1973 115HP rude fuel issue?

jaurora

Seaman
Joined
Jun 29, 2007
Messages
66
Hello all,

You have been a big help to me so far and I was hoping that someone may have come across this issue that I am seeing. Bought this motor and been working on it a little at a time and I think I have the issue narroed down to a fuel problem.
On this motor the comprssion on all 4 is good, spark is good, carbs have been rebuilt.
The problem that I have is the motor dosent seem to be getting fuel, after cranking it several times and nothing, I pulled the plugs and they are all bone dry, no matter how much you turn the engine the plugs stay dry, so I pulled the front off and checked the reeds, all which are functioning correctly and no corrosin or damage to them, replaced the head and turned the motor and there is great suction from the reeds. I put the carbs back on, turned the motor and I am not seeing any fuel what so ever inside the carbs, the bowls of the carbs are full on both and the primer ball is rock hard. I think this was an existing issue from the previous owner as there is a new fuel pump installed. I pulled the feed from the fuel pum and turned the engine, there were spurts of gas as I would imagine seeing, not quite sure how much pressure it should be but if I put my finger over the line ant turn the engine it was NOT enough pressure to push gas past my finger. Now I can see that these fuel pumps operate on vaccume, so I disconnected the vacume line and there were pulses of suction, not stong but enough to feel.

So that is where I am right now with this motor and was hoping that someone has been there done that type of deal. So a quick list of things that have been checked.

Compression 120 on 3 and 105 on 1
Spark, nice spark on all 4 which jump the 7/16 gap.
Reeds, all function and good condition.
Carbs, all clean and bowls filled with gas. (When i look into the carbs during engine crank i see no gas at all)
Fuel pump, new from previous owner, thats all I know about that.

Thank you for anyone having any idea as to what this issue can be, im stummped!

jeremy
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: 1973 115HP rude fuel issue?

The fact that you have gasoline in the carburetor float chambers makes the fuel pump issue moot for the moment. That is, the fuel pump could be non existent..... the engine should still start and run on what is in the carburetors.

The 15 psi difference between the highest and lowest compression reading is not a good sign BUT the engine should still start.

Proper starting procedure is: Pump fuel primer bulb until it is hard, apply some throttle to crack the throttle butterflies open somewhat without putting engine in gear, turn key to the START position and push in key (or engage choke switch) to close choke butterflies at the same time. When engine starts, release key to drop back to the ON position.

If this is your starting procedure, remove the carburetor face plate and check visually to see if the choke butterflies are closing or not.

Let us know what you find.
 

crb478

Lieutenant Junior Grade
Joined
Dec 6, 2006
Messages
1,036
Re: 1973 115HP rude fuel issue?

To go along with what Joe Reeves said, how are your cables,battery, and starter? The engine needs to spin at around 300 rpm's to start. If it is not spinning fast enough it will not suck fuel into the cylinders. You could try to spray a little pre mix directly into the carbs to see if you can get it to fire.
 

jaurora

Seaman
Joined
Jun 29, 2007
Messages
66
Re: 1973 115HP rude fuel issue?

Thank you for your replys.

The battery is good and the engine is spinning fine. As for the startup procedure that has all been done as well. I actually tried starting up the motor and spraying some starting fluid in but still nothing which was what led me to be the reeds were sticking as I did not even smell that near the plugs, If I pull all the plugs out and try turning it over no fuel comes out of the cylinders either. I am truly stumpped. I noticed if it crank the motor and blow into the carps I can then see the gas spray out.
 

jaurora

Seaman
Joined
Jun 29, 2007
Messages
66
Re: 1973 115HP rude fuel issue?

just noticed i spelled carps instead of carbs. sorry
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 1973 115HP rude fuel issue?

thats better than having crabs.
 

mikesea

Lieutenant Commander
Joined
Oct 1, 2006
Messages
1,830
Re: 1973 115HP rude fuel issue?

You need to insure your choke is operating,just because you hear it or see the linkage MOVE dont mean the butterflies are closing.If possible ,have someone crank the eng.while you manually close the CHOKE butterflies.It might be easier for you to remove the plastic carb cover,you will then be able to see the choke better.You can also get a spray bottle and put some fuel oil mix in it,spray into each carb by opening up the throttle spray into each barrell of the carbs,then crank it,if you by yourself.DONT use starting fluid.It has no lubrication,AND it evaporates fast,make sure the throttle plates are open to allow the fuel to get into the reed cage,or it hits plates rolling out the carb
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: 1973 115HP rude fuel issue?

Did you remove the carburetor face plate to visually check to see if those choke butterflies were closing as I suggested? Also, if that choke colenoid is a two wire solenoid, apply the following.

(Temperature Actuated Choke Solenoid Conversion)
(J. Reeves)

Various OMC engines that were manufactured in the later 1960s thru the early 1970s, for example the 1969 55hp Evinrude/Johnson incorporated a dual stage choke solenoid...... easy to identify as they have two wires leading to the solenoid, one purple/white, one purple/yellow.

The purple/yellow is attached at the engine wiring terminal strip to another purple/yellow wire that led to a heat sensor. The initial stage, with the key ON, (purple/yellow), when cold, would keep the choke pulled in half way until the engine warmed up, at which time it would release and open the choke butterfly.

The second stage (purple/white) is attached to another purple/white wire at the engine terminal strip which leads to the choke switch. When the switch was engaged, the choke closed etc.

The problem with this setup is that as the engine got older, the thermostat acted up, water pump became weak, whatever, the heat sensor failed to operate properly and the choke would not release from that half closed position. This would cause the engine to run in a rich fuel mixture condition (flooding, loading up).

The cure to this problem, via a service bulletin from OMC was to remove the solenoid purple/yellow wire from its original location and connect both of the solenoid wires (purple/yellow & purple/white) to the engine wiring harness purple/white wire at the engine terminal strip.

The above change would allow both solenoid wires to be energized when the choke switch is engaged, pulling the choke butterfly in firmly..... and only when the choke switch is engaged.
 

jaurora

Seaman
Joined
Jun 29, 2007
Messages
66
Re: 1973 115HP rude fuel issue?

Hello All,

Here is an update, come to find out that one of the butterflys for the choke was not closing 100% like the other one. Simple adjustment on the linkage did the trick along with a freshly juiced battery. Now more problems exist, fuel is no longer the issue, it now turns into an erratic spark issue, some times there is a little spark, some times there is great spark and sometimes there is no spark. After going through the manual there was a test to remove the sensor wires from the power pack and measure the resistance, the book said both should be ~8.5ohms +/-2, the first reading was perfect and the second one kicked the needle to 0 ohms which indicates a short. Needless to say it looks like after the testing that i will have to replace the timer base, that seems to be like the most expensive part on the motor.

Thank you for all of your help.
Jeremy
 
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