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Merc 470! Problems! Pls help!!!!!

S

Sledhill87

New member
I purchased a 83 Larson with 470 2 months ago, ran fantastic until a week ago!
Was out on water tubing, when boat started to act up, caughed and farted and tarted to
bog down, so I put throttle down to idle, and idled fine. Wouldnt get back up on plane. After a while of idling back to dock it kicked back in and throttles right back up.

The next day, took it out and it did the same thing, so I put on trailor and went home, changed some ground wires, spark plugs, and oil change. Fired it up with no water(mistake). Took it out later to river and went boating. Didn't make it 1 mile and she starte to over heat. I ended up changing water pump and impeller in bottom end! Ran it on hose with muffs, no water was coming out of prop, but out a hole on bottom of out drive where it mounts to boat.

Figured maybe it was suppost to, took out on river again and over heated in 5 mins of WOT. I could here the coolant boiling! Pulled plug on heat exchanger and fire boat up and it was pumping hot water out, so I figure impeller is fine.

So, all in all, can't get boat to plane and over heats in minutes, took thermostat out and no difference!
Any info would be greatly appreciated, I thinking head gasket?
 
What do u mean took place of pump? As in the pump might not work,
and the water makes it look like it works? And I had it in river when I pulled plug on
heat exchanger and water was pumping through the drain.

Let me know thanks!
 
Fired it up with no water(mistake).
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You burned it up by doing that...LU has to come off...replace impeller minimum work...replace upper pump cover if it melted. Might want to check the bottom half of the housing if the top is melted...may have damaged oil seal.
 
Hey does your 470 have an alternator? Looking for brackets for mine. Also in the front cover of the water pump on motor there is another impeller in there. Check that one yet?
 
Sledhill87 said:
Yes I replaced impeller and cover after I fires it with no water. So it hasn't ran outa water sine I replaced it!
Click to expand...

If you replaced the impeller and the top impeller housing let us know EXACTLY how all that went...

Obviously you did something wrong or someone before you did and the incomming water system has to be diagnosed.

Just saying you did is not good enough.....details details details........we cant see your issue from here....


When attaching a hose to the outdrive you are inducing water pressure and it will overcome a lacking water pump impeller.....


What I am thinking is you took it apart, and the copper tube (what did you do with that????) I bet you had it in your hand?

You put it in the water pump impeller housing and then bolted the lower back housing to the upper housing? Correct?

If this is the way you did it, that was wrong. The copper tube must be inserted into the upper plastic housing FIRST!!

I am betting you PINCHED the rubber grommet that the copper tube fits into and now it is pinched and cutting off water to the motor.....Seen it done this way a ton of times........

Report back and let us know what you find.

Once this is cleared up then get back to your original problem..

I will also say that one issue that can occur with these is the radiator cap does not seal well and a small amount of antifreeze will dribble down to the spark plugs (visable as a dried trace) and this will short out the plugs and cause a ignition type running problem. Just some food for thought.

Also the distributor is on an angle this wears out the distributor bushing causing the point gap to change when warm. see how much slop is in the shaft and if it is affecting the point gap...

The 3.7 is a bastard child. NOT A GOOD PRODUCT!!!!!

If the motor runs good you are lucky. If not good luck!!

No direct replacement as it has a front motor mount. Possible only alternative would be a standard inline GM 4 cylinder....Not sure it can be swapped due to motor lenght differnces...

A V6 would be the correct replacement but you would need side motor mounts........
 
As for water pump installation, the copper tube never came out of upper portion of out drive.
i installed the impeller turning the shaft clockwise and pushing housing down onto impeller.
i did notice when I put the lower plastic tube from pump housing to copper tube, it seemed
really loose on the copper tube.

As for distributor, I will look into it, and a compression test if I get home early enough tonight.

How hard would it be to install side motor mounts? I could probably fabricate something or get something
made up!

Thanks
 
The rubber exhaust elbows are located at the back lower left hand side of the motor. Will be two 4-6 inch rubber hoses that are only about 6 Inches long. The exhaust bellow is located on ur outdrive. There should be 2 rippled rubber hoses coming out of ur boat thru ur outdrive. One is a 6 inch. That's ur Trans mission bellow. The other is a 4 inch.just below the other. That's your exhaust bellow. See if it got hard from overheating. Mine did
 
Did you install the fat oring on top of the water pump impeller housing??

It is sometimes called a slinger but what it does is keep EXHAUST gases from entering the water pump housing.

If that is missing the you very well could be getting bubbles in the water stream.

Boats with a V6 or V8 have large stringers molded into the fibergalss on each side of boat floor. The motor mount bases mount to these.....you most likely aint got em......

NO online manual.........send me a Personal message with your email address, a good one that can handle large files!!
 
How hard would it be to install side motor mounts? I could probably fabricate something or get something made up!
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As kghost stated the engine mounts are integrated w/the stringers that run the length of the hull. The mounts are solid blocks of hardwood bolted and then glassed to the stringers making them and the hull the same structural unit which distributes the engine weight over the entire hull. Make sure the tops of the stringers you install are level and commensurate w/the engine that you are planning on installing. Unless you are proficient in this type of work I suggest that you hire a professional to install them.
 
I need alternator brackets for mine and everywhere I've looked they are in the hundreds just for the brackets. I have the alternator. Just need brackets.
 
lowkey83 said:
i need alternator brackets for mine and everywhere i've looked they are in the hundreds just for the brackets. I have the alternator. Just need brackets.
Click to expand...

start your own topic/thread. It is inappropriate to "hijack" another thread for a different issue than the original poster......
Thanks........
 
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