Re: 1983 85HP: My compression results- what are the plugs telling me?
OK, already changed the plugs after the compression test. Will clean the old plugs and have them for spares. The plugs were from 2004 according to the receipts from the previous owner. The PO gave me a box of new plugs since he said his boat mechanic only used them for his boat and had to order a one box minimum.
Every time I’ve put gas in the tank, I’ve always done the 50:1 mix, but what about what’s already been in there? There have been periods during the last 5 years that where to boat has been just sitting in a garage (the prior two years with me). How do I take that into account?
Decarbonization afterward: do I do Power Tune or Sea Foam via the gas tank or just spray into carbs while revving in the driveway or both?
Thanx.
As per indication of carbon buildup on your plugs, I would do the seafoam spray directly into the carbs. This is what I do for de-carboning:
1. With plugs remove, spray seafoam directly into each cylinder to soak the carbon buildup; re-install plugs
2. Let is soak for hours I do it overnight by spraying in the late afternoon
3. Next day, rig the water and muffs and get oil pan to cover the pavement for carbon release
4. Fire her up and warm up for about 2~3 minutes. In your case you will need to remove the carb cover to spray directly into it
5. Using the throttle linkage bar or timing tower, rev her up (racing) but no more than 3500 rpm a few seconds at a time while directly spraying sea foam or power tune into the carbs.
6. The engine can bog down if you spray too much so start low spray and increase as required
7. Watch the exhaust and you should see carbon dust exhausting.
8. Continue doing this until no more dust coming out or dust exhaust is very light
9. Stop engine cool her down and inspect plugs. They should look very clean almost like steam cleaned.
If you are hesitant to do the above, you can just do the tank treatment but it will take more than a tankful of gas to clean up all the carbon buildup depending on how often you run at WOT speed. For future operations, avoid running the engine at idle for a long time and only when necessary. Prolong idling is the biggest cause of carbon build up.
In the future, I recommend using NGK's BUHX or BUHW for plugs. They seem to have better performance for their versatile voltage requirement, which is lower than Champion ULV's.
