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Generic Question / 70 hp Evinrude

Sam110

Regular Contributor
This is about the most 'generic' question one can post regarding engine mechanics but I need a quick answer before this boat sells.

I'm considering a boat that has a 70 hp Evinrude (see pic) that the owners claims does not expel water from the engine except through the prop hub. I don't have a model number or year of the engine (late 80's?) but it does have two dime sized holes in the back of the leg where most engines expel engine cooling water. It does appear the engine has previously been worked on and I'm afraid there is a blockage somewhere within the engine preventing the water to exit the leg if the impeller is working at all. . . UNLESS there are some models that only expel the water out the prop hub. ???

I really like the boat and the owner claims the engine runs good, yet he admits he hasn't replaced the impeller in over 3 yrs. I will continue to research to see what I can determine on my own however I know there some of you guys on here that know your stuff and can give me a pretty accurate answer to my question by just a look at the engine. I know there's really not much to go on but any opinion will help.

Thanks
 

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There should be a wee tell tale that shows that waterpump is working.-----------------Water will come out those 2 holes when you are running full throttle down the lake.----------You may / will not see water coming out of those holes on a hose.--------Operation on a hose is different.------If you buy it then install a new impeller and test the warning horn.-----The hood may be newer than the motor.--------Post the model number.
 
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Hey thanks gentlemen. I did suspect the hood didn't belong but was hoping the mechanics was newer rather than older. I'll have to call the owner for the model number. The boat and TL was purported to me to be an 89. I questioned the hood being different but he didn't know much . . or wouldn't say. Claims that's how he bought it. Said its never given him any problems, so I guess it's getting sufficient water flow. That will be a definite area to barter with I guess should I decide to take the 'plunge'.
 
Check engine operating temperature with a digital infrared temp. gun on various parts of cylinder heads, tell tale stream or not, If on trailer and on earmuffs with hose you can measure temp. of exhaust and water exiting hub before you buy her, I would also have compression test run on her before purchase
 
The green paint indicates clearly to me that it is a JOHNSON model and not newer than 1976.-----------77 models were white again,
 
Found the engine model # to be 70ESL-75B a 75 Johnson. Nothing I can find in the exploded view diagram of a 'telltail' but the holes are there (pic) in the outer exhaust housing. I suppose a new impeller might make a difference too. NADA lists avg retail at $1,020 for this engine. Reliability on the water is my concern with a 40+ yr old motor. The owner has agreed to allow me to run a compression check and run it on a hose with ears on my next visit. Provided all is well, would $500 offer be within reason?
 
75 is a far cry from a late 80s The exhaust relief should spray hot water once the thermostat opens up. You can add a telltale if you want it is not that difficult all you need is athe proper drill and tap to add a fitting on the outer exhaust cover then add the pisser to the lower engine cover.
 
That engine IS NOT as late a model as you are being led to believe. Model/Serial plate being removed is cause to be suspicious. There may be a quarter sized core plug (looks like a small freeze out plug) on the powerhead that has the model/serial numbers imprinted. If so, what are the numbers?

The color of the engine is "Gold" (Not Green) = Evinrude

I edited the picture to lighten it up to view the Model/Serial plate on the port transom bracket. The plate is missing! The year of the engine is most likely somewhere between 1973 to 1976.

NOTE: Pictures of the engine's powerhead, all four sides would be helpful in determining its age.

The paint design of the hood will pin point the year... The design is never repeated, each year is different. Unfortunately my books showing the hood paint job only go back to 1977. (Gold color switched to Blue/Silver in 1979)

Are there two control cables (Throttle/Shift) leading to the engine or one (Throttle)?

If only one = 1968 to 1972 = Hydro Electric Shift = Battery Capacitance Discharge ignition, battery voltage supplied.

If two = 1973 to 1978 = Later model Mechanical Shift = Magneto Capacitance Discharge ignition, voltage self supplied.
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(Exhaust Relief Ports - Exhaust Housing (Inner/Outer)
(J Reeves)

The long housing between the powerhead and the lower unit is called the exhaust housing. There is a inner housing within it that has a heavy duty seal around the bottom of it, or heavy duty seals around a inner extension between the housing and the lower unit.


The red hot exhaust travels down thru that inner tube and out the propeller with a somewhat supply of water to cool the propeller hub. A good amount of water surrounds and fills the space between the outer and inner tube, otherwise the outer housing would get so hot that the paint would burn off.


Some water pumps, for some reason (differing even when new) exert a great amount of water pressure, and if the exhaust housing seals are in perfect condition, the water fills the tube to a point of overflowing.

This brings into play those two holes or slots, whichever the engine might have, at the top rear portion of the exhaust housing just below the powerhead.

Now, if those two holes/slots weren't there, water would continue to flow up into the cylinders. Water not flowing out of those holes is no concern for alarm UNLESS that outer housing suddenly becomes extremely hot..... the warning horn should sound long before that happens.


The main reason for those holes being there (exhaust relief holes) is that when at an idle, there is an extreme amount of resistance encountered by the exhaust trying to escape due the fact that the outlet via the propeller is now blocked by a wall of water. The escape route in this case is for the exhaust to escape out those two holes, otherwise the engine would slow down quite quickly and die. If exhaust cannot escape, air/fuel cannot gain entrance to the engine.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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Thanks Joe for all that input but as racerone points out the model is "70ESL75B" was already given from the ID plate found by the owner as mentioned above. Now the problem I have with this number is that it doesn't eliminate which make, Johnson or an Evinrude ??! I know that basicly they are different only in name and since it was "green" and thereby a Johnson with an Evinrude hood. The serial # starts out with a "J" so I'm going with Johnson. Agree?

Johnnygjr - It was the motor only for $500. I was thinking to be a 'reasonable' offer? It is a boat/motor/TL deal but my bartering power lies mainly in this motor I believe.
 
I saw that model number previously... BUT... the color of the engine, as I edited the picture, came through as I lightened it to look exactly like the "gold" paint that Evinrude used during the early 1970's that I had to lean in that direction, especially since the model/serial plate was missing.

I become very suspicious when that ID plate is removed.

However, in going back to that picture and looking closer, yeah it could be green....but I'd really like to see clear pictures of the powerhead.

However, and I think that racerone will agree with me.... that type lower motor mount was last used in 1977. (2 retainers showing), in 1978, they went to four (4) retainers/bolts.

Actually, it doesn't matter if it's a Evinrude or a Johnson. The only difference between the two in those years was the color of the paint. I wish you luck with your purchase.

70ESL75B = 1975 70hp Johnson, Long Shaft

 
Looking closer myself Joe, the lower cowling does have a goldish hue to it but the leg and below are green. I love the boat itself, a 89 Sylvan SS 16' in really nice shape but I really have my reservations with that motor. Upon looking under the engine cover the power head has been painted and apparently without much care as to what it looked like so I suspect it has had some kind of unprofessional work done previously. Current owner has no record of the motors history prior to his ownership all he can tell me is that it 'starts easy and runs good'. . . how many boat buyers have heard that same claim. I'll run a compression check and run it on the hose with muffs but other than that its a 'crap shoot'.
 
For 1975 they may have used "poetic license " and indeed used the term " gold " in describing the paint colour.-----------Post a picture of the powerhead if you end up with it.
 
Reliability on the water is my concern with a 40+ yr old motor. The owner has agreed to allow me to run a compression check and run it on a hose with ears on my next visit. Provided all is well, would $500 offer be within reason?
$500 for boat and motor is probably fine.

Don't trust the hose muffs. Take a tall rubber maid tub or a barrel that you can fit over the lower unit then fill with water. Starting and running an engine with back pressure on the exhaust can be completely different than running on the muffs. If all is good, there should be ZERO issues with starting and idling in the barrel. A poor running engine can seem to be fine on the muffs because the exhaust is free flowing. Finally, running the engine in a tub forces the water pump to do the work. If you use muffs the hose will pressurize the cooling system and will mask issues with the pump, thermostats, etc. Making the water pump do the work tells you the true health of the cooling system.

KJ
 
Makes complete sense Kevinj, and I've heard it said that running in a barrel is best but I never really gave it any thought as to why. I've got a 3/4 plastic bbl I'll take along. The $500 is my best guess for the motor itself, not the entire rig. He's asking $3,800 for the shebang! I'm thinking 3,000 for it all is reasonable.
 
Check the deck and the transom for dryrot you dont want to buy a slug. Grab the gearbox wit the engine tilted up and if the transom flexes your just buying the engine anyways. If you do not know how to survey a boat take someone with you that does!
 
Sam,

I too am in VA. I sold almost EXACT same boat for about the same price, in MUCH better shape. In fact it is the boat that I rebuilt from the ground up. It is a 16' 1986 Starcraft with all new floors, seats and carpet. The motor is a 1984 75hp evinrude in excellent shape. I did all the basic maintenance on it when I sold it to the guy last year and she was an amazing motor for me.

Anyways, for reference I think you could find a much better boat in better shape with a newer engine for that price. His asking price of $3800 is quite high in my neck of the woods (richmond.)
 
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Thanks rotus, . . . btw I'm in the 'other' VA - "West 'BY GOD' Virginia! haha! but I understand what your saying. Thanks

Sam
 
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