Good Morning All,
I have two strange engine issues I am hoping someone might have some insight on for our Universal M-25XPB. To give a little background, we have done some decent work to the engine over the last few months. This includes replacing the heat exchanger, raw water pump, freshwater pump, themostat, coolant flush, replacing the alternator, new dripless adapter, new cutlass bearing, checking the engine alignment, checking and painting the engine mounts, cleaning and painting the block along with the typical fluid, filter and belt changes.
Let's start with the alternator. Factory the boat comes with a 51 amp Motorola alternator. My factory alternator had failed 7-8 years ago, it had about 250 hours of use on it. I found the same part number cross referenced to the same alternator used on Mercruiser engines and could be bought for around $75. I didn't expect much from these cheap alternators but my first one lasted 5-6 years, about 600 hours of use. It failed while we were in the Bahamas, but I had bought another as a spare before we left to go cruising and just swapped it out. The spare lasted until about May of this year and then it died, so about 2-3 years, about 900 hours of use. I bought two more of these cheap ones and put one on. The first of this batch died this past weekend, so about 3 months, 50-60 hours of use. Nothing has changed that I am aware, but going through 2 alternators in 3 months has me a bit concerned.
Just a little background on my setup. I have a 4 AWG wire going from the output of the alternator to a service switch (Blue Sea Systems M-Series 6006) and then to the primary bank with an ANL fuse. The primary bank is four Trojan GC batteries in series and parallel for a 450 Ah bank. The bank was very low, about 55% SOC, when I started the engine and this last alternator blew after running for about 3 hours. Everything is working fine with the new alternator (the second from this batch of cheap ones) but I am probably going to go with a high output external regulated alternator before we leave STT to go cruising again. I want to make sure I'm not missing something that will damage a good, expensive alternator. I plan to take the blown alternator to a local shop to have them look at why it blew. So any suggestions on something I am missing or not checking?
My second problem is related to the engine. One issue with the new alternators is that I do need to adjust the tach. I haven't done that yet. But with the original alternator I would get to about 3,400 RPM in neutral full throttle, currently I am reading 2,600 but with the same sound and a little bit of black smoke when I go full throttle in neutral. When ever I leave the mooring I will go full throttle for a little bit (1-2 minutes) once heated up to "blow it out". This weekend we ran over to St. John for the long weekend. I didn't have any issues, motored (going to STJ form STT is dead into the trades and current) at 2,000 RPM for 3 hours with no issues. We were making between 5-6 knots over water (only 3.4 knots over ground at times because of the aforementioned trades and current), no a nice comfortable cruising speed for our boat at about 80% throttle. Temp was perfectly steady at 160 degrees. However when I did my full throttle it would go up to about 2,400 RPM, stay there for about 30 seconds and then rev down to about 2,000 RPM and stay there. I would bring the throttle down to 2,000 RPM (so no change except for throttle position) after about 30 seconds I would bring it back up to 2,400 RPM with the same result. It never stalled and never reved down below say 1,800 RPM. Fuel filter looked fine and is relatively new (about 20 hours) and the bottom and prop are spotless (just hauled last month and had dove to clean the prop before we left). On the mooring in neutral it didn't have this issue. I would go to full RPM and it would stay there. So any thoughts?
Thanks
I have two strange engine issues I am hoping someone might have some insight on for our Universal M-25XPB. To give a little background, we have done some decent work to the engine over the last few months. This includes replacing the heat exchanger, raw water pump, freshwater pump, themostat, coolant flush, replacing the alternator, new dripless adapter, new cutlass bearing, checking the engine alignment, checking and painting the engine mounts, cleaning and painting the block along with the typical fluid, filter and belt changes.
Let's start with the alternator. Factory the boat comes with a 51 amp Motorola alternator. My factory alternator had failed 7-8 years ago, it had about 250 hours of use on it. I found the same part number cross referenced to the same alternator used on Mercruiser engines and could be bought for around $75. I didn't expect much from these cheap alternators but my first one lasted 5-6 years, about 600 hours of use. It failed while we were in the Bahamas, but I had bought another as a spare before we left to go cruising and just swapped it out. The spare lasted until about May of this year and then it died, so about 2-3 years, about 900 hours of use. I bought two more of these cheap ones and put one on. The first of this batch died this past weekend, so about 3 months, 50-60 hours of use. Nothing has changed that I am aware, but going through 2 alternators in 3 months has me a bit concerned.
Just a little background on my setup. I have a 4 AWG wire going from the output of the alternator to a service switch (Blue Sea Systems M-Series 6006) and then to the primary bank with an ANL fuse. The primary bank is four Trojan GC batteries in series and parallel for a 450 Ah bank. The bank was very low, about 55% SOC, when I started the engine and this last alternator blew after running for about 3 hours. Everything is working fine with the new alternator (the second from this batch of cheap ones) but I am probably going to go with a high output external regulated alternator before we leave STT to go cruising again. I want to make sure I'm not missing something that will damage a good, expensive alternator. I plan to take the blown alternator to a local shop to have them look at why it blew. So any suggestions on something I am missing or not checking?
My second problem is related to the engine. One issue with the new alternators is that I do need to adjust the tach. I haven't done that yet. But with the original alternator I would get to about 3,400 RPM in neutral full throttle, currently I am reading 2,600 but with the same sound and a little bit of black smoke when I go full throttle in neutral. When ever I leave the mooring I will go full throttle for a little bit (1-2 minutes) once heated up to "blow it out". This weekend we ran over to St. John for the long weekend. I didn't have any issues, motored (going to STJ form STT is dead into the trades and current) at 2,000 RPM for 3 hours with no issues. We were making between 5-6 knots over water (only 3.4 knots over ground at times because of the aforementioned trades and current), no a nice comfortable cruising speed for our boat at about 80% throttle. Temp was perfectly steady at 160 degrees. However when I did my full throttle it would go up to about 2,400 RPM, stay there for about 30 seconds and then rev down to about 2,000 RPM and stay there. I would bring the throttle down to 2,000 RPM (so no change except for throttle position) after about 30 seconds I would bring it back up to 2,400 RPM with the same result. It never stalled and never reved down below say 1,800 RPM. Fuel filter looked fine and is relatively new (about 20 hours) and the bottom and prop are spotless (just hauled last month and had dove to clean the prop before we left). On the mooring in neutral it didn't have this issue. I would go to full RPM and it would stay there. So any thoughts?
Thanks
