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70 HP Evinrude, Idle Vibrations

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petkovski

Member
I have a 1990 Evinrude 70 HP VRO. I don't know much about the service history, what I do know is that it belonged to an old man who drived it a few times a year.

When I got it, I've changed the lower unit oil, put new sparkplugs, confirmed that the vro is sucking oil and that's it.

I manage to start the engine after a couple of times trying on a cold start, but after that is working fine.

When idle, neutral or gear it's vibrating. If you put a glass of water on top of it, it would probably spill the water, but the glass would stay. When I add throtle, and above 2000 rpm, everything is fine, I had it driving over 5000, works perfectly.

My dad thought, maybe it's running or 2 cylinders, and I was like, it's nothing it's supposed to be like that. After I got back home, I googled and saw a few videos and the other engines from this range weren't vibrating like that.

Is this normal? What do you think it is?
I don't have good experience with marine engines, except the basics, change oil, put new sparkplugs, carb, etc.

Thanks
 
Start with the basics............

Check the compression of each cylinders. What are the psi readings?

Check the spark with all spark plugs removed... it should jump a 7/16" gap on all cylinders with a strong blue lightning like flame, a real SNAP! Does it? Note that the 7/16" gap is important... checking spark by using the spark plugs is a waste of time.

If the above is as it should be... the most common problem is that the carburetors are fouled and require cleaning and rebuilding.

Let us know what you find.
 
How to check the compression? Is there a tool or something? We don't have a service / repair shop for this kind of things were I live, so I'm only at the mercy of the net. What is a 7/16" gap?
 
A compression gauge can be loaned or purchased from most automotive part stores. Have all spark plugs removed, press the rubber tip of the gauge into the spark plug hole and have someone crank the engine over. Keep the plug wires away from the gauge! (shocking)

A 7/16" gap is a air gap for the spark to jump. Gauges can be purchased (auto stores) of built as follows.

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.


Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:




..........X1..........X2


.................X..(grd)


..........X3..........X4

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
 
Really thanks for the advice. I will inspect the engine more closely at the weekend, and I'll send you some photos so you can see the overall condition of the engine. If I need parts or something, I will definitely look out for you!
 
One of my statements in my previous reply came out as "A 7/16" gap is a air gap for the spark to jump. Gauges can be purchased (auto stores) of built as follows."

It should have read as "A 7/16" gap is a air gap for the spark to jump. Gauges can be purchased (auto stores) or built as follows."
 
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