Since we have had this boat we have used it about 5 times with a total of maybe 6 hours running. TBH, much of the time it ran really sweet, however, yesterday we had an issue. We were coming in from about 5 miles out, when in the estuary approaches the engine suddenly sounded rough, slowed, would not respond to the throttle, and then stalled. A quick flick of the starter indicated my worst fears ??. It had seized!. We were on the outgoing tide so I quickly dropped the 6hp aux down and it started 1st pull ?. Whew.
Once back on dry land my immediate thoughts (I?m an engineer) were how and why with reference to the seizure. Actually, thinking about it, I can answer a lot of my own questions here. I guess the first clue is that last time I went out it stalled a couple of times at idle when in gear (at the time I put this down to the idle speed being too low) so I guess it was only firing on 2 & half cylinders. Also, now that I have carefully looked through the boat history receipts, I see that the last service by the Johnson dealer details that the impeller and impeller housing were both changed due to heat damage. The third clue is a little more subtle. I removed the plugs and it was No3 that had seized with plenty of metal shavings visible through the spark plug hole. I then decided to remove the head to inspect the damage further and noted that one of the lower head bolts for No3 pot had been sheared off level with the head and the other bolts in this area showed signs of being ?spannered? whereas the rest of the head bolts still had all the original paint on ! I would say it had been like this for some time. Another side issue is that it was also documented that the VRO had been bypassed about 18 months due to the engine badly smoking . I understand this mod is not uncommon and it had been running on premix. I have only used TCW3 but last owner may not have done. To be fair, the oil in the old VRO tank is blue so I guess it is a TCW oil.
I am guessing that at some time No3 has suffered heat damage and finally a ring has picked up on the bore, however, I would have expected it to have happened to No1 as No3 is the lowest cylinder.
Once I finally get the head off then I can ascertain the damage, however, a couple of questions,
I notice that people often rebore just one cylinder on an outboard ? On the car engines I normally rebuild this would be unthinkable. I would probably go down the route of a complete (all three) CNC rebore and then having the cylinders CNC plateau honed to alleviate any break in issues.
Whilst I rebuild a lot of Classis car engines (mostly American 1980?s V8?s) 2 stroke marine engines are new territory for me so I guess I will be looking at a lot of corrosion in the cooling system, but how much is acceptable if I am looking for another 5 years of trouble free service ? What other issues am I likely to come across ? When I rebuild is it worth going back to the VRO (OMC) oil system with a new pump ?
I am hoping this will make a nice winter project ready for next spring
Once back on dry land my immediate thoughts (I?m an engineer) were how and why with reference to the seizure. Actually, thinking about it, I can answer a lot of my own questions here. I guess the first clue is that last time I went out it stalled a couple of times at idle when in gear (at the time I put this down to the idle speed being too low) so I guess it was only firing on 2 & half cylinders. Also, now that I have carefully looked through the boat history receipts, I see that the last service by the Johnson dealer details that the impeller and impeller housing were both changed due to heat damage. The third clue is a little more subtle. I removed the plugs and it was No3 that had seized with plenty of metal shavings visible through the spark plug hole. I then decided to remove the head to inspect the damage further and noted that one of the lower head bolts for No3 pot had been sheared off level with the head and the other bolts in this area showed signs of being ?spannered? whereas the rest of the head bolts still had all the original paint on ! I would say it had been like this for some time. Another side issue is that it was also documented that the VRO had been bypassed about 18 months due to the engine badly smoking . I understand this mod is not uncommon and it had been running on premix. I have only used TCW3 but last owner may not have done. To be fair, the oil in the old VRO tank is blue so I guess it is a TCW oil.
I am guessing that at some time No3 has suffered heat damage and finally a ring has picked up on the bore, however, I would have expected it to have happened to No1 as No3 is the lowest cylinder.
Once I finally get the head off then I can ascertain the damage, however, a couple of questions,
I notice that people often rebore just one cylinder on an outboard ? On the car engines I normally rebuild this would be unthinkable. I would probably go down the route of a complete (all three) CNC rebore and then having the cylinders CNC plateau honed to alleviate any break in issues.
Whilst I rebuild a lot of Classis car engines (mostly American 1980?s V8?s) 2 stroke marine engines are new territory for me so I guess I will be looking at a lot of corrosion in the cooling system, but how much is acceptable if I am looking for another 5 years of trouble free service ? What other issues am I likely to come across ? When I rebuild is it worth going back to the VRO (OMC) oil system with a new pump ?
I am hoping this will make a nice winter project ready for next spring