1995 Mercury 135 won’t go higher than 2000 rpm WOT

[Jlockler]

Was out on the water a few weeks ago and my primer bulb split. I was able to run about 1/4 throttle to make it back to the ramp. Anything higher and motor would die. The next day I put a new bulb on and took it out for a spin, no issues was on the water all day long.

Unfortunately I was in the path of the recent hurricane Laura, we had minimal damage to our property but I haven’t been able to run the boat due to evacuation/clean up.

Today I took it out, it’s been around 3 weeks, It took a few turns to get it to turn over, finally did but idles a little rough and when you shift in gear sometimes it dies. Also had to keep the motor trimmed up slightly at idle. If I trimmed down as I would before going wide open it would die. At WOT it won’t go higher than 2000 rpm in forward. However in reverse or neutral it will rev up just fine. I let it run around 1500 rpm in neutral for a few minutes that didn’t help at all. The fuel is only a few weeks old. Not sure where to start trouble shooting, probably going to change the filter and check the anti-siphon valve tomorrow.

If anyone has experienced this before and could point me in the right direction that would be great. I would rather not have to shop my boat right now, money is tight with the recent hurricane.

 

[Chris1956]

Did the motor get submerged during the storm? Did the fuel tank get submerged during the storm. It could be as simple as water in the fuel.

Take a spark and compression test.

 

[Jlockler]

No we didn’t even get a much rain just winds and the boat was put in the garage. I’ll post results of compression and spark test later today.

 

[Jlockler]

Spark and compression have been tested and both check out. I ran it on the muffs again to see if I could replicate the issue out of water. Everything ran fine, however I did notice the tell tale stream was pretty hot, not scolding I could keep my hand under it just seemed hotter than I would expect. Also the starboard side cylinder bank runs hotter than the port side. Now I’m starting to wonder if there is a sensor that could have possibly put the motor is some sort of safe mode? Not even sure if my model has that, I’m just throwing stuff around. Seems to be a sensor on each cylinder bank just not sure which is what. I did check the thermostat on the starboard side and it looks pretty bad. Going to order new stats since they’re cheap and probably need to be replaced anyway. Maybe the hotter starboard cylinder bank tripped temp sensor and that’s what’s causing the rpm limit? the Still scratching my head on this one. Any help is appreciated.

 

[Dukedog]

Was out on the water a few weeks ago and my primer bulb split.

this is a tell-tale sign of fuel lines givin' up... they "all" need ta be changed.. i'd start with a good carb cleanin' and all new gaskets inside and out...

ya right, that motor does not have any kinda "safe mode" it either runs or it doesn't..........

tha "sensor in tha starboard head is for over temp alarm.. tha one in tha port head is for a "temp gauge".. they are different... neither will "limit" rpm.. stats won't either.

send me an email addy and i'll send ya an OEM manual for your motor in pdf...........

 

[Chris1956]

Your motor's cooling is controlled by the thermostats at low speed and the poppit valve at speeds higher than 2000RPM or so.

If the 'stats are bad, you should rebuild the poppit as well. Make sure you get the exact correct kit for your motor and year, as they have changed over the years.

 

[Jlockler]

Your motor's cooling is controlled by the thermostats at low speed and the poppit valve at speeds higher than 2000RPM or so.

If the 'stats are bad, you should rebuild the poppit as well. Make sure you get the exact correct kit for your motor and year, as they have changed over the years.

I sent you my email, any help would be great. Ill
look into changing the fuel lines and checking the fuel system components. Just had to go out of town for work but I’ll post results in a week or two once i get back.