Go Back  The Hull Truth - Boating and Fishing Forum > BOATING FORUMS > The Boating Forum
Reload this Page >

1979 Mercury 70hp takes forever to start! What should i do during off season.

Notices
The Boating Forum

1979 Mercury 70hp takes forever to start! What should i do during off season.

Old 10-24-2020, 02:30 PM
  #1  
Member
Thread Starter
 
Join Date: Jul 2019
Posts: 84
Likes: 0
Received 2 Likes on 2 Posts
Default 1979 Mercury 70hp takes forever to start! What should i do during off season.

I know, its a huge topic and I have read a lot of threads.

I am really hoping someone is familiar with this particular motor.

When it is warm, it starts instantly, just a touch of the key.
When cold, its a good 5-10 minutes. Thank God I have a really good battery.
Every now and then it kind of coughs, not a loud backfire, more like a sneeze.

I hear the relay click when I push in the key. I have tried with priming and without.
i have tried at different trim levels, but generally keep it all the way down.
I have tried not pumping the bulb up to 10 pumps of the bulb.
I figure the first step would be maybe a new hose and bulb? Could it be that simple??
Ha Ha Ha !!!!

I want to give it a good tune up, but apart from plugs, what else is there?
I just want to know if this is a fuel issue or a spark issue. Maybe rebuild the carbs? Change the coils?
Its very weird how well the motor runs after it starts.
Love the sound of this thing!!
Its an old motor and the main reason I bought it was the fact it was one owner, and the compression was 135 across all three cylinders.
Any advice is appreciated, but I am hoping someone has the same motor and has had the same problem.
Cheers!!
Old 10-24-2020, 02:37 PM
  #2  
Admirals Club Admiral's Club Member
 
Join Date: Sep 2019
Location: NE FL
Posts: 606
Received 411 Likes on 210 Posts
Default

I saw the title and the first thought in response was maybe save some money for a new motor? If you want to keep it and need a project I'd say all of the above but with some attention on the choke circuit on the carbs. Not familiar with these motors but 70's tech was a manual choke unless these have an electric choke. The passages in the carb for the could be gummed up too.
Old 10-24-2020, 03:10 PM
  #3  
Member
Thread Starter
 
Join Date: Jul 2019
Posts: 84
Likes: 0
Received 2 Likes on 2 Posts
Default

Thanks, its not even a choke. Its an electric priming system. I can't afford a new motor. the compression is excellent and it runs amazing. I'm hoping someone is familiar with this motor and might be familiar with the cold start issue. But I do appreciate the reply! Cheers
Also, I am in Canada and would buy my parts on Amazon Canada. The problem is its very vague when trying to buy for a specific motor. it would be great if i could get a link to the proper carb kits and maybe even coils.
Old 10-24-2020, 03:41 PM
  #4  
Senior Member
 
Join Date: Jan 2019
Location: San Diego, CA
Posts: 161
Received 315 Likes on 120 Posts
Default

You must become adept at the cold start lever and choke button dance.
Old 10-24-2020, 03:46 PM
  #5  
Senior Member
 
Join Date: Jul 2013
Posts: 4,395
Received 369 Likes on 220 Posts
Default

Most of the time motors that ate hard starting have air leaks, bad fuel lines or connectors or dirty carburetors.
Old 10-25-2020, 08:24 AM
  #6  
Senior MemberCaptains Club Member
 
Join Date: Mar 2003
Location: Annapolis MD USA
Posts: 1,020
Received 231 Likes on 158 Posts
Default

Go through the carbs, fuel lines and priming circut. Simple motor but is cold blooded when perfect. You have to master the cold start technique.
The primer squirts a little fuel each time you push in the key. Sometimes it takes a few pushes.
What is telling though is 5-10 minutes when cold... you really need to clean the carbs.
B
Old 10-25-2020, 09:47 AM
  #7  
Senior MemberCaptains Club Member
 
Join Date: May 2005
Location: Seattle, WA
Posts: 10,517
Received 1,397 Likes on 865 Posts
Default

A 1979 Mercury 70 does not have a primer, it has an electric choke with a manual override.

Use the manual override the next time you try a cold start and see if that makes a difference. That would indicate a problem with the choke solenoid.

This motor should be very easy to start. If it requires a lot of cranking, that suggests the choke is not working properly.

A couple weeks ago I was helping a friend with an old boat he had just bought. It has a 1979 Mercury 80, the four cylinder big brother of this motor. The boat had been in the back of a shed for the last 20 years. We did nothing to the motor except clean the exterior, and plug in a tank of fresh premix fuel. It started right up. I actually think I flooded it a little at first by choking it too long.
Old 10-25-2020, 12:57 PM
  #8  
Senior MemberCaptains Club Member
 
Join Date: Mar 2003
Location: Annapolis MD USA
Posts: 1,020
Received 231 Likes on 158 Posts
Default

OP says he has the electric priming system May not be a 79..
B

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.