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1975 Mercruiser 140 dies in water but runs with muffs on ?

E

Edin Kordic

New member
Hello,

I am new to the forum and also new to boating so i would like to apologize in advance if i am not explaining my self correctly or if i am not using proper terms for some items.

I have purchased my first boat, it is a 1975 Tri Sonic with a Mercruiser 140.

I got it knowing it needed work, water pump and impeller, head gasket etc.

I got the water pump replaced, then i got the head gasket replaced, it does not overheat any longer and engine sounds good.

The guy that replaced the head gasket and the water pump advised me that i will need a new water shutter but i can do fine without it, i did however order one and it should be here by next week.

I went to a small lake and the boat was running good, went there again and it would have troubles running when in neutral so i would have to shift fast from neutral to drive while idle was high.

The last time i went was today and i ran it at home prior going to the lake and it ran great, i was playing around with the screws on the carburetor and i taught i had fixed it (stupid me)

As soon as i went into water i realized something is very wrong, it would have a really hard time starting, no idle, as soon as i would try to take off it would just kinda bog down and shut off.

One question that i do have is this: there is what looks like a water relieve valve that is on the lower part of the exhaust manifold, when i was on the lake the first time i looked at it and water was coming from it, i didn't think that was supposed to be leaking so i screwed it shut. Could this be why it is having these problems ? Is this something that is supposed to let excess water out ?

Thanks to all in advance for any suggestions !
 
That valve is used to drain the manifold for the winter.-----------------Should be closed and not leaking during operation of the boat.
 
Rebuild the carb. And clean all the filters.

There is one in the fitting that enters the carb, maybe one in the fuel pump, maybe the fuel pickup tube has a screen on it.

Make sure you get the correct carb kit with the correct accelerator pump.
 
read up on how the shift interrupt and lower shift cable interact, sounds like your interrupt switch may be hanging.
Compression test the engine.
 
It's a Mercarb if it only has 1 idle mix screw...it requires a specific thick base gasket. I always use a Merc. OEM kit. The base gasket comes from a dealer. I have 1 you can have if needed. Send me a PM.
 
Well i guess i will start with the compression test and then move to filters and carb if compression turns out good.

Another thing that i completely forgot to mention is that my second time on the lake i went into some pretty low water and i almost got stuck it was kinda muddy sand on the bottom, i got out but im sure some of that muddy water got sucked in, could that have caused any issues ?
 
hystat said:
read up on how the shift interrupt and lower shift cable interact, sounds like your interrupt switch may be hanging.
Compression test the engine.
Click to expand...


You were correct about the compression test, turns out that it had a missfire on one of the cylinders so it was only running on 3.

I hired a mobile boat mechanic he ran a compression test and 3 were at like 120 and one was barley at 30. He took the valve cover off and one push rod was pretty much all the way at the bottom and not pushing against the valve. He determined that in the end it was a bad lifter.

He replaced the lifter by removing this side shield on the side of the block, he charged me only $200 for all of that so i don't think it was that bad.

But here is the problem now, he said he would adjust the throttle for me since i kinda screwed it up, we took it out to the water and he now says i need carb work, possibly fuel lines cleaned, fuel filters etc.

Boat's engine sounds great, has plenty more power but still when we got it on water and he takes off full speed, it runs strong and then it kinda acts like it's low on gas and comes to a slow stop and shuts off.

He was giving me a vibe like he wanted more money but needed a reason to charge me for it so it almost feels like he did not adjust the carb properly and now he is trying to put the blame on the gas tank, filters, carb and so on.....

Is this a possibility ?

Engine sounds perfect, has good compression and idle, it was a low on gas so i am also thinking when he hit a turn on high speed it may have run it out of gas or something....

I may be wrong, but i may be right.

It took him about 20 minutes to figure out the lifter issue and another 30 minutes to replace it, he got $200 i did not mind, I'm not cheap but don't want to pay for something that is not necessary.
 
He's looking in the right area...he didn't overcharge for the lifter work, you got a deal for a mobile mechanic.
 
He would be charging for his total time ( driving time / fuel etc ) not just the time spent on your motor.----$200.00 was a good deal.
 
racerone said:
He would be charging for his total time ( driving time / fuel etc ) not just the time spent on your motor.----$200.00 was a good deal.
Click to expand...

Oh, i was completely ok with $200, i'm just having doubts about everything else he is pushing me to do, boat didn't seem to have any fuel delivery issues prior to this. But i guess ill have to give it a shot and spend some more.

I would also like to thank all of you that have replied.
 
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