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PostPosted: 09 Apr 2018, 13:09 
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Joined: 26 Mar 2018, 10:08
Posts: 138
Location: Alabama
"seafoam motor treatment" red/white can


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PostPosted: 09 Apr 2018, 14:21 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
Put it in through the spark plugs holes? If so, how much in each cylinder?


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PostPosted: 10 Apr 2018, 16:21 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
Got the seafoam today. Instructions on the can said to put it in through the spark plugs holes and to saturate everything so I put about 2 oz in each cylinder. I'm leaving it to soak overnight.


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PostPosted: 10 Apr 2018, 16:51 
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Joined: 15 May 2010, 00:38
Posts: 2621
Location: Central Florida
Sea Foam is fairly weak compared to one specifically made by Johnson/Evinrude (Engine Tuner) or Mercury or even Yamaha. Hopefully you will see some results with this. If not and you trust your compression gauge it would be well worth pulling the cylinder head, inspect the gasket, pistons, and walls.
If you still suspect that your compression gauge is faulty then replace it and run your numbers with a replacement gauge or borrow a known good one.


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PostPosted: 10 Apr 2018, 19:26 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
Thanks for the info, Pappy. Pulling the head is next if chemicals don't do the job.

I hooked my compression gauge up to my air compressor and compared gauge readings to compressor cut-off pressures. Assuming the compressor gauges are accurate, the compression tester reads about 10 psi low. However, adding 10 psi to the motor reading still isn't good.


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PostPosted: 11 Apr 2018, 18:09 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
I think we made some progress with the seafoam soak. After blowing as much of the seafoam out as possible, I reinstalled the plugs and...

1. Motor actually started with the throttle in the start position, and on the third pull yet. Only ran for a few seconds. Never done that before.

2. Motor would start on full throttle and continue running, but with a bit of a stumble.

3. After running at high speed until the motor was warmed up, I was able to throttle back to medium speed and continue running. However, the smoke coming from that thing was unbelievable. I had to shut the motor down because I couldn't see anything. Hope that was due to burning off the seafoam. If it's going to smoke that bad all the time, I'll have tree-huggers storming my house.

4. You should see the crap that washed out into a fresh fill of the test drum.m


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PostPosted: 11 Apr 2018, 19:08 
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Joined: 15 May 2010, 00:38
Posts: 2621
Location: Central Florida
Yes, that was from the treatment.
Now you need to pull fresh compression numbers.


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PostPosted: 11 Apr 2018, 19:51 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
Did that before installing the plugs. Only a slight improvement. Both cylinders up about 5 psi.


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PostPosted: 11 Apr 2018, 21:41 

Joined: 12 Mar 2017, 12:09
Posts: 555
I would borrow a compression tester from a small engine guy before I tore that motor down. Small displacement piston port engine will use half its oomph overcoming the spring on an automotive gauge. I have a chainsaw that reads 120 on an automotive gauge and 155 on the gauge at the saw shop.
And yeah, those old engines don’t make you feel very good about your environmental footprint! They smoke pretty bad until warm and the garbage can looks like the Exxon Valdez drive through it!


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PostPosted: 13 Apr 2018, 19:24 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
Checked compression again with a second gauge known to be accurate. Unfortunately, it simply confirmed the readings of the first gauge, do there is definitely a compression issue. Not surprising, I guess, for a 62 year old motor.

At any rate, I'm not going to mess with it any longer. I ordered the gasket sets, rings, valve leafs, leaf stops and a new impeller today for a power head rebuild. Will evaluate pistons, rods and associated bushing/bearings once I get the pistons out. I have not located a source for new connecting rod needle bearings so I'm a bit concerned about that.


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PostPosted: 13 Apr 2018, 21:14 
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Joined: 02 Dec 2013, 21:05
Posts: 774
I drug home another 15 Evinrude yesterday and it came with a free 1970ish 9.5 johnson. The 9.5 was in good shape and it had good spark. No start so I cleaned the carb. No start and no compression. I soaked the cylinders overnight in sea foam and still no start. Pulled the head and the gasket was good so I kept spraying the pistons and thumped them with a soft leather mallet to free the rings. The sea foam is weak but after a day of soaking and thumping it fires on the first pull. I would have thought the carbon on the piston would whipe right off with all the soaking but not even close.



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1991 18' Valco Bayrunner Evenrude 48 SPL

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PostPosted: 14 Apr 2018, 09:33 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
The chemicals did seem to help as the motor actually starts and runs, but nowhere near where I would want to be out on the river with it.


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PostPosted: 14 Apr 2018, 17:27 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
Sometimes these manuals just confuses the issue. The parts catalog breakdown diagrams shows the connecting rod needle bearings being uncaged, but the diagrams in the maintenance manual show the caged in 2 sets. Anyone know which is correct?


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PostPosted: 14 Apr 2018, 17:34 
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Joined: 15 May 2010, 00:38
Posts: 2621
Location: Central Florida
As I said before....Seafoam is pretty weak.
At this point why not pull the cylinder head first and see what there is to see and report back.
Pretty sure you will be able to re-use the needles unless the engine was submerged.


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PostPosted: 14 Apr 2018, 18:24 

Joined: 24 Feb 2018, 18:32
Posts: 152
Location: Huntsville, Al.
I've pulled the head, Pappy, and I'm not really seeing anything one would expect to see in a motor this old. There were no apparent problems with the head gasket. There was no measurable warpage in the head and the head was magnifluxed for cracks. There is the usual ring of carbon around the top of each cylinder above TDC, and a accumulation on the pistons tops. Visible portions of the cylinders have some glazing but no signs of scoring or other physical damage.

My concern about the needle bearings is having them go everywhere if they are not caged when I pull the rod end caps off.


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