Start with basics, is the tachometer working properly; is it consistent on its readings whether in neutral or in gear. What speed are you getting at 1900 RPM? Are the boat's bottom and prop clean? Check the valves lash. Is the engine smoking, and if what color? When running the engine at idle and at medium RPM, remove the oil filler cap and place the palm of your hand about an inch above the opening, if you feel a strong back pressure, that would be compression leaking through the piston rings into the crankcase creating pressure (sign of a worn engine) A little heavier oil could help with that. Also check the condition of the fuel. It does not necessarily has to be a serious failure but just mentioned a few things or combination of that could cause your problem.
Low Power/RPM Universal M25XP
- Thread starter jonelli
- Start date
Well, a month has passed, yes. I’ve spent about 4-5 different days at the boat, done all my maintenance, removed the counter, replaced a rotted exhaust. I will check the strainer in the pump. I don’t really know what I’m checking behind that without specific info.
I thought that I put that info in your other thread (could have been someone else's thread), but here is a basic test procedure.
I'm going to assume that you don't have a pressure gauge or know the specs for the pump.
1. Purchase about 10 feet of fuel hose.
2. Hook one end fuel hose to the output of the pump.
3. Take the loose end of the hose and place it into a quart jar or a coffee can.
4. Place the jar/can about 6 feet above the pump, up on deck will work.
5. Run the pump and monitor the discharge. Use a stopwatch. How long did it take to pump 1/2 quart?
Without looking up the pump specification, my best guess is that it should take less that 1 minute to pump 1/2 quart. The idea here to to make sure the pump has pressure and volume.
I'm going to assume that you don't have a pressure gauge or know the specs for the pump.
1. Purchase about 10 feet of fuel hose.
2. Hook one end fuel hose to the output of the pump.
3. Take the loose end of the hose and place it into a quart jar or a coffee can.
4. Place the jar/can about 6 feet above the pump, up on deck will work.
5. Run the pump and monitor the discharge. Use a stopwatch. How long did it take to pump 1/2 quart?
Without looking up the pump specification, my best guess is that it should take less that 1 minute to pump 1/2 quart. The idea here to to make sure the pump has pressure and volume.
You gave me the general description of what to do but this is more clear. Thanks. I’ll try this today.
No. I filled up before leaving. Went to the isthmus, rpms normal, fished a little and that’s when I noticed low rpm. spent the night, went under boat in morning to check prop, it looked clear. motored and fished the next day all the way around the west end to Cat harbor, spent the night and motor sailed home the next day. The rest of the trip was WOT to get close to 2K RPM. No heating issues. Guessing approximately 12-14 hours of motoring total and used up pretty much 75% of fuel. It definitely seemed a lot more than usual. I don’t always use it like a motor boat, but I’ve got a couple buddies that like to fish.
anyway, I’ve checked all I can check for now.
I’m going to take her out tomorrow morning and run her around and see how she behaves.
Maybe I misunderstood your question. Yes I filled up with fresh fuel before my last trip.
I just put more fresh fuel in recently.
My usual is to take my 6 gallon jerry can to a local gas station and save $1.50/gallon.
Took her out this morning.
motor sounds good. Still can’t get to top RPMs but it went a little further than before. So after everything I did, it would get JUST to 2100 WOT.
no overheating. The throttle cable is hitting the max stop point, no smoke but the tiniest bit of white.
I noticed going back into the slip that going from forward to reverse seemed very slow and laggy in power. It didn’t feel normal. It was weak building up power to reverse thrust.
I’m about to give up and think I need to call somebody. I’m running out of time to work on it myself. And I’m running out of diy things to do.
motor sounds good. Still can’t get to top RPMs but it went a little further than before. So after everything I did, it would get JUST to 2100 WOT.
no overheating. The throttle cable is hitting the max stop point, no smoke but the tiniest bit of white.
I noticed going back into the slip that going from forward to reverse seemed very slow and laggy in power. It didn’t feel normal. It was weak building up power to reverse thrust.
I’m about to give up and think I need to call somebody. I’m running out of time to work on it myself. And I’m running out of diy things to do.
My point is, if there is some kind of clog in your tank or in the fuel pickup tube or some other thing of that sort, using a temporary, portable fuel tank that you know is clean would eliminate that issue as opposed to just pouring more fuel into a possibly dirty tank.
Really hard actually. It’s like it’s starving. Once it turns and you can hear the compression igniting, I have to hold the starter for a little while longer or it will just die immediately. Almost kind of like if you haven’t started it for months or something.
but it’s every time. Even if you just ran it an hour ago.
Before I go do that test, the fact the pump put out 12 ounces in 23 seconds wouldn’t matter? If there was a flow problem in the lines before the pump, wouldn’t the pump not be able to do it’s job? So, how would feeding a jerry can of fresh fuel into the pump be different?
I have seen hose/line fail internally. They delaminate and collapse internally, cause restriction & check valves.
I've seen it happen on brake lines and on my own lawnmower (drove me nuts).
I've seen it happen on brake lines and on my own lawnmower (drove me nuts).
A few more ideas.
1. Check the glow plugs & relay operation. Why, its easy and that could be the cause of the starting difficulty.
2. Pull the glow plugs and do a compression test.
3. Pull the injectors and have them tested.
4. Check the compression release lever and make sure that it is not partially engaged.
1. Check the glow plugs & relay operation. Why, its easy and that could be the cause of the starting difficulty.
2. Pull the glow plugs and do a compression test.
3. Pull the injectors and have them tested.
4. Check the compression release lever and make sure that it is not partially engaged.
I would try the portable tank test anyway. It's different because you were not actually connected to the engine and the fuel demand is not the same. This is easy and easy test to do so why wouldn't you? It would tell you if it is a bad fuel/blockage problem or something else. I really don't think the test you did with the pump tells you that.
For me this a fuel pickup clogged mesh. RPM goes from 1900 to 2100 for no apparent reason, short pump check delivers satisfactory results etc.
Crud in the bottom of the tank accumulates WITH TIME on the pickup mesh. No flow, no crud accumulates. Engine stopped, crud falls back on the bottom. Little pumping, just a little crud accumulates.
So first thing to do is test with clean fuel from a different tank, this will confirm/infirm the clogged mesh hypothesis.
