1990 70 hp Johnson that suddenly hesitates now and then

Hello all!
I have a 1990 Johnson (70 hp) that I have owned from new and used quite sparingly and mostly in fresh water (maybe 200 hours on it or so).

It has always served me well but last summer it started "hesitating" now and then, with that I mean I am crusing along at 20/25 knots when the engine just suddenly cuts out and drops dramatically in rpm! It actually does not stop but resumes after a second or so...

I have done all the servicing on the engine myself through the years but I have only replaced the spark plugs and the oil in the gear housing every spring. I have also a water separating filter on the fuel line that also has been replaced every spring.

Anyone here that has an idea what could be causing this, I guess it could be quite hard to trouble shoot as it happens only once every hour or so...

Thanks from up by the Arctic Circle!
/Rikard

Re: 1990 70 hp Johnson that suddenly hesitates now and then

Could be a couple of things. I would start with cleaning and re-building the carbs. Also, an ignition coil will act up once it gets warm and make the motor drop rpm's like you describe.

Re: 1990 70 hp Johnson that suddenly hesitates now and then

It could also be the fuel filter going into the VRO pump

Re: 1990 70 hp Johnson that suddenly hesitates now and then

Thanks oldcatamount & Johndhii !

Now, is there such a thing a cut away drawing on a motor like this on the Internet (in order to locate fuel filter and ignition coils), or even some sort of maintenance manual online...?

Or should I buy some sort of repair manual? Any recommendations on what to buy in that case?

/Rikard

Re: 1990 70 hp Johnson that suddenly hesitates now and then

I found the exact one you need. The factory repair manual on ebay for 25 bucks. It's a great deal for you.

http://cgi.ebay.com/ebaymotors/1990...at_Parts_Accessories_Gear&hash=item2c58ddde86

Re: 1990 70 hp Johnson that suddenly hesitates now and then

rikard454 said:

Now, is there such a thing a cut away drawing on a motor like this on the Internet (in order to locate fuel filter and ignition coils), or even some sort of maintenance manual online...?

Click to expand...

Look at www.shop2.evinrude.com and select your engine and then the particular subsystem for a diagram, part numbers, and factory list prices.

Agree that you need a factory service manual if you plan on doing your own work.

As for your problem, I had similar issues once and it turned out to be the quick-connect fitting on a fuel tank. But there are a host of issues that could cause a fuel delivery problem, go through and start eliminating possibilities (for example, do you have a spare tank you could use etc.)

Re: 1990 70 hp Johnson that suddenly hesitates now and then

patrick4266 said:

I found the exact one you need. The factory repair manual on ebay for 25 bucks. It's a great deal for you.

http://cgi.ebay.com/ebaymotors/1990...at_Parts_Accessories_Gear&hash=item2c58ddde86

Click to expand...

Wow, thanks! I might buy that right away but I just noticed that it covers 1973 to 1990 - I just got cold feet, what if my motor is from 1991... Can you judge that by looking at it? Here is a picture:



Any ideas if that is from 1991 and up, I doubt it as I have a strong memory that I bought it in 1990...

Cheers!
/Rikard

Re: 1990 70 hp Johnson that suddenly hesitates now and then

metriccrescentwrench said:

Look at www.shop2.evinrude.com and select your engine and then the particular subsystem for a diagram, part numbers, and factory list prices.

Agree that you need a factory service manual if you plan on doing your own work.

As for your problem, I had similar issues once and it turned out to be the quick-connect fitting on a fuel tank. But there are a host of issues that could cause a fuel delivery problem, go through and start eliminating possibilities (for example, do you have a spare tank you could use etc.)

Click to expand...

Thanks a million, I will try to run it on a separate fuel tank to start with - and replace the inline fuel filter inside the motor as that needs replacing anyway.

And I will get a repair manual as soon as I have figured out that it is indeed a 1990 model I have

Cheers!
/Rikard