Mercury engine blew after running with hose on

[HTG]

I have a 1984 35hp Mercury that was running great until I ran it on high for a short time with just the water hose muff. The engine made a pop and now its not starting on the first crank like it was. I now have shift to neutral to get it to start. I'm wondering if I can fix it or if I will need to bring it to a mechanic. Anyone know what may fix this problem or get it back to starting on the first crank again?

 

[GA_Boater]

Three things;

1. "I ran it on high for a short time with just the water hose muff." On muffs, only run it at high idle. I don't know what running on high actually means, but 1500-2000 RPM is about as much as you want to run on muffs
2. "I now have shift to neutral to get it to start." Neutral is where you should start the motor and if you're starting in gear the neutral start switch is bad or bypassed.
3. "I'm wondering if I can fix it or if I will need to bring it to a mechanic." I don't think we can answer that.

Start with a compression test. It sounds like something inside the motor broke while running it too fast on muffs.

 

[HTG]

I ran it at full throttle with just the hose muff on. After that it sounded like something popped. Now I can't get it to start unless I put the gear button in and put the gear forward. I did a compression test and both were normal the lower was about 5lbs difference so I am still attempting to find out what else it could be.

 

[poconojoe]

I may not be able to help you, but please clarify. Does it run or not? You said you can't get it to start unless you press the "gear button" in. When you say start, do you mean crank only with no starting or does it actually run?

 

[roscoe]

And if it does still run, does it sound like it is running normally ?

 

[HTG]

It will run pretty good at full throttle most of the time. It dies out when slowing down to 1 to 5 MPH and at idle. I have had trouble docking it when that issue comes up, and occasionally it will die at other higher speeds and I have to pump the gas line. It also dies when going into reverse. I'm trying to figure out how many possibilities could be causing this before I start to figure it out or take it to a mechanic.

 

[GA_Boater]

You need to rebuild the fuel pump. That's why it runs when squeezing the bulb at high speed,

Don't run the motor at full throttle on muffs as there good chance of blowing it to smithereens.

 

[HTG]

I wonder if I can do it are there any videos on it? I'll check YouTube. I've replaced the starter and solenoid that wasn't to bad. I replaced the impeller, that took few days to get back together. Thank you, I appreciate it. Nice boat I have a 15ft 1971 yellow Starcraft. I like because it so light weight.

 

[poconojoe]

It's good that its running. I thought you said it was blown. This is good news!

 

[roscoe]

The "pop" noise was likely a backfire, which caused damage to the diaphragm in the fuel pump. Also need to look for cause of backfire, likely carb mixture too lean, may need adjusting or cleaning.

Fuel pump rebuild is easy. I suggest you get the kit directly from a Merc dealer.

 

[jimmbo]

Lucky that it didn't throw a rod through the crank case, or break a ring

 

[HTG]

While doing this is there anything else I can do to improve performance? The carburetor was cleaned about 6 seasons ago so it should be in pretty good condition. I'm not sure if that's something that I want to take off unless I have to. Thanks I appreciate it.

 

[ajgraz]

6 seasons? Carb cleanings on old America is a seasonal thing. Unless you’re running a fuel/water separating filter, then maybe every 2-3 seasons.

 

[ajgraz]

Edit, mercs somehow spell corrected to americas

 

[roscoe]

Inspect fuel line for deterioration inside.
If it is coming apart, it will plug the carb again and again and.....

 

[HTG]

Thanks, that's one thing I haven't thought about. I'll have to take the fuel line apart. Can anyone recommend a carburetor cleaning thread or video?