1997 Johnson 70 HP with all kinds of issues. I need help...

elandesfeind

Recruit
Joined
Aug 7, 2008
Messages
5
Hello everyone!
I'm new to the forum and new to boat ownership, so please pardon my ignorance...
In February, I bought a 17' Key West with a 1997 70 HP Johnson 2 stroke.
The boat sat for at least a year before I bought it. The motor ran fine when I bought it, but I couldn't get it started the next trip. I took it to a local mechanic and he found a cracked line (he wasn't specific about what line it was) and he replaced it. After that, the boat ran fine. I run the boat at least twice a week and it ran great for almost 5 months, but it's developed a "few" problems since then. The problems have started in the following order...
1) The tachometer has stopped working properly. It reads correctly from idle up to around 2000 RPM, but then quits, with the needle returning to the peg.
2) Last month, I noticed that after running the boat and letting it sit, there is some fuel that leaks out of the seal on the carburetors. It's less than a teaspoon full of fuel that leaks out after the boat sits overnight. If it sits longer than that, no additional fuel leaks out.
3) Last week, the motor started smoking more at idle. I haven't changed my oil mixture and the boat hasn't sat for more than 5 days. Before every trip, I put in 5 gallons of gas and 13 ounces of oil.
4) The trip after the motor started smoking more, I noticed that it ran very rough in the 2000-2500 RPM range (I'm guessing at that because the tach stopped working). It's a little rough at idle, but not unusually so and once I open it up past 1/2 throttle it runs great.

Thanks in advance for taking the time to help out a newbie boat owner!
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 1997 Johnson 70 HP with all kinds of issues. I need help...

First off, welcome to iboats.

I think you may have a couple problems to deal with here.

First off, it is likely that your carbs need to be bathed/rebuilt.

Secondly, your regulator/rectifier may be failing once warm. This would explain the tach malfunction. If you have a multimeter and am able to use it, see the FAQ section on this website for a thread by Joe Reeves for testing it.

Are you pre mixing your fuel or is your OMS still functional?
 

elandesfeind

Recruit
Joined
Aug 7, 2008
Messages
5
Re: 1997 Johnson 70 HP with all kinds of issues. I need help...

Thanks for the response and the welcome!
I'm premixing my gas. As far as the tach goes, it doesn't matter what temp the motor is running. It stops working the moment I go past 2000 RPM hot or cold. Being a new boat owner, I'm not familiar with rebuilding a carb. Is it something that a novice could tackle or do I need to take it to a mechanic?
 

199675hpforce

Petty Officer 1st Class
Joined
Feb 27, 2004
Messages
299
Re: 1997 Johnson 70 HP with all kinds of issues. I need help...

First off its prolly just fuel maybe fuel pump. They make diaphram kits $20 order one now! Id also get a carb rebuild kit but thats me the season will be over fast so hurry. Get a manual those help out and you learn about the motor and tuning. I wouldnt take my outboard to a mecanic rather do it myself and learn. Also once you start working on her you can ask more questions. Go to marine store they should have the parts my problem my diaphram kit is sold out booo so i ordered at a local marine and still waiting.
 

HighTrim

Supreme Mariner
Joined
Jun 21, 2007
Messages
10,486
Re: 1997 Johnson 70 HP with all kinds of issues. I need help...

Go to the FAQ and look for a thread by Tashasdaddy regarding rebuilding the carbs. That, along with this forum, and a factory service manual, will get you through fine. Hardest part if any is just simply removing it, then go through the motions. Have a look at the video in the thread I mentioned in the FAQ as well. I also still believe that you should check your rectifier. Do you have access to a multimeter?

Let us know how you do, good luck!
 
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