Power loss on my 1977 Johnson 140hp, Please help?!!

[texasatm2011]

Howdy everyone,

I have a 1977 Johnson 140hp outboard. I can't figure out what the problem is. It starts up fine and idles OK, I then start to throttle up and I have as much power as I want.
Your probably thinking 'Wheres the problem?!' Well, here it is, as I'm going, I randomly lose power. The engine is still running but no matter how much throttle I give it I can't seem to go any faster than 5 or 6 miles an hour. Then after a few minutes, all the power seems to come back.

It ran great for most of last summer but I started to have this problem late in the summer. Can anyone please help me out?!!!!

 

[emdsapmgr]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

Your ignition system may be dropping a cylinder. When you have running issues, put an inductive timing light on each of the 4 plugwires. Check for strong spark. The light flashes will show nofires, weak fires and intermittents.

 

[texasatm2011]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

Where do I get something like that?
What causes a problem like that?

Thanks for the help!

 

[emdsapmgr]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

Most auto parts stores rent various tools. That ignition system consists of a stator, timer base, power pack and 4 coils. Any of them could be the problem. Typically, weak ignition components act up once the engine gets warmed up to normal operating temps.

 

[texasatm2011]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

I had the coils and the power pack looked at earlier this year and everything looked good. So it could possibly be one of the other two.

I've called around to a few places and so far I haven't been able to track one of those tools down but I'll find one eventually!

I also noticed that the gas tank seems to be really dirty, almost rusty looking, do you think something from the tank could be contributing to the problem?

Thanks again for the help!

 

[emdsapmgr]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

It's easy to check for bad spark. Good place to start your troubleshooting. Once you find the spark is good, then you can go on to fuel delivery as the issue.

 

[tashasdaddy]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

i run the same motor, how old is the gas? when it starts to slow down. immediately stop and check spark on all 4 cylinders.

 

[ezeke]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

Where do I get something like that?
What causes a problem like that?

Thanks for the help!

Get one of these, if you put CP7529 in your search engine you should find one for around $70. The tach is a good extra value: http://www.amazon.com/Actron-CP7529-Digital-Timing-Light/product-reviews/B000BSY9JE

 

[Pokertrampp]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

The engine is still running but no matter how much throttle I give it I can't seem to go any faster than 5 or 6 miles an hour. Then after a few minutes, all the power seems to come back.

You say your losing power and can only go 5 or 6 mph, are you losing rpm's or just speed, it sounds like just speed they way you have it worded. if that is the case, have you checked for a spun prop?

 

[texasatm2011]

Re: Power loss on my 1977 Johnson 140hp, Please help?!!

I'm just losing speed, not RPMs. When I begin to slow down the engine still seems to be working pretty hard and I have to have the throttle cranked up relatively high ( somewhere around 1/2 throttle) to even go 5 or six mph.

I thought it might be a spun prop but I put another one on there and it did the same thing. (This was another old prop so I'm not sure how accurate the test is)

ezeke,Thanks for the link, I think I'll take a look at it