Engine died Mercruiser 3.0 after about 20 minutes of running

viper1216

Chief Petty Officer
Joined
Jul 31, 2013
Messages
420
Hi All,

I just bought a boat about 2 weeks ago and have been going through it. Took it out on the pond for the first time last weekend. Seemed to be running great for about 20-30 minutes or so. I shut it down to take a look at the engine area to make sure everything looked ok...no leaks, all looked fine. Engine fired right up. Started off again...after about 3 minutes or so....engine power just didn't seem right...felt like it was losing some and engine had a light metallic pinging noise going on..went about another few minutes...and she felt like she was going to die...throttled back to just above idle to try and get back to the launch....temp gauge started to rise...was a little above 160...then engine quite and would crank but no start. Ended up getting towed in....tried starting a few times but never kicked over. After trailering and getting home...popped a couple of ears on it and she fired right up first crank. My buddy who was with me seems to think it over heated. I looked around the forum and some were saying 160 is the operating temp and others recommended making sure it didn't go over 200, which it didn't. Would the engine die with a temp just over the half way mark? On the agenda for tomorrow is a new impeller and T-stat, but I just wanted to see if anyone else had any idea for other things I could check.
Boat is an 88 as well as the engine.

Thanks
Dave
 

djmakko

Petty Officer 2nd Class
Joined
May 9, 2011
Messages
134
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

Hi All,

I just bought a boat about 2 weeks ago and have been going through it.
Dave

Define: going Thorugh it! What have you done to it.
 

bonzoscott

Senior Chief Petty Officer
Joined
Jul 26, 2008
Messages
745
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

Posted in the "Stickys" at top of forum is: Boatinfo - The library, containing manuals, brochures and other technical documents from the last hundred years!
Go there find your motor and: Your problem sounds more like starving for fuel. Verify the carb is pumping gas down the carb throat when pushing throttle. Inspect / replace all filters. Check / clean your anti-siphon valve at the tank. 160-180 is fine op temperature. I wouldn't rush to change impeller / pump although it is good maintenance on a boat of unknown history. Again, your temp is good and don't think it is causing your problem.
 

viper1216

Chief Petty Officer
Joined
Jul 31, 2013
Messages
420
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

Djmakko - So far I've changed the gear oil...replaced the fuel sending unit, new fuse holder for the horn and diagnosed and will be replacing the trim limit switch and sender.
Haven't done much engine wise as it seemed to run really well when at home and didn't run in to issues till it was on.

Bonzoscott - Thanks for the info, I will look in to the fuel issue. Would it really run fine, and then all of the sudden run like crap? Tough to diagnose the fuel issue with the Carb as it runs fine here, so I'm sure it's getting fuel. I would really like to try and figure out before I take it back out, I don't want to get stuck again. I'll start with the filters.
 
Joined
Jun 17, 2012
Messages
940
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

I'm thinking your problem may be ignition related. Possibly a bad HT lead sparking to ground. These problems tend to show up more with a hot engine under load. Run the engine after dark and look for a spark jumping somewhere ( it's happened to me! ). Clean all ignition related wires/connections.
 

bonzoscott

Senior Chief Petty Officer
Joined
Jul 26, 2008
Messages
745
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

Would it really run fine, and then all of the sudden run like crap? Tough to diagnose the fuel issue with the Carb as it runs fine here, so I'm sure it's getting fuel. I would really like to try and figure out before I take it back out, I don't want to get stuck again. I'll start with the filters.
If there is debris in the fuel system and then the motor demands more fuel under load, it starts restricting fuel - slowing the motor eventually to a stop. Once you've stopped, the restriction in the fuel system relieves itself and the motor fires back up.
This may not be your problem and Another Retired Guy's response would be my second target.
Having a boat with unknown history or sat for years is a good candidate for fuel system service so that you know where you stand.
 

Bondo

Moderator
Staff member
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Apr 17, 2002
Messages
70,465
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

If there is debris in the fuel system and then the motor demands more fuel under load, it starts restricting fuel - slowing the motor eventually to a stop. Once you've stopped, the restriction in the fuel system relieves itself and the motor fires back up.
This may not be your problem and Another Retired Guy's response would be my second target.
Having a boat with unknown history or sat for years is a good candidate for fuel system service so that you know where you stand.

Ayuh,.... Considerin' Viper said there was a metallic pingin' sound, I think it's goin' Lean, 'n detonatin' itself to death,...
 

viper1216

Chief Petty Officer
Joined
Jul 31, 2013
Messages
420
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

**Update**....found a few things today that I believe are causing the issue. The screen filter in the carb was full of crap and the bowl had tons of junk in it. Also found that the head gasket was blown between cylinders 2&3. Got the head off and will be sending off to the machine shop to be planed and a new gasket. Gonna clean and rebuild the carb as well as new filters.

Checked the fuel coming out of the tank and it was clean as can be and no water.
 

bonzoscott

Senior Chief Petty Officer
Joined
Jul 26, 2008
Messages
745
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

Also found that the head gasket was blown between cylinders 2&3. Got the head off and will be sending off to the machine shop to be planed and a new gasket. Gonna clean and rebuild the carb as well as new filters.
Wow! Didn't see that coming! But there's probably more crap in your tank. May want to consider flushing it.
 

viper1216

Chief Petty Officer
Joined
Jul 31, 2013
Messages
420
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

Yep, tank is next. I'm sure there's more stuff in the tank. Figured I'd get the engine done first. Aside from just draining the tank and wiping down, is there a way to actually flush it? Is there some kit or something for that?
 

bonzoscott

Senior Chief Petty Officer
Joined
Jul 26, 2008
Messages
745
Re: Engine died Mercruiser 3.0 after about 20 minutes of running

Not aware of any kit. People have different methods I suppose. My method is to access the tank at the fill tube hole if you can. If not, the anti-siphon valve. Get a good length of tubing (i.e. 12 ft of 3/4 garden hose) or similar. With boat hooked up to truck, start siphoning remaining fuel out. Move the boat 8 inches or so back and forth to slosh the fuel around. And this is where my method will probably get thumbs down!
I fill the tank completely with water and repeat siphon (twice). At the very end, hold the hose end as close to bottom of tank somewhat vertical to try and suck as much water out as you can. Add fuel and a bottle of dry gas, rock boat again.

This is probably over kill and most people just change filters several time. But I did this to a boat with a 50 gallon SS tank that set for unknown time with no gas cap and it worked out.
You may also do this method with about 5 gallons of gas, but filter the fuel each time.
What ever you do, don't try a Shop Vac.
 
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