2005 Honda BF150 RPM limited, no alarms

I have a 2005 BF150 I bought new and it has been a flawless motor until now. The engine planes off and runs a normal cruise rpm for about 10 minutes, then the computer limits the Rpms to about 2000 rpms (I don't remember exactly what rpm it is reduced to. There is no alarm. The only light on is the green oil light. The engine has a new water pump and thermostats. Any help is greatly appreciated!

Have you downloaded any codes?

I do not have a way to read codes other than taking it to the dealer, which is a hassle. Is there an easy way to read them without purchasing 1000 dollar software?

The most helpful thing to me would be knowing what will limit the rpm of the motor and not trigger an alarm on this particular engine. Temperature? Anything else?

Have you tested telltale stream"pisser" temperature,you should be able to keep hand in there indefinitely, Are heads getting hotter than normal? Can you hold your hand on either head for a 6 second count,without scolding yourself. Engine is in limp mode,usually half the cylinders are cut out by computer, Lack of oil flow,oil pressure drop,lack of fuel flow,could possibly trigger this, Hondadude is the expert on these engines wait for his response

In this regard, I think the 150 is like the 200 and 225. The only two things that automatically bring the engine down to 1800 rpm's is oil pressure and overheat. If overheat, it will drop down to 1800 rpm for 20 seconds. If the overheat is not resolved in that time, it shuts down. If low oil pressure, it will drop down to 1800 rpm and continue to run at 1800. Either one of those situations should trigger an alarm, at least it does on the 200/225. It seems like with the green oil pressure light staying lite when the engine rpm's drop down, then that points to an overheat situation. As Johnny implied, check the heads and manifolds. Best to do that with an IR heat gun. They are cheap and useful for lots of things. If I were in your position, the first thing I would check would be the new thermostats and make sure the water pump was installed correctly. If I recall correctly, the 150 has two thermostats that are different from each other. Is it possible that they were installed incorrectly? Put the t-stats in a pan of water on the stove and make sure they open when heated up. They don't open very far. On the 225, they only open 3 mm. Again, if I recall correctly, one of those t-stats opens at a different temperature than the other one.

I believe the procedure for pulling codes on the 150 is the same as the 200/225. Pull the engine cover, remove the cover over the electronics, and find the red four-prong service connector. Shunt the lime green and black wires with a paper clip. Turn on your ignition and count the number of long and short blinks on the MIL (check engine) light. The codes for the 150 are different than the 225, so I can't tell you what they mean. Hopefully someone else will post them.

Excellent info!! I will use this method to pull the codes today! It is very strange that there is no alarm, but the alarm does seem to be working properly.

If you have the four-light key switch, which you should, when you first turn on your key, make sure all four lights blink on and off. The red alternator light should then stay on until you start the engine, then it will go off and the green oil pressure light should come on and all the three red lights should be off.

So I've doing a little running around now that I have secured a seasonal moorage on Fishermans Bay, Lopez Island, Wa (2 miles from my year round home. I took the (1989 Seasport Skipper, Hvy duty fiberglass, Cabin style, 4300 lb , 19' w/ bracket , Honda 150 main and a 15 hp kicker ) boat out today and did some runs. It seams to like 26 mph @ 4400 rpm, goes fine at 31 mph / 5000 rpm, and will do 54-5500 rpm / 35 mph. I have a 15 1/2 x 17 SS prop on it now ---- chat do you think of the performance.

My first outboard boat
Jimmy

I would be looking at your fuel system, if there is no alarm there will be no faults. Sounds like fuel starvation to me if rpm is dropping so much