Newly bought Johnson 7.5

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Gage R

Cadet
Joined
Feb 23, 2021
Messages
7
Hey everyone. I have no experience with outboard motors so disclaimer for anyone who doesn't have patience, lol

Anyways,
I just bought a johnson 7.5 seahorse as part of a boat/trailer buy and it is not running.
It looks to be around the 1980 model but I am not sure.

What I know so far is the gasoline can pass through the filter and towards the carburetor & both spark plugs are working good. When pulling the start rope, the sparks do not get any fuel on them. I've tried taking the carb off but the second bolt is hidden behind a few of the starter mechanisms.

What do I try first?
 
tpenfield

tpenfield

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Staff member
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Jul 18, 2011
Messages
18,449
Welcome to iBoats . . . :D

I have a 4.5 HP Johnson motor of similar vintage. If you can get gasoline to flow to the carburetor, see if you can get gasoline to drip out of the carburetor. That would be a sign that the main jet is not fully clogged (which it may be).

Tell us how you verified that you were getting spark at the plugs.

It would be best if you can get the carburetor off for disassembly and cleaning . . . maybe even a rebuild. See if you can get at the fasteners by removing things that are in the way.

The fuel mix should be 50:1 gas/oil, so make sure that is right.
 
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Crosbyman

Vice Admiral
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Nov 5, 2006
Messages
5,810
don't forget to change the impeller (age unknown to you) and replace the gearcase oil (see if any water got in if so a GC reseal may be in order. use new nylon washers as it may be just the washers not doing their job to seal the GC)

unscrrew the top Idle adjustment . needle a half turn see if that helps
readjust it later

spay some fuel in the carb face see if that wakes it up.
 
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iggyw1

Ensign
Joined
Oct 24, 2011
Messages
954
When you try starting it when it's in your yard or driveway, make sure you have water in a big drum or garbage can and about 8" higher than where the water ompellor is in the motor. Do not run it dry. You can give it a shot of ether into the carb to see if she will try to start, but I would first remove the plugs and shoot a little it of fogging oil into the pistons so she does not start with the ether and not lube in the fuel. (Some ether has oil in it for strting a two stroke engine. Read the label). Start with fresh gas too. If it does start up for you, run a good dose of Sea Foam in the fuel tank to clean things up.
 
G

Gage R

Cadet
Joined
Feb 23, 2021
Messages
7
tpenfield said:
Welcome to iBoats . . . :D

I have a 4.5 HP Johnson motor of similar vintage. If you can get gasoline to flow to the carburetor, see if you can get gasoline to drip out of the carburetor. That would be a sign that the main jet is not fully clogged (which it may be).

Tell us how you verified that you were getting spark at the plugs.

It would be best if you can get the carburetor off for disassembly and cleaning . . . maybe even a rebuild. See if you can get at the fasteners by removing things that are in the way.

The fuel mix should be 50:1 gas/oil, so make sure that is right.
Click to expand...
Thank you! Yeah, I definitely need to start with a carb clean. I unscrewed both sparks and then had a friend pull the starter rope as I grounded the plugged-in plugs. Both had a little spark. The previous dude had 2.5+ year old gas in it, so I did a fuel rinse and I'm using fresh 50:1. I tried looking up a video of taking off the stuff in the way and he skipped it and said "After 11 steps I got it off". Sucks haha. Thanks for replying!
 
G

Gage R

Cadet
Joined
Feb 23, 2021
Messages
7
Crosbyman said:
don't forget to change the impeller (age unknown to you) and replace the gearcase oil (see if any water got in if so a GC reseal may be in order. use new nylon washers as it may be just the washers not doing their job to seal the GC)

unscrrew the top Idle adjustment . needle a half turn see if that helps
readjust it later

spay some fuel in the carb face see if that wakes it up.
Click to expand...
Would it just be the little gear part of the impeller or the whole system?
 
G

Gage R

Cadet
Joined
Feb 23, 2021
Messages
7
iggyw1 said:
When you try starting it when it's in your yard or driveway, make sure you have water in a big drum or garbage can and about 8" higher than where the water ompellor is in the motor. Do not run it dry. You can give it a shot of ether into the carb to see if she will try to start, but I would first remove the plugs and shoot a little it of fogging oil into the pistons so she does not start with the ether and not lube in the fuel. (Some ether has oil in it for strting a two stroke engine. Read the label). Start with fresh gas too. If it does start up for you, run a good dose of Sea Foam in the fuel tank to clean things up.
Click to expand...
Whoops, I had the prop in a bucket of water but didn't know it needed to be that high up, I can only hope that's one of the main issues, lol.
 
R

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,880
Fact----You remove the 2 small screws at the top of the recoil starter.----Have your assistant lean the starter out of the way .----Then remove the 2 nuts to get the carburetor off.
 
G

Gage R

Cadet
Joined
Feb 23, 2021
Messages
7
racerone said:
Fact----You remove the 2 small screws at the top of the recoil starter.----Have your assistant lean the starter out of the way .----Then remove the 2 nuts to get the carburetor off.
Click to expand...
I went out to look for the 2 screws on top and I could not find them. Just looks like a bunch of nuts and bolts. Thanks for responding
 
R

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,880
??----Are there not 2 screws 1/4-20NC thread at the top ??-----Model # of your motor ?
 
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cprodave

Petty Officer 1st Class
Joined
Jul 1, 2012
Messages
301
Gage R, those old 7.5hp are good motors. Go to "Leeroy's Ramblings" if you want to learn how to disassemble debug and maintain those old gems.
 
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