January 12, 2017 at 11:27 pm #50921quote Chris_P:
No chunks missing,this is a fairly deep groove, but the rest of the scoring is light.January 12, 2017 at 11:28 pm #50922
You can see the rust rings the wristpin circlips lift in the bore, this was a salt water motor with a lot of damage, the head gasket was also leaking. This block is most likely junk. I had to build up with JB weld and file flat the midsection surface that the powerhead bolts to because so much material was missing. I probably picked one of the worst 18hp motors out there.January 13, 2017 at 12:43 am #50927
Just for fun I checked the ring gap on the old motor:
ring 1 = .022
ring 2= larger than .035
ring 3 = larger than .035
ring 1 = .023
ring 2 = .018
ring 3 = .012January 13, 2017 at 1:33 am #50929
Stephen….stop trying to talk yourself into a myth. The pistons , rings and bores are bad. Sugar coat it any way you want but the advise you have received here is from guys that have been there and done that hundreds of times. Frank, Chris and Fleetwin would not steer you wrong. When a motor is worn out… well… It’s worn out.January 13, 2017 at 1:39 am #50931
Thanks wannabe, keep in mind the pics I posted are of my old powerhead. It does sound like my current powerhead could be bad as well, knowing the totally toasted one made 90 PSI, my "good" powerhead that made 100 PSI might be in bad shape as well.January 13, 2017 at 2:03 am #50932
I found the ebay ad for the powerhead I have, the seller said it had 125psi top and bottom.
US Member - 1 Year
Topics: 70January 13, 2017 at 2:58 am #50937
You really have to watch the compression gauge closely, to see how fast they pump up while cranking. I had an 18 a little older than yours that had near 95 psi, but the pistons were scored from overheating. Its a good idea to pull the intake port covers and have a look before purchasing. These old engines would run so good for so long, that folks wouldn’t bother with impeller maintenance! Then one good over heat would spell the end for an otherwise good engine.January 13, 2017 at 3:02 am #50938quote Jerry Ahrens:
When pulling the rope, if the rings/bore are good, should it only take about one pull to build max PSI?January 13, 2017 at 3:15 am #50940
I found this on iboats, plan to try it:
"wot drop to idle and it wants to die points towards a loss in crankcase pressure…try this sequence, wot, quick drop to idle, quick snap to 1/2 throttle….if the engine won’t recover and dies this points towards leaking or loss of crankcase pressure in 2 strokes < this assumes the ignition and fuel delivery are ruled out >…causes?…crank seals, crankcase halves seam leaking, worn piston to cylinder tolerances, loss somewhere else."January 13, 2017 at 12:37 pm #50954
One other thing to think about Stephen. Just because it makes compression when doing the compression test, whats not being measured is "blow by". As was stated earlier in this thread, a leak down test will most likely reveal that it is not holding that cylinder pressure for the complete combustion stroke. That is where the significant power loss comes from. The pressure is leaking past the rings.
Also, be very careful when buying powerheads from Ebay. They show you a compression gauge pegged at say 120lbs. and state the power head "has great compression". Last winter I had a 66 FD 20 with 120 on top cylinder, 60 on the bottom. If i put about a teaspoon of 2 stroke oil in that bottom cylinder I could get it to read 95psi. on the gauge. You see where I’m going with this? Buyer beware.January 13, 2017 at 12:51 pm #50955quote wannabe outboard guy:
Point taken, I think I’ll buy a leakdown guage and do the test.January 13, 2017 at 12:53 pm #50956
re read my last post, as I have edited it.
US Member - 1 Year
Topics: 52January 13, 2017 at 9:22 pm #50979
I had a cheapie compression gauge a few years back that had the check valve at the far end of the rubber hose (the cylinder end), so unless you were measuring a big cylinder, like in a big car engine, the volume of space in the hose between the checkvalve and the gauge offset the readings down significantly. Be sure you don’t have that problem. I tossed that one out.
Topics: 0January 13, 2017 at 11:43 pm #50988quote outbdnut2:
My "Snap-on" gauge is like that,,,,I don’t think I am going to toss it!
US Member - 2 Years
Topics: 37January 14, 2017 at 12:47 am #50993
My compression gauge has a hose about 12" long. I don’t find it errors to the low side if you continue to crank until the needle stops. For a rope start outboard I find it usually takes about 4 brisk pulls of the rope. I usually give 5 just for good measure.
OldJohnnyRude on YouTube
You must be logged in to reply to this topic.