'63 75Hp Johnson Slow and Sucking Gas

[samuelcosmoschiff]

Hey all... Yet another problem with the old motor...

Johnson 75 horse V4AL-15E.... Pretty slow at wot, and I only got about 30 minutes of running out of 10 gallons of gas (the trip ended in an $85 tow back to the marina after i got stuck in the middle of the lake).

Before I ran out of gas, however, she started to pick up and I was zipping around for about 5 minutes. Also, she only likes to stay running with the choke in the "on" position; putting it to "automatic" or "off" results in a few minutes of running and eventually quitting.

Waddaya think? I was going to do a tune up to start...

 

[boobie]

Re: '63 75Hp Johnson Slow and Sucking Gas

When you start to do the tune up look closely at your fuel system. Fuel lines, fuel pump and carb.

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Sorry for the long delay, finally got back down to the boat earlier this week.

Replaced the plugs to the correct J8C (instead of J4C that was in there), fuel filter, and lines.

Still running kind of crappy, so I added a bottle of seafoam to a gallon of gas and ran it through. An incredible amount of smoke came out of the engine, and I think it helped some, but still not perfect. At WOT she will go about 10 mph (according to my GPS). However, after ten or so minutes at WOT she picks up and gets up to 20 mph. Still burning lots of gas, too; almost half of a twelve gallon tank in 30 or so minutes.

Any thoughts are much appreciated. At this point I'm thinking I'm going to go for round two with the seafoam...

 

[Chris1956]

Re: '63 75Hp Johnson Slow and Sucking Gas

Sounds like she is only running on 2 cylinders. Check compression on all. Pull the pulse line off the fuel pump and see if any fuel comes out. Also sounds like the carb is clogged. Seafoam may (may) help a little, but likely not enough. See if you can get a carb kit and clean her up.

 

[boobie]

Re: '63 75Hp Johnson Slow and Sucking Gas

J8C ???? Where did you get that info from?? The correct plug is J4C or you might get away with J6C.

 

[boobie]

Re: '63 75Hp Johnson Slow and Sucking Gas

What's the compression on it?? Will the spark jump a 1/4 " open air gap on all 4 cyl's ??

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Yikes! J8C was listed in the champion book. I guess I should have stuck with what was in there before. Did I do any damage by using the wrong one?

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Also, I didn't see if the spark would jump, but I did ohm out all the wires and they read good... 1 ohm on all. They're pretty nasty looking though, so I'm in the process of finding a new set.

 

[boobie]

Re: '63 75Hp Johnson Slow and Sucking Gas

If you didn't run the J8C's for long you should be okay. Read post # 6 again.

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Not sure about the compression, don't have a gauge but will pick one up.

Do you mean will the spark jump when I hold the wire end a quarter inch from the block?

 

[DMontana]

Re: '63 75Hp Johnson Slow and Sucking Gas

Not sure about the compression, don't have a gauge but will pick one up.

Do you mean will the spark jump when I hold the wire end a quarter inch from the block?

You can buy an adjustable spark gap tester at just about any auto parts store, and set it for the desired gap.

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Good spark on all cylinders. No gauge but when I turn the engine by hand it feels like it has even compression (is that valid at all?).

I also rebuilt the fuel pump, because I needed a filter and the kit came with one for $15.... not bad.

On to a carb rebuild I guess...

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Rebuilt the carb. Man it was dirty!

Performance improved substantially. The boat moves nicely now, although it still takes the engine a few minutes to reach top rpm.

Anyone know what the points gap is on this engine?

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

.02 ....nevermind.

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

Finally got a compression gauge...

80 PSI on all four cylinders. Is that good or bad?

 

[Chris1956]

Re: '63 75Hp Johnson Slow and Sucking Gas

That compression is acceptable. The fact that it is even is what is important. I expect your compression gauge reads low by 10PSI, as 90 PSI is pretty normal for those motors.

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

That could be, it was a cheapo gauge from ebay.

So the compression is ok... why am I not getting up to speed until she's run at wot for a while then? What the heck am I missing?!

Just to re-cap:
-New plugs
-New Wires
-Spark is good
-New fuel lines and filter, pump rebuilt
-Carb Rebuilt
-Cleaned and gaped points
-Doesn't reach top rpm until run at WOT for at least a few minutes, sometimes not at all

Again guys, thanks for the help

 

[Chris1956]

Re: '63 75Hp Johnson Slow and Sucking Gas

What do the spark plugs look like? Maybe you are missing on one plug sometimes? What size and type of boat? You cleaned and gapped both sets of points, to .020?

 

[samuelcosmoschiff]

Re: '63 75Hp Johnson Slow and Sucking Gas

The plugs look good.... light brown, not fouled.

Its an 18ft tri hull bow rider. Yep, cleaned and gapped to .02.

 

[pn]

Re: '63 75Hp Johnson Slow and Sucking Gas

have you tried pumping the primer when it luggs. a boost would indicate fuel flow.