Sergio Uribe
Cadet
- Joined
- Mar 4, 2013
- Messages
- 10
In my boat, there are two Mercruiser 4.3LH engines, with Bravo III outdrives.
When I first start the engines, and after letting the engines warm up, I then push the throttles to reach cruising speed, and let's say I stabilize the engines at 3600 RPM. The engines are showing normal temperatures, and oil pressure. After cruising for about 35 minutes, suddenly the right engine starts loosing RPMs, and if I leave the throttle where it was, the RPMs would go down and finally the engine will stop. But if I pull the throttle down to minimum, the engine would not stop, and continue running at such minimum RPMs. (I have to pull the other engine down, because the boat would not continue cruising with only one engine). If I then wait for about 5 to 10 minutes, then I could bring the two engines back to cruising speed, but the loss of RPMs of the right engine would come after a time shorter of the 35 minutes of the first failure. If all of the procedure is repeated, the third loss of RPMs comes after a shorter time, and so on.
If all of the above procedure is done but stabilizing the engines the first time at about 4200 RPMs (instead of 3600), the first loss of RPMs would come after cruising for about 25 minutes (instead of 35).
If all of the above procedure is done but stabilizing the engines the first time at about 3400 RPMs (instead of 3600), the first loss of RPMs would come after cruising for about 40 to 45 minutes (instead of 35).
The question is simple: what is wrong, and causing such strange operation ot the right engine?
When I first start the engines, and after letting the engines warm up, I then push the throttles to reach cruising speed, and let's say I stabilize the engines at 3600 RPM. The engines are showing normal temperatures, and oil pressure. After cruising for about 35 minutes, suddenly the right engine starts loosing RPMs, and if I leave the throttle where it was, the RPMs would go down and finally the engine will stop. But if I pull the throttle down to minimum, the engine would not stop, and continue running at such minimum RPMs. (I have to pull the other engine down, because the boat would not continue cruising with only one engine). If I then wait for about 5 to 10 minutes, then I could bring the two engines back to cruising speed, but the loss of RPMs of the right engine would come after a time shorter of the 35 minutes of the first failure. If all of the procedure is repeated, the third loss of RPMs comes after a shorter time, and so on.
If all of the above procedure is done but stabilizing the engines the first time at about 4200 RPMs (instead of 3600), the first loss of RPMs would come after cruising for about 25 minutes (instead of 35).
If all of the above procedure is done but stabilizing the engines the first time at about 3400 RPMs (instead of 3600), the first loss of RPMs would come after cruising for about 40 to 45 minutes (instead of 35).
The question is simple: what is wrong, and causing such strange operation ot the right engine?
