flaked rust

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  #1  
Old 09-18-09, 11:43 PM
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flaked rust

I have an 88 Capri 1750 Bayliner with a 2.3L OMC Ford Cobra sterndrive. In the summer of 2006 With the motor nearly wide open (about 5000 RPM) after about 20 minutes it sounded like the engine lost a cylinder, like on a jake brake, it slowed down for a few minutes and then started up to speed again. Then it repeated this again, so I slowed it down, and it only did it on the higher speeds. I winterized it, and shrink wrapped it. I didn't open it up till this August 09, and when I removed the sterndrive I saw a several large flakes the size of a quarter in the exhaust bellows. When I layed down the stern drive I found large flakes of rust at the inside base area where the shift rod goes down into the lower unit by the anode. About a cup full...Just tipping this over a bunch more fell out. Wondering where this came from, I thought this could only come from the exhaust manifold. I removed it and sure enough it was flaked everywhere including the riser and check valve. After cleaning up the riser and exhaust manifold I poured water in the cooling journals to see if it leaked into the exhaust journals of the manifold. Nothing. The thermostat is rusted up but cleanable. I'm wondering about the engine water journals...Is there a way to check them for debris before I reassemble this and close it up for the winter? I'm thinking this may have been why It fouled up on me in 2006...Like a potato in the tailpipe???
 
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  #2  
Old 09-20-09, 07:01 PM
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Location: Montgomery MN
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I'm not sure if I understand completly but will just throw some stuf out there.

was the boat ran in saltwater? If not I don't think there would be any large pieces of rust that would clog anything. Also ifthe water passeges were plugged it would overheat quick, but shouldn't cause the problem you desribed.

I haven't worked on too many boats that were used in saltwater so I'm just thinking out loud. Is it possible that the block rusted throug a cooling passage into a cyl?

Have you taken a compression test?
Is or was the oil milky?
 
  #3  
Old 09-21-09, 01:55 PM
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I'm with you, samauri: Salt water.

hvac, you're in Massachusettes, right? Chances are that boat has been used in salt water at some point.

You can attribute some small bits of rust to the dissolving thermostat. The quantity you've found so far indicates that a large chunk of iron is rusting. Large chunks of iron are normally found only in the block and the exhaust manifolds. They exit through the drive, so it's only natural for you to find them at both the exhaust ports and the through-prop exhaust.

I can't see how anything on the intake side can corrode and produce that kind of rust, so you can figure at this point that the water jacket isn't clogged.

It's easier to pull a manifold.

RE Bogging at5,000 RPM:
Please check your owners manual. I believe you may find the max RPM for that engine is 4600, with a wide-open-throttle (WOT) range of 4200 to 4600. You may have a prop that's not matched to the boat.

Does that boat have a standard ignition (distributor, cap, points, condenser)? A little too much lubricant inside the cap can cause it to bog down.
 
  #4  
Old 09-21-09, 08:17 PM
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rust and bogging down

I run it in salt water...but always run the muffs for about 1/2hr with my well water...after sitting 2 years I pulled off the stern drive and saw white powder around the shift linkage on the right side hinge area. I think the seal/gasket must have leaked, this must have been salt...It looked like the white powder you see around a corroded battery terminal. I scraped it out blew out with nitrogen and sprayed W/WD40 It moves fine. I pulled out the plugs after about 5 years and they were corroded in a bit...BUT I coated the threads W/ Never-Seize and they came out without a problem..except I barely touched the 3rd plug and the ceramic broke off, fortunately the 5/8 socket came out easily. This heavey corrosion I saw in the manifold was absent when I pulled out the engine water pump None of the bad corrosion was seen in the cooling journals or the gooseneck or thermostat housing. The idea of too much lube on the point cam may well be so, due to my own fault. When I was a kid, points came with the lube. I bought a few ounces of this special lube/clearish opague distributor GM grease several years ago while in Alaska. I usually just apply a thin film with a Q tip on the cam lobes. Its about time to change the points, plugs and condenser I quess although I only have less than 15 hours on them...I have the original timing belt on it...it looks like new...no checks, cracks or missing teeth, the tentioner looked lightly rusted a bit but it moves fine and feels solid. I sanded and painted the right side of the engine up (due to rust) and looks like new. I have to reassemble it now...Question...Is this engine water pump a standard ford Tempo water pump??? As to the RPM I stated earlier...I have the right RPM and the OEM Prop... I rarely open it fully, and then only for less than a minute or so.
 
  #5  
Old 09-21-09, 08:31 PM
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I have never tried a auto pump on a marine motor.
 
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