FOREVER YOUNG

I have a 35 ft fountain with pair of 575 sci mercury motors. One of the motors is spitting through the breather and cuts off between 800-1000rpm at take off and slow down. It will immediately restart and it might reoccur several time before it works and you can get on plane. I have replaced the coolant temperature sensor, map sensor, and throttle position sensor. Has anyone else has the problem or have any suggestions?

GO4BROKE

iTrader: (1)

Spitting through the breather? Do you man back firing through the intake? Broken valve spring?

keegan

When is the last time you changed the cap and rotor????
How many hours on the engine?

FOREVER YOUNG

I'll check the valve springs and cap. Motors have about 300hrs

39 Unlimited

Just fixed a 575 with same problem. Check vacum at idle, should have 6 Lb's of vacum. Tried everything mechanic found intake manifold gasket was leaking. Pulled intake installed new gasket problem fixed.

4bus

iTrader: (4)

Good call, if they are factor motors fountain puts boost/vac gauges right on the dash.

I am also curious by what you mean "spitting through the breather" I hope you are not talking about oil blow by, that would require a tear down.

If you are talking about backfiring it could be a number of things, the guys are right on with ignition and vacuum leaks as the first tests. Change those caps and rotors at least every 2 years, I do mine every.

Other things to look for in a 575sci.

Clogged IAC- pull and make sure channel is clean
Fuel filter that is mounted on back of engine, commonly neglected
Weak mechanical fuel pump- pull pump oil drain plug and see if it is full of fuel
Clogged or bad injector- check injector spray with spark arrestor off (air cleaner) use a timing light hooked to #1 and point at spray for clear reading
bad fuel pressure regulator- too much pressure at idle, make sure you have no more than 30. regulator is mounted under engine in cool fuel box (pain)
fouled spark plugs - near impossible to clean out using engine after fouling. change
thermostat stuck open- keeps you in "cold start" for too long and loads engine up, will foul plugs as well. Make sure it is getting up to 150. ECU is programed to add fuel all the way up to 130
Check base timing is set to 8 degrees. The ecu uses timing to control idle speed along with other things.
Frayed injector wires grounding out injector and holding it open- the wires are very close to the mounting point of the spark arrestor, if pinched they can ground injector and flood engine.

Get problem solved, backfiring into a blower is never a good idea.

That should be enough to keep you busy, let me know if you have other questions

Revinchevy

Check all exhaust side valves. Had a similar issue with a 525 sc. It was doing the same thing and found that the exhaust valve on cylinder 3 was barely opening and sending the combustion back into the intake. Lost a lobe on a cam. Two different engines but thought I'd share if it helps.

Quinlan

iTrader: (1)

Get your head gaskets done ASAP too. Will have more issues sooner than later.

JRider

iTrader: (1)

head gaskets are a must at 300hrs. You may be able to cut an oil filter open to see if there is any cam lobe missing.

Tom A.

Very familiar with 575's and their problems.

First, check the Computer. I had one good motor and one bad motor doing the same thing yours did and it turned out to be a bad ECU. changed both to be safe.

Second, definitely have the intakes and gaskets checked they are notorious for corrosion and failure. I replaced my intakes with a custom set made by "The Blower Shop".

Third, at three hundred hours you should definitely pull the heads and do a top end on the motors. At the same time replace the head gaskets and check the bottom end.

I am in the process of rebuilding both of my motors now because of bad fuel but I got 6 full seasons out of my 575's (Ron Potter built up to 700s) by doing the above.