calboats
Seaman Apprentice
- Joined
- Jun 6, 2009
- Messages
- 41
With what I learned here, I managed to find that the top two cyl. on my EX-115 6cyl. Merc. were set by the dealer just enough lean that they slowly overheated at top throttle. I replaced the fuel pump twice, the coil once, and wondered what the problem was. Water pump tested out good, all to no avail. Water cooling to the top two on a straight six, is critical, but that showed a good strong flow.
My NEW mechanic says that the top carb was set just enough lean that when at top throttle the top 2 cyl. ran too lean by just a touch -- not very obvious. However since I did not catch that -- over a couple summers of running, every time I did full throttle starts, or carried a heavier load, it leaned out the top two cyl, misfired a little bit more each time, till it finally did the damage.
I wondered why it idled great, but started to misfire at full throttle and cough a bit. Sometimes it would just stop dead at cruise speed !!! Then in a few minutes it woud restart and run great again, maybe no problems for the rest of the day. To recap, it stopped for the final time on a warm lake in August, three guys aboard, on a high speed yahoo! Got drug in by a passing boat, and that was it. Smoking exhaust, the whole bit !!
Got a new mech, who privately does motors only, he took the Merc in on a fresh 1989 Evinrude 50, he had -- and a few dollars more. Sooo that's it, will be changing over soon. Since the boat was rated for 25 to 80 hp anyhow, the 115 was a bit much. Transom was pretty submerged with the 115 on a setback & jackplate. Don't need to do 40 mph cruise, at too many gal/hr.
Thanks once again, Cal See Ya on the "Rude" page !!
My NEW mechanic says that the top carb was set just enough lean that when at top throttle the top 2 cyl. ran too lean by just a touch -- not very obvious. However since I did not catch that -- over a couple summers of running, every time I did full throttle starts, or carried a heavier load, it leaned out the top two cyl, misfired a little bit more each time, till it finally did the damage.
I wondered why it idled great, but started to misfire at full throttle and cough a bit. Sometimes it would just stop dead at cruise speed !!! Then in a few minutes it woud restart and run great again, maybe no problems for the rest of the day. To recap, it stopped for the final time on a warm lake in August, three guys aboard, on a high speed yahoo! Got drug in by a passing boat, and that was it. Smoking exhaust, the whole bit !!
Got a new mech, who privately does motors only, he took the Merc in on a fresh 1989 Evinrude 50, he had -- and a few dollars more. Sooo that's it, will be changing over soon. Since the boat was rated for 25 to 80 hp anyhow, the 115 was a bit much. Transom was pretty submerged with the 115 on a setback & jackplate. Don't need to do 40 mph cruise, at too many gal/hr.
Thanks once again, Cal See Ya on the "Rude" page !!