7.4L Overheat and no oil pressure.
 

Bought a used carbed 7.4L to get me on the water as my engine is way overdue from builder.

Engine looked great in video and ran well out of the boat. Was located 2 hours away and had it shipped up to my mechanic.

After receiving the engine, I can see black overspray all over the engine.
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Mechanic had to remove ex manifolds to install in the hull. At this time I see all the rust/rot present. Head bolts are Shot.


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Fuel pump was shot. A lot of fuel came out of the sea water pump lubrication hole. The inspection hose was clogged full of chit.


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So I replaced the fuel pump.

There was a problem with the water circulation pump pulley wobbling/rubbing on the harmonic balancer. So I replaced the water pump. (It already had a new sea water pump installed)

Contacted the seller and got the sorry you're not happy BS.

Pushed forward with the install as it's getting late in the season.

Fired it up and it has a slight miss when running on the hose. Did a complete tune up. Plugs, cap, rotor, wires, dist sensor, and fuel filter.

Still had a miss. Checked timing and it's at 18* BTDC. Suppose to be at 8* (the dist hold down bolt was loose)

Corrected that and turned attention to the carb. (Weber 4 bbl carb) 1 idle mix screw is set at 3 1/2 turns out and the other is around 2 turns.

Corrected that, and have a decent running engine.

For some reason the warning buzzer isn't working with this engine. So I'm going to have to watch gauges closely.

Took her out for maiden voyage. It did well up until the WOT test. Did a short sprint (300 yds) and only got around 3800 RPM with 21P prop.

Engine temp was up around 175* Oil pressure was now around 30 PSI at idle. (down from 40)

Did a hard accel test for another 300 yds and felt a loss in power. Looked at gauges and oil was down to 20 PSI. So I shut it down.

Open the hatch and buddy says smoke is coming out. Look over everything and you can hear the water boiling inside the intake manifold. Smoke is coming out the valve cover breathers. Everything is hot.

Check all hoses and everything is coming back clear. Removed the sea water pump and the impeller is perfect. Remove the thermostat housing and find this.


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Removed the damaged thermostat and fired it back up.

NO oil pressure at all. Wasn't knocking or anything, but nothing registering now. Didn't see any oil spraying on the rocker arm visible through the oil fill in the valve covers.

Shut it down and got towed in.

Ran less than 10 mins.

Anyone think I got a case to get some $$ back from the seller listing it as a "good running engine"?

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two hours away isnt that far so id pay him a visit. bring a couple of your strongest friends. lol

Zero oil pressure and its not knocking or at least ticking???
Hook up a mechanical gauge

Looking at the heads….Salt water motor ? Looks horrible.
Reg steel thermostat ?

If oil psi reads low with mechanical hauge,
, i’d show up to the sellers door with motor.

A used motor looking good or bad some things should be looked at before even firing it up. Thermostat is one of them

That said, its so rusty, use a mechanical gauge as SB suggested. The motor is rusty so senders may not be making good contact on the ground side

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2 hours away? I'd of bought in person.
I get the urge to boat but I wouldn't of ever even installed that.

Show up with some friends and file a complaint with local PD and with whatever site you bought it off of.

Hard to believe, but Mercruiser says 4 psi oil pressure at hot idle is acceptable....

2 hrs away, I was going to pick it up personally. But it ended up costing less to have it shipped to me, than to drive down there and back. So yes, I agree with you all with going in person. My mistake absolutely. Please remember, I am 15k invested into the new engine that is being built for me thus far. This was supposed to be a cheap engine to just get me on the water and not lose this season entirely. Tried to save a few bucks and trusted the positive reviews I found from previous customers. If this was to be my permanent engine, absolutely different scenario.

Hard to figure out the amount of rust just behind the ex manifold, mostly on the even side cylinders. Not nearly as bad on the odd side.As far as salt motor? Central OH is a long way from the ocean. Not saying it couldn't have been shipped, but prob just poorly cared for would be my guess.

Will try the mechanical gauge. Prior to the overheat, the sender was working fine.

As for the lack of noise, the engine was only running for a few seconds after start up. Would have thought it would be knocking, squeaking, screeching, something. But looking at the oil pressure gauge, it never came off the 0, saw no oil splashing on the rocker seen through the oil fill on the valve cover, and I shut it down. There was oil pressure prior and everything was lubricated. Maybe it takes a little bit for it to start to make noise? I don't know.

I was wondering about the thermostat since everything else seemed to be questionable, but since it didn't show any signs of heat problems while running on the muffs, I didn't pay much attention. Looking back on it now, the ONLY thing that was replaced on the engine was a new sea water pump impeller and housing. So now I'm suspecting the engine had heat problems prior and they just threw it on thinking it was a bad impeller. When in reality, it was the thermostat. No excuse for me to not address it, for sure. Just tired of sinking more $$ into this engine that was supposed to be "cheap"

With the fuel pump, water pump, and complete tune up, I dropped an additional $500 on this thing. Should have done another $30 for the thermostat and gasket.

Thanks for the replies guys. Was more of a venting post than anything, but was also wondering what others might do if this was them.

just remember, the most expensive project you have is the cheapest one to buy.