Difficult Cranking and Water in Oil

MikeH

New Member
Apr 25, 2011
27
Chesapeake Bay
Boat Info
1989 200 CC
Engines
4.3l Mercruiser w/Alpha One Outdrive
Hey Everyone,

I am having a new, not so exciting issue as we are on the verge of beginning summer. I will start with a little background:

I have a 1989 4.3l Mercruiser with an Alpha One Gen One in a 1989 Sea Ray 200CC.

I replaced exhaust elbows and exhaust manifolds about a month ago. I also changed from the old flappers to the updated center hinged flappers in the Y-pipe. I have put about 15+ hours on everything this spring with no issues.

This Monday, I checked the oil and it looked good, correct amount and proper color. I went out for a few hours on Monday evening, and a couple of hours on Tuesday evening, no issues either time no rough running or idle issues or noises.

Thursday evening I went to start the boat and it just clanged (not a nice sound), so I let off the key quickly and decided to see if I could hand turn the motor and check the oil. Oil quantity seemed good, but seemed as though it may have been darker than earlier in the week (could be imagination). The motor turned but with more resistance than it has in the past. As I sat there thinking of my options, I realized I hadn't changed the fuel/water separator in a while, so I thought it is easy and I had one at the house, so I put a new one on, and hand cranked the motor some more. The hand cranking got more fluid to the point where I felt okay trying the key. It fired up and ran pretty well at about 1500rpm, so I let it go for about a couple of minutes, but when I dropped back to idle it was rough with a lot of vibration, so I cut it off.

I went back and checked the oil and there was now some clouding showing evidence of water. I called it a night and went down this morning and there is definitely evidence of water and the overall volume of fluid in the pan is now above the full mark.

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The only other observations when I was running it was that there appeared to be a slight sign of dark gray smoke (very minimal, and this seemed to stop as I ran it), no sign of white smoke, or blue gray smoke. Also, very strange, the thermostat did not increase at all as it normally would, but when I shut it down it popped up to 145, then went back zero. This gauge normally holds the motor temp with the key in the accessory position and it normally increases gradually over the first few minutes of operation until it hits about 145 and backs slightly down when the thermostat engages (may be a total coincidence but just seemed strange).

So, a couple of questions:

If a fuel/water separator reaches capacity, is it possible for water to go into the cylinders?

What is the best place to start with the diagnosis?

And any other thoughts or suggestions would be greatly appreciated

Sorry for the long post!

Thanks,

Mike
 
Take the spark plugs out and inspect them for the presence of water.

While they’re out, crank the engine to see if water comes out of any of the spark plug holes.

Pressure test the raw water system as previously mentioned followed by a compression test.
 
Great, thank you for the responses! I plan on doing these tests this weekend and then report back what I find.

Thanks!
 
Once you figure out and fix the water source be prepared to change the oil And filter several times until it stays clean.
 
First step is drain the oil soon and put some fresh in! Pull plugs and put marvel mystery oil in the hole and crank it to coat the cylinders. Now here is what I have found. Had two engs of my own and my buddy and 2 do the same thing. The heads will crack around the back cylinders. I didn't know what the issue was on mine so I replaced the long blocks. Wish I hadn't. On my buddys boat I walked him through preserving the engine and we changed the heads and both were perfectly fine and ran awesome. How I found out was another guy had the same issue changed the heads and kept running it hard for many hundreds more hours. You can save the engine and fix it fairly cheap.
 
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