blames the VRO pump saying the engine oil drys up during the week of no use with the sun baking on it.
If any one has any suggestion or a link on how to make run better it would be greatly appreciated.
sosmerc posted 03-20-2006 11:20 AM ET (US)     Profile for sosmerc  Send Email to sosmerc     
As one might guess from my username, I'm a Merc guy. But the early 3 cylinder OMC engines were an outstanding motor. I can see why Yamaha got alot of ideas from it. OMC really started "messing" with these engines about the time they introduced VRO....and they went downhill from there in my opinion. They bumped the cubic inches a bit and went to a lost foam casting (all good things), but then they also started making carb changes and plumbing changes I think their quality control was lacking. Heck, even the paint wouldn't stay on OMC engines after 1983.
But the early ones were sweet motors!
elaelap posted 03-20-2006 12:49 PM ET (US)     Profile for elaelap  Send Email to elaelap     
I finally got out yesterday for a couple of hours in 'Strike3', the 1978 Revenge 21 owned jointly by me and CW members Matt/placerville and Warren/WT. The boat has twin Johnson VRO 70s, and it's interesting to hear this chatter about those new-to-me motors. We'll never know how many hours our motors have (they're 1991s), but they seem to be doing just fine so far, and that Revenge moves right along when we get on the gas a little. The boat planes easily on only one motor, even with the other dragging in the water rather than tilted up, and the mid-range acceleration is impressive, especially compared with my classic Outrage 18/Yamaha 115 four stroke EFI combination, which is somewhat sluggish between maybe 4200-5000 rpm. The 70s do seem to be thirsty; of course I'm spoiled by the incredible fuel economy of my 115 4/s. Anyway, thanks for the info and opinions about these motors, guys.


BlackMax posted 03-20-2006 02:21 PM ET (US)     Profile for BlackMax    
Thank you for your comments. It appears as though these are fine running engines. Could I expect them to be equal to one of today's 60 or 65HP engines on prop HP?

But the question I have, the last paragraph in my original post, still is unanswered. Can I just mix up some 50 to 1 fuel, launch the boat and start using it, or are there things should be looked into after 27 years of no use. I'd really hate to get blindsided with $2000 worth of engine work becasue of the no use situation.

Peter posted 03-20-2006 02:58 PM ET (US)     Profile for Peter  Send Email to Peter     
I think I would approach them as new motors using a break-in fuel mixture.

In addition to replacement of the rubber water pump impeller, I'd be inclined to replace the rubber fuel pump diaphragm on each motor and inspect the internal rubber fuel lines for any deterioration and replace as needed.

fairdeal2u posted 03-20-2006 03:04 PM ET (US)     Profile for fairdeal2u  Send Email to fairdeal2u     
If you wanted to be safe. You could take the plugs out and spray some extra rich fuel mix or get some lubrication onto the surfaces inside. Maybe turn the motor over without plugs in to ensure that it is well lubricated on the
crankshaft and internal surfaces.
JBCornwell posted 03-20-2006 06:25 PM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Gaskets can dry out over time, Max.

I suggest overhaul of the carbs and replacement of the bypass cover gaskets.

Red sky at night. . .

Teak Oil posted 03-20-2006 06:29 PM ET (US)     Profile for Teak Oil  Send Email to Teak Oil     
I would spend a few hundred on the carbs myself, the seals and diaphragms are 32 years old after all. Have the engines checked for dried out gaskets and swap the fuel pumps as suggested above.

Yeah, you could probably run them as is, but for a few hundred bucks you can be sure your perfect vintage engines are up to snuff and wont be leaning out a cylinder any time soon.

Definitely due the water pumps too.

Buckda posted 03-20-2006 06:33 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Black Max -
Sounds like a great deal. What model Whaler are they on?

Re: Getting them started again:

Remember, plastic and rubber deteriorate with age and heat.

I'd approach the restarting of these motors with a little caution rather than just the cavalier "start them and go" mentality.

First, inspect the hoses and any plastic hoses on the powerheads. Pinch them to figure out how pliable they are, and give a gentle pull on them to make sure they're secured to the powerhead plumbing appropriately.

I'd replace the fuel delivery hoses right away, including the primer bulb. Buy BRP replacements, not the cheap tempo stuff.

Pull the props and check lube the prop shaft.

Replace the lower unit gear oil and the gasket around the drain plug.

Have the carbs rebuilt, and replace the on-the-powerhead fuel filter, if equipped.

Spray the electrical connections with anti-corrosion spray, and spray all of the hoses with a silicone lubricant.

Regrease the throttle and shift cable using BRP's Triple Guard Grease or equivalent.

Take your time...they're old engines, but a few hundred bucks and some gentle work on your part will make sure they run like new.

Plan on purchasing new spark plugs once you've done the break-in scenario.

Mix up a special batch of gasoline in 6 gallon tanks and run these through the motors for the first few hours of operation. I'd go with a heavy mixture of oil as others have specified...much like the break-in procedures. Also, for the next few tanks of gas, use Carbon Guard or equivalent fuel additives. I also like to mix a little Marvel Mystery Oil in my gasoline on older two strokes (in addition to the TC-W3 oil).

Have your dealer inspect the thermostats and check the compression when he changes the rubber hoses and rebuilds the carbs.

This will cost about $300 per engine or so. Last summer, my dad gave me the old 1972 Johnson that I learned to boat with. It hadn't been run in 8-10 years. I had the dealer inspect it, rebuild the carbs, etc. (the hoses didn't need it because dad opened the cowling every year and sprayed them down with silicone spray.) it cost me about $275 and started on the first pull.

Also have your dealer, or you if you're handy, replace the water impeller yourself...and I totally agree with Peter, inspect the fuel pump diaphram and replace it - the rubber they used in 1978 was not designed to handle the ethanol content in today's fuels.

I'd spray fogging oil in the cylinders, directly through the spark plug holes, and then turn the flywheel by hand a few times and re-apply the fogging oil and turn it over a few more times by hand.

When you start the motors, let them 8 minutes at least so that they are at full operating temperature, then pull the cowlings and make sure everything is working leaks, etc.

Once you've gone through all of that without any problems, you should be set for years of operation. The 70 was a great motor for OMC. The above recommendations are only because it hasn't really been used in 28 years.


Peter posted 03-20-2006 06:57 PM ET (US)     Profile for Peter  Send Email to Peter     
While we are spending your money on parts and labor, I would also consider running a can of Engine Tuner through each motor, probably after they've gone through the initial rebreak-in procedure.
Buckda posted 03-20-2006 08:19 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Peter -

Spend now or later...his choice.

That is what I would do (and count as part of the purchase cost) if I bought a 31 year old engine that hadn't been run properly in 28 years. With an engine that old, the "opportunity cost" to purchase it should be nil. Spending even $1,000 additional up front to have both motors ready to work is worth every cent, in my opinion. If proper precautions are taken and they are brought back and ready to go (and then meticulously maintained), they should last for about 2-4 thousand with only 250 hours on them, they've got a lot of life yet.

My prediction is that he'll get sick of pre-mixing before teh engines decide to die on him!


Sal DiMercurio posted 03-20-2006 10:06 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Absolutly excellent recommendations in the above posts.
Especially rebuilding the carbs because if they aren't up to par your gonna lean out a cylinder & score it & thats about a $3,500 boo boo.
Absolutly do a de-carb treatment with Bombardiers [ Johnson Evinrude dealer ] Engine Tuner, follow the dirctions on the can.
My dad had the exact same engine on his 18' Dorset & he still used it when he was 88 years old, fishing at least 5 days a week during the fall striper run.
He used the cheapest gas but the best oil he could find & I put an hour meter on it in about 1975 & he sold it to his neighbor in 1995 with 1,300 hours on it, [ I put in 1 power pack for him ] & his neighbor still has that rig & it's got well over 2200 hours on it & runs beautiful.
The 3 cylinder Johnson 70 hp is without a doubt, the very best engine OMC "EVER" made.
My buddy just scored a cylinder on his 1997 - 70 hp because one carb was not working right &* he is buying a new 75hp e-tch & I sent the power head to Blackbird technology in Florida [ also in Penns ] & for $1,700 they are sending me back a completely rebuilt just bolt on engine with 1 year warranty.
They even break the engines in because they say most of the engines that are sent to them weren't broken in correctly & thats why they failed.
The rebuilt engines are 9 bolts, connect the fuel lines from the tank, snap the electrical to the exsisting harness & do it.
I really don't have anything to put the 70 on but for $1,700 I'm not going to turn it down.
Yes, I gave my buddy $500 for it so $2,200 & I've got a sweet engine if needed.
I am looking for a 17' boat just for trolling on the sacramento river as my 20 outrage is way over kill for here so I'll leave it at the coast ,...hopefully we will get a salmon season.
Sorry about the long post.
Back to your engines, treat em good & they will live longer than you.
Sal DiMercurio posted 03-21-2006 11:39 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Forgot to add, my buddy scored a cylinder because 1 carb leaned out because he didn't didn't use his boat for quite a while & the carb clogged up.
Seems the more you run an engine, the better it runs.
The longer it sits with fuel & oil in it, the more problems you have.
BlackMax posted 03-23-2006 02:27 PM ET (US)     Profile for BlackMax    
Thank you all for your ideas. I think I've got a pretty good idea as to what needs to be done to get these running like new. I am going to budget $1500 into the anticipated cost of the rig, which should cover lower unit work, carb teardowns, hoses. gaskets etc. And probably a set of new Mercury Vengeance props, since they come with the old alums.

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