lewisgaines
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- Joined
- Jun 19, 2020
- Messages
- 2
Hey guys,
TLDR: I ran the boat recently and while at full throttle it lost power and the alarm sounded. I replaced the oil and cranked it in the driveway and the alarm came back on after ~30 seconds. I think there might be a problem with the output of the water pump getting to the engine but I don't know if that is the cause of the alarm or just something I happened to find.
I recently replace my Mercury 9.9 with a new 25, and I've have been running it without issue for a while. I've put probably 5-6 hours over a few weeks just fine until last weekend. I was out on the lake and running the motor at pretty much wide open when I felt "something". It seemed like the boat just lost power and then the oil light and alarm sounded (engine still running). I brought the throttle back down to idle then killed the engine. I let it sit for a few minutes before starting it back up. About 30-45 seconds after starting the alarm came back on so I killed the engine, got a tow back to the marina and brought it home. The next day I checked the oil and it seemed full, if not slightly over-filled. The guy I bought it from, a boat mechanic, changed the oil and water pump impeller right before I before I bought it. I went ahead and replaced the oil and I made sure it was filled with exactly the right amount. The old oil seemed a little dark but not the worst I've seem, but also seemed slightly thin (Although that could have just been in my head). After the oil change I hooked the hose up and cranked the engine in the driveway which, again, ran for 30-45 seconds before the alarm sounded.
Things I'd like to note:
- The water pump output pressure has always seemed very low to me since I bought it. The 2000 Mercury 9.9hp 4-stroke I had previously shot the water out with a good amount of force, but this only seems to have an "ok" flow at pretty lousy pressure.
- It didn't have a prop when I bought it and I didn't know exactly with what I needed to replace it. I did the prop size calculators and bought something I thought was reasonable. I don't know exactly what rpm it is running at when wide open, but the motor seems fairly quiet and not strained so I don't think I'm going over the recommended RPM limit, but I obviously can't say for sure.
- I never really felt the temp of the cooling water output when running the motor at full throttle out on the lake so I can't give a good answer to whether I thought it was running hot or not.
At this point I decided to double check the water pump condition to make sure there wasn't something obvious that could be causing the low cooling water output flow and to make sure the guy I bought it from didn't out-right lie to me. The impeller looked new, minus the minimal wear from the hours I had put on it. Then I noticed there was a lot of scale on the walls of the drive gear housing where the copper water tube sends water up to the engine. I honestly don't know if that should be a dry compartment or if it does fill with water, but what I saw next makes me think it was the latter. The copper tube that sends water from the pump to the engine has a somewhat odd end. For reference it is part 33 on the diagram in the link I have attached. I have also attached an image that shows my end of that tube as well as the scale inside the gear housing compartment. I know that the tip should angled and almost look like the tip of a hypodermic needle, but I'd be terrified if the tip of the needle going in me looked like this thing. I don't know what damaged the end of the tube, but my suspicion is that there is a leak between the tube and the water pump output seal. This is causing the compartment to fill with water and result in the low water output pressure.
So here are my questions:
1. What are the reasons the light on the motor could/would illuminate and the alarm sound? Is it only for low oil pressure, or does it also alert for over-temp or over-rpm?
2. Am I totally off base with the water pump tube and scale build-up in the gear housing?
3. Did the lack of flow and thus potentially an engine running hot cause permanent damage or at least damage I could check for?
4. Does anyone know the factory resistance of the oil pressure sensor so I might be able to test if it is faulty?
5. Are there any generic (or specific) steps I could walk through to determine the cause of the alarm?
Please let me know if there is any more info I can fill in or details I can provide.
Thanks a lot in advance,
Lewis
TLDR: I ran the boat recently and while at full throttle it lost power and the alarm sounded. I replaced the oil and cranked it in the driveway and the alarm came back on after ~30 seconds. I think there might be a problem with the output of the water pump getting to the engine but I don't know if that is the cause of the alarm or just something I happened to find.
I recently replace my Mercury 9.9 with a new 25, and I've have been running it without issue for a while. I've put probably 5-6 hours over a few weeks just fine until last weekend. I was out on the lake and running the motor at pretty much wide open when I felt "something". It seemed like the boat just lost power and then the oil light and alarm sounded (engine still running). I brought the throttle back down to idle then killed the engine. I let it sit for a few minutes before starting it back up. About 30-45 seconds after starting the alarm came back on so I killed the engine, got a tow back to the marina and brought it home. The next day I checked the oil and it seemed full, if not slightly over-filled. The guy I bought it from, a boat mechanic, changed the oil and water pump impeller right before I before I bought it. I went ahead and replaced the oil and I made sure it was filled with exactly the right amount. The old oil seemed a little dark but not the worst I've seem, but also seemed slightly thin (Although that could have just been in my head). After the oil change I hooked the hose up and cranked the engine in the driveway which, again, ran for 30-45 seconds before the alarm sounded.
Things I'd like to note:
- The water pump output pressure has always seemed very low to me since I bought it. The 2000 Mercury 9.9hp 4-stroke I had previously shot the water out with a good amount of force, but this only seems to have an "ok" flow at pretty lousy pressure.
- It didn't have a prop when I bought it and I didn't know exactly with what I needed to replace it. I did the prop size calculators and bought something I thought was reasonable. I don't know exactly what rpm it is running at when wide open, but the motor seems fairly quiet and not strained so I don't think I'm going over the recommended RPM limit, but I obviously can't say for sure.
- I never really felt the temp of the cooling water output when running the motor at full throttle out on the lake so I can't give a good answer to whether I thought it was running hot or not.
At this point I decided to double check the water pump condition to make sure there wasn't something obvious that could be causing the low cooling water output flow and to make sure the guy I bought it from didn't out-right lie to me. The impeller looked new, minus the minimal wear from the hours I had put on it. Then I noticed there was a lot of scale on the walls of the drive gear housing where the copper water tube sends water up to the engine. I honestly don't know if that should be a dry compartment or if it does fill with water, but what I saw next makes me think it was the latter. The copper tube that sends water from the pump to the engine has a somewhat odd end. For reference it is part 33 on the diagram in the link I have attached. I have also attached an image that shows my end of that tube as well as the scale inside the gear housing compartment. I know that the tip should angled and almost look like the tip of a hypodermic needle, but I'd be terrified if the tip of the needle going in me looked like this thing. I don't know what damaged the end of the tube, but my suspicion is that there is a leak between the tube and the water pump output seal. This is causing the compartment to fill with water and result in the low water output pressure.
So here are my questions:
1. What are the reasons the light on the motor could/would illuminate and the alarm sound? Is it only for low oil pressure, or does it also alert for over-temp or over-rpm?
2. Am I totally off base with the water pump tube and scale build-up in the gear housing?
3. Did the lack of flow and thus potentially an engine running hot cause permanent damage or at least damage I could check for?
4. Does anyone know the factory resistance of the oil pressure sensor so I might be able to test if it is faulty?
5. Are there any generic (or specific) steps I could walk through to determine the cause of the alarm?
Please let me know if there is any more info I can fill in or details I can provide.
Thanks a lot in advance,
Lewis
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