Mercury 40 classic rev limit? limp mode?

[hewittrd]

I am new to the outboard engine. I bought a 1996 Mariner 40 classic (4 cyl) last month. I ran the boat for at least 10 hours since then. It has run like a dream until last night.

Of course, I was doing some late catfishing and they were bighting. I didn't want to leave. Just before dark,I decided to go home and the engine ran fine for a couple of minutes. Got on plane great and ran 1/4 mile down the river then just slowed down. I was going just over idle speed in the pitch dark, about 5 knots not on plane. Took forever to get home.

It "pee's" just fine. I tried to run it today and it is limited right from the start (cold engine). No trouble starting (started on second pull). It seems like some sort of rev limiter. I don't know if there is a limp mode on a 40 classic and if there is one, how do I reset it or get it to run again.

Thanks for the help in advance.

 

[hewittrd]

Re: Mercury 40 classic rev limit? limp mode?

If it helps, the boat (15 ft War Eagle) won't get on plane under the current power.

The throttle arm seems to be two stage. The first stage hits a stop (govenor) then the second arm is activated by the throttle cable. It seems that the second throttle arm isn't working. Not sure, but I am trying to send out all the information I can so I may have a chance to learn and fix this motor.

Thanks again.

 

[hewittrd]

Re: Mercury 40 classic rev limit? limp mode?

Lets keep this thing going. I know a little about engines, just not 2 cycle. I can find the carbs, block, head, plugs, ignition system, and the hose that leads to the "pee" hole. I can't find the thermostat. I think that there may be a fail safe sensor for the heat of the engine, but I can't find the sensor. Can anyone tell me where the thermostat is so I can take it out and flush the cooling system?

I know that there are alot of smart people who read these forums and I need to pick your brains a little.

 

[Faztbullet]

Re: Mercury 40 classic rev limit? limp mode?

I can't find the thermostat. I think that there may be a fail safe sensor for the heat of the engine, but I can't find the sensor.

Nope...... aint got either. Have someone advae throttle (engine off) and watch arm . The top of arm should stop and 2nd part opens the carbs. If the 2nd part does not more and open carbs(look in throat with flashlite) you have a problem with control box...

 

[hewittrd]

Re: Mercury 40 classic rev limit? limp mode?

Thanks for the reply. This engine uses a tiller handle. So I can look at the carbs while I operate the throttle. The top arm does stop and the second part moves past the first. I just checked and the circular flaps inside the carbs don't open, but the engine wasn't running at the time (it's getting late and don't want to wake the neighbors) so could be the choke holding them closed. I will test it out tomorrow morning and update.

This seems to be working. Any more suggestions if this isn't the problem that I can try tomorrow morning?

 

[hewittrd]

Re: Mercury 40 classic rev limit? limp mode?

Thanks for the information from faztbullet, I fixed the problem this morning. The second arm was moving but wasn't connected to the carbs. A piece of linkage had popped off. The carbs weren't being activated. A look in good light, armed with some knowledge and I fixed it in just a few minutes.
Thanks again!!! The fish can once again fear for their lives!