2004 25 HP 4 Stroke RPM Reduction mode or?

[chiefdano82]

My first post here. thanks for reading.

I have a 2004 25 HP 4 stroke that I've had for about a year, electric start non-tiller model, no gauges whatsoever, and I am not sure if the alarm system works. I've never heard it come on or seen the light come one on the owl. It ran great up until 2 weeks ago.

I put in at the ramp, idled out, and I was running on plane for about 10-15 minutes when it starting to drop RPMs and I looked back to see smoke pouring off. Burning oil smoke. I shut it down and pulled the cowl. The oil filler cap had worked itself lose and come off. A decent amount of oil had come out and onto the block and inside the cowl. I got towed back to the ramp and went home. I drained about 1 qt of oil from it, replaced with new oil and filter, and tighten the oil cap like it was going out of style. I took it out yesterday for a test run and it would not get above a fast idle. Good water pressure (new impeller last month). Always new non ethanol fuel in a portable 6 gal tank. Ball is firm. Plugs are about a year old.I couldn't compression test it as I didnt have the correct size adapter.

I did put a 9.9x11 propeller on it when I replaced the oil, it used to have a 9.9x9.

I did a google search and a search here, but I think my search skills are lacking. I get a lot of results for bigger yamahas.

Thank you in advance.

[99yam40]

how much oil does that motor hold?
could the oil level got so low that it hurt the motor?

overheat and low oil pressure can cause RPM reduction

[chiefdano82]

how much oil does that motor hold?
could the oil level got so low that it hurt the motor?

overheat and low oil pressure can cause RPM reduction

2 qts, 1.9 I think to be exact. So i lost a qt when the cap backed off.

If it is in low rpm mode still, i suppose it still thinks its low on oil

[99yam40]

need to find out if there is low oil pressure ,I do not think it has any way to know what the oil level is, just pressure

[chiefdano82]

I went through the carb and fuel pump yesterday to see if they were not working properly. All seems good. No varnish and the fuel lines and inline filter seem fine. It is getting fuel as far as I can tell. I might put the old prop back on and try that, but an increase in pitch from 9 to 11 doesn't sound like it would cause the low RPM issue, to me at least. But I am no expert, unfortunately.

[99yam40]

did you read my last post on oil pressure?

need to find out if there is low oil pressure ,I do not think it has any way to know what the oil level is, just pressure

[chiefdano82]

did you read my last post on oil pressure?

need to find out if there is low oil pressure ,I do not think it has any way to know what the oil level is, just pressure

Yes I did. And it was what I was alluding to in my post before that. I didnt see anything that looked like an oil pressure sensor, but then again I wouldnt know what one looks like. Anyway to bench test that?

Edit: i found the sensor via the parts diagram

[99yam40]

tee in a pressure gauge to see what the pressure is
Not sure how the pressure sensor should read when tested , but I am sure service manual would say

[chiefdano82]

Prop change made no difference. Planning to check the sensor tomorrow

[chiefdano82]

An update:

After 3 months at the shop, the timing was fixed and a bearing was found bad. The first run it still made no power, so I took it back to the shop and they then found the carb was leaking and they rebuilt it. The shop also said the compression was perfect on both cylinders. About $1000 later and a lot of frustration with this particular shop, the boat ran good for about 30 minutes and then lost power for the rest of the day. However, this time it didn't lose all power, I'd say about 25%. For example, it would run 25 mph for the first 30 minutes and then it would not get over 18 mph, all things being equal. Starts and idles fine. I do not want to take it back to the shop as I have zero faith in them despite the great recommendations and reviews it has. And before I take it somewhere else and spend more money, I want to check a few things myself.

So, after a couple of thoughts from others, I checked the coil. Primary ohms were 0.5, pulse coil was 344 ohms, but secondary was 14.5K ohms. I do not know if the numbers I found online are correct, but for a 2004 25 HP 4-S Yahama F25 TLRC, it should be 4.1K, +- 10%. This is interesting.

I will check the spark or just flat out replace the plugs today and see if I can get another fuel primer bulb and check that this week. Always fresh non-e gas is used, too.

[99yam40]

what was wrong with the timing? and how did they fix it?
what bearing was bad?
was the bearing bad because of low oil pressure?
was there low oil pressure?

if you plan on working on it yourself find a service manual for your motor

[chiefdano82]

what was wrong with the timing? and how did they fix it?
what bearing was bad?
was the bearing bad because of low oil pressure?
was there low oil pressure?

if you plan on working on it yourself find a service manual for your motor

He stated the timing was "off" and they set it back to specs. I dont know more than that.
One of the crank bearings was starting to go bad and had some scoring on the crank it self. New bearing and a polish on the crank. He believes the bearing had been bad for some time, but also didnt rule out the loss in oil as a cause. Oil pressure was good as well.

[chiefdano82]

Update:

The 14k reading on the secondary coil didnt sit right with me so I went out and checked it gain this morning and it is reading within range at 4.6k. I think before I checked it with the plug boots on. My fault.

So I am back to a fuel problem or timing, again.

[chiefdano82]

I swapped the fuel tank, line, and ball. New fuel filter and plugs.

Same issue after 1 hour it loses power. Even worse this time. It won't get over 10mph.

[panasonic]

You said earlier you did not know if the alarm system worked on the engine. It has two lights on the cowling, correct? These little LED lights are known to burn out and they look like they are fine. You can test the lights themselves with a AA battery if I remember correctly.

Also it is easy to test the alarm system. With the engine running you unplug one of the wires from the over temp sensor or oil pressure sensor and ground it to the block...after a period of time the appropriate light will come on and the engine will go into RPM reduction mode.

I am not 100% that this is your setup but it is on the F15 of the same vintage as your engine. They are very similar.

If you knew that the alarm system works then that would help in your trouble shooting. Do you have the proper Yamaha manual?
I will look and see if I do.