Rust pieces exiting the exhaust..

pstew96

pstew96

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I ran my engine on the driveway Merc 383 stroker, and a bunch of rust particles came out the exhaust most smaller than a dime, is this normal for an engine about 2 seasons old? Also, could it have caused my thermostat to stick as the temps went from 170 t0 220 then back and forth.??
 
I assume this is a raw water engine up and down temp can easily be caused by the low and uneven water flow from the hose. Rust particles can come from the block or manifolds drying and rusting. Did you flush it at layup?
 
Yes, flushed it, ran it to winterize it and the engine was installed including new risers two seasons ago. I am in a brackish area of Babylon and the barnacles are minimal, so I don't think I should be rotting so quickly. During the season I take her out two or three times a week, so it doesn't really sit.
 
well there is no guarantee but I seem to recall crap coming out of exhaust on first start up as well si I would probably just run it and see what happens. If you are concerned a compression check is always a help for sleeping well.
 
More than likely it's coming from any raw water side of your exhaust system. I hope it's not a raw water cooling system. it'd be a shame on a 383.
 
I've had exhaust manifold failures where the rust created flakes that looked like Fritos.
 
Perhaps just mostly scale flaking off old exhaust exhaust hoses during slight flex and heat expansion of 1st seasonal startup?

What rpm was the engine run at on the muffs? Anyone else in the house use the water supply?

Since you only mentioned new risers, it is full FWC , right?
But if RWC , does the cooling system employ "poppet valve" style t-stat bypass valves at the t-stat housing?
 
Its raw water cooled with "poppet valve" style t-stat bypass valves at the t-stat housing....
 
Let me guess, the engine has been sitting since you winterized it and you drained the engine/cooling system when you winterized it. Had you replaced the water with antifreeze, it would have come out nice and clear when you first started up.
A buddy of mine used to keep his boat heated during the winter and not winterize the engine. The first start up of the spring, the water looked like mud coming out of the exhaust from all the rust. My boat was winterized with AF and the first start up, my water/AF was just as clear and clean as the day I put it in.
 
There is an old mechanics trick occasionally employed when an inboard engine showed signs of overheating on the 1st floating sea-trial run of the season. Let cool a bit , restart setting throttle ~~1000 rpm, and fully close the seacock for just a few seconds to build extra RW suction. Then reopen and the strong rush of RW would tend to knock loose and flush a lot of rusty gomph from winter storage. Don't wait too long and burn up the impeller. And it's always possible debris knocked loose could lodge somewhere else not desired.

I've 1st seen this work with a FWC inboard I was on at sea long ago and temps went down from alarming 212+* to consistent normal ~~168 . It was impressive. The immediate exhaust/wake looked very brown with debris but cleared quickly.

Now I usually try that procedure with my non-overheating FWC I/B's 1x or 2x a season to potentially "help things along". Hasn't hurt anything yet, and sometimes riser/elbow temps drop to more comfy feel to my palm if they had felt slightly elevated.

As always, ..."Your mileage may vary."
 
Patrick- It's possible fluctuations in house water pressure varied the pressure on those spring loaded poppet valves , in turn varying bypass and engine temps. Or they &/or the t-stat were affected by debris, or supply or flow was restricted elsewhere. That certainly narrows down the temp issue source. :D
 
Sandy that is interesting because I don't think impellers create much suction.
 
Bruce - I believe they do when the RW pump is running at relatively low rpm and the impeller is still wiping the wear surface and especially if flow supply is restricted. That's why the supply side hoses are generally wire reinforced to prevent suction collapse.

There certainly is quite a nice burst of RW water out the exhaust when I reopen the seacock after a few seconds.

CYA :D: I'm not recommending this procedure to anyone , just noting I have seen it provide very beneficial results when we could not have proceeded without it.
 
So, it doesn't seem to have had any adverse affect, the boat is running very well. Temps are fine also.
 
great thanks for the follow up. My experience parallels yours
 
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