new boat owner! any info will help! 1977 johnson 70hp outboard motor

ni_cole_b

Cadet
Joined
Mar 12, 2015
Messages
7
I recently bought a 1977 Orion fishing boat and it has a johnson hp70 outboard motor. I'm new to the boating life so I was hoping I could get a lil info, advise, knowledge from you about my motor. As far as gas/oil mixuter, type of gasoline that's recommended, information about cleaning the carborater & plugs. When I 1st bought it, it had a half tank of gas (3gals) I took it on the water & it ran great, had speed & power. Didn't have no problems, but then I went to take it out for a second time and had to refuel the tank. It had a lil gas left in it but not too much, so I did as previous owner said put 1pint of 2cycle marine oil to 6galons of gas. I used the basic 87 unleaded gas you get at a gas station. When I hit the water my boat had a hard time starting, when I finally got it started it had no power or speed. And sometimes even shut off on me. It would turn right back on immediately but I just putt putted around the lake. A very different experience for me compared to my 1st run. Do you have any helpful tips for me? Id really appreciate it! -Nicole
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Check to be sure you have spark to all 3 cyls when you think it's not performing well. A cyl drop test is a good one, or you can check for spark with an automotive timing light. Make sure the engine is well warmed up when doing a spark test.
 

eavega

Lieutenant
Joined
Apr 29, 2008
Messages
1,377
You might also want to inspect the carburetors. If you had a good run, then all of a sudden you are not working right, some bit of crud might have broken loose and is now plugging a jet somewhere.

Another good indicator that you are not running all three cylinders is if you run it on a hose and an excessive amount of sludge is coming out the exhaust. That sludge is unburnt fuel/oil mix and would indicate you are not getting combustion in one or more of the cylinders.

In any case, as the previous folks have suggested, do a cylinder drop test to make sure all three cylinders are sparking. If you find you are getting spark on all three cylinders, then you need to absolutely verify you are getting fuel to all cylinders, as running one lean will destroy the engine.

Good luck

-E
 

ni_cole_b

Cadet
Joined
Mar 12, 2015
Messages
7
Thank u all for the tips & suggestion! I can't wait till Sunday to get out & test them all out! Ill update as soon as I find out more! Greatly appreciative -Nicole
 

ssportsmfg

Seaman Apprentice
Joined
Oct 7, 2014
Messages
42
I had that engine in 1988 version, had a lot of problems with it, mostly the inside of the hoses clogging the carbs up with pieces of rubber. Great engine when running right. The carbs are very simple, and you can get rebuild kits for them, if you take them off and find black rubber particles in them, put all new fuel lines on, and then clean out or rebuild the carbs. I had mine on a 18ft wide river john. It would fly at about 55 mph. I put a 20 gal tank in mine as I run the Mississippi river and 6 gal is not enough to get anywhere.

A rule of thumb is take the hp of the outboard and it will burn that much fuel in one hour...ie. 70 hp = 7 gals per hour. So you will have less than an hour run time at WOT.

HTH's
 

ni_cole_b

Cadet
Joined
Mar 12, 2015
Messages
7
Hey guys, so I did all that was suggested and im going to take it for a test run soon. But I have another question. On the left hand side of the engine where the fuel filter is, on that metal part there is a tiny hole that leaks gas. The hole looks like it was manufactured like that so im not sure if it was made to leak gas or is that an issue? Any advice will help! Thanks again!
 

ni_cole_b

Cadet
Joined
Mar 12, 2015
Messages
7
Here is a picture of what im talking about & the yellow arrow is where it leaks from. QuickMemo+_2015-04-19-15-57-28-1.png
 

henleyhale

Petty Officer 2nd Class
Joined
Oct 5, 2013
Messages
136
that is a vaccum pump. i.e. your fuel pump and if your leaking gas out of it you need to remove it and rebuild it. sounds like your vaccum has made a hole in the rubbers and is sucking up huge gulps of air. to test the theory. start the motor and spray starting fluid at that hole in short bursts. if the engine revs up with that then you have found your issue.
 
Top