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Mercruiser 57 no power

M

money_pit

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"Hi everyone I have a 1990 Bay

"Hi everyone I have a 1990 Bayliner with a 5.7 bought the boat with a bad engine.Replaced engine with a recondition 5.7.The engine has no power at all.I have replaced spark plugs,wires,cap it has a new pickup in distributer and rotor button.It has a rebuilt carb and a new fuel pump.I put a new set of manifolds on it and it still has no power.I checked the timeing and it is dead on 8 deg btdc.I installed a new thermastat because it seemed to be running hotter than it should.So this is my problem.It will start and idle and run fine on the trailer.When i put it on the water it will run to about 1000 rpm when you go to w/o/t it has no power starts to miss and run real bad.When you back off on the throttle it will run badly and die.Then it is real hard to restart.I would be greatfull to anyone and everyone for there advice.Thank You!!!!!!"
 
"Hi Ken, it sounds like your e

"Hi Ken, it sounds like your exhaust may be plugged. Try putting a vac gauge on the engine to manifold vacuum and start the engine. If the vac goes down as the engine continues to run (at idle) the exhaust is plugged. If the previous motor was overheated, the exhaust baffles may have melted or could be something else in the exhaust."
 
Thanks Glenn i will check the

Thanks Glenn i will check the vac tomarrow and let you know what happens.I should also say when it starts missing it starts popping through the carb.not real bad but you can hear it.Could it be that the valves were adjusted to tight?
 
[b]" should also say when

" should also say when it starts missing it starts popping through the carb."

That's Fuel Starvation......
 
Check the carb inlet strainer

Check the carb inlet strainer and see if it was put in backwards. Electric choke working? Where did the carb come from?
 
"Hi Guy,the strainer is the ri

"Hi Guy,the strainer is the right way.This does not have electric choke it has the spring in the manifold.I have checked it while running on the lake and it is working ok.The carb came from a rebuilder in Florida that rebuilds Marine carbs."
 
"Kenneth:

"no power s

"Kenneth:

"no power starts to miss and run real bad.When you back off on the throttle it will run badly and die. Then it is real hard to restart".

Bondo said "That's Fuel Starvation......"

Glenn said "it sounds like your exhaust may be plugged"

By your comments it appears you have covered all of the fuel issues except for the vent line and anti-siphon valve. What vacuum reading did you get?

Check the vent line for swelling and soft areas which would reduce the ventilation especially if there is internal swelling of the hose or if the vent screen is blocked. Also look for a section of the vent hose that is lower than the fuel tank inlet; fuel could backup into the hose and stop ventilation which would prevent fuel flow.

The anti-siphon valve may be partially plugged with varnish or gunk. Clean it with carb cleaner and/or replace it.

Either of those conditions would starve the carb of fuel and cause the hard restart issue.

Finally, check each of the flappers above the "Y" pipe as Glenn said. The engine can't breathe if the exhaust is plugged. Flappers can drop into the "Y" pipe and jam the exhaust flow."
 
I havent had time to do the va

I havent had time to do the vac check due to family problems and overtime at work but i will get it done this week and let you know how it goes.The flappers in the exhaust are ok.I have 2 exhaust pipes that come through the hull.The flappers are in the pips near the outlet?If so thay are ok.Checked the vent line and it is clear hose is good.The anti-siphon valve was removed and screen in tank cleaned.Thanks for all your help.
 
Kenneth:

So far you are ahe

Kenneth:

So far you are ahead of the game. Is the carb a 2 or 4 barrell? When you give it full throttle is there a slight lag in response or is it immediate? If there is a lag it could be a defective accellerator pump. If it is a 4 barrel carb are the secondaries opening up?
 
This is a 4 barrell carb.There

This is a 4 barrell carb.There is a immediate power loss.Checked accellerator pump while under way and when engine dies and there is a good stream of gas while working the linkage.I had my wife drive the boat when i checked it.Thanks again for your help.

Ken.
 
time for a compression test; d

time for a compression test; dry first then wet
(tablespoon of engine oil in cylinder) and compare readings. Balanced compression on dry test is good; increase in compression on wet test means rings are bad.
 
"I am having similar issues an

"I am having similar issues and have a question about one of your tests.

I have never done vacuum testing.
I have 1982 wellcraft 23 foot with a 228 mercruiser (new engine 2 years ago).

How do I do the test you descibed:

"Hi Ken, it sounds like your exhaust may be plugged. Try putting a vac gauge on the engine to manifold vacuum and start the engine. If the vac goes down as the engine continues to run (at idle) the exhaust is plugged. If the previous motor was overheated, the exhaust baffles may have melted or could be something else in the exhaust."

Thanks
Gary"
 
"Hellow everyone,Well i just r

"Hellow everyone,Well i just removed the spark plugs from this 5.7 and thay are black.Also i have water in the #5 cylender.Going to run compression test tomarrow (dry and wet)will let you know how it turns out."
 
"Riser cracked inside, gasket

"Riser cracked inside, gasket shot, same for exhaust man., head gasket shot."
 
"Hellow everyone,Well found so

"Hellow everyone,Well found some of my problems.No compression on cylenders#3-4-5 would not even move gauge.Found water in #7 cylender and comming out exhaust port.Also the compression in that cylender is leaking around the valve when you crank it over.This is a rebuilt engine and has about 1 maybe 2 hours at the most on it.Put new manifolds on when i installed engine and new gaskets on risers.Can the risers be tested?I am wondering where the water came from?I will be takeing the heads off tomarrow thay are probably cracked will let you know.Thanks for every ones help and i am hopping for the best."
 
"I don't think this is you

"I don't think this is your power loss problem but I think that engine timing is supposed to be 10oBTDC, mine is."
 
Thanks Rob.Well i removed the

Thanks Rob.Well i removed the heads and both gaskets were blown and water in crankcase.I checked heads and thay look ok.Put new head gaskets on and will run compression test in the next few days.Thanks for everyones help and will let you know how it comes out.
 
Kenneth:

Good to hear you f

Kenneth:

Good to hear you found out your problem. Just curious; "Replaced engine with a recondition 5.7...both gaskets were blown" were the blown gaskets marine type or do they appear to be automotive type?
 
Hi Guy.Well the gaskets looked

Hi Guy.Well the gaskets looked like marine but dont really know for shure.Im going to run compression test tomarrow before i reinstalle engine.Thanks for your help Ken.
 
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