Source
r/boating•
cs556

Diagnostic Help

Today on the lake our motor overheated. It’s a mercruiser I/O 135 hp on a 1988 sea ray. There were no signs until we noticed some smoke/steam and a check of the temp gauge showed about 200. The engine was running just fine the whole time. The engine is supposed to run at 140. I watch the temp gauge regularly and it had been normal last time I checked, very recently. When we noticed I immediately powered down and cut the engine. It did diesel for a few seconds which I know can’t be good.

Fortunately we found a launch downwind and used the trolling motor to get us in.

Anyway, shits fucked. Water in at least two of four cylinders. It was totally hydrolocked. Had to remove the plugs and turn it with the starter. Water shot across the garage.

My plan is to pull the head tomorrow to assess the head gasket and dump the oil to look for water as well as take the lower unit apart and inspect the impeller. I’ll be replacing it since I’m sure as shit not going through the trouble of getting that fucker apart without doing so. From my understand and in order of severity, it’s either a busted head gasket, warped/cracked head, or a cracked block.

My question is how to differentiate between these issues. Unless it’s a cracked block I, should be able to get it back up and running. If it is, I don’t want to repair the head gasket only to find out the whole thing is fucked.

Any pointers would be greatly appreciated.

EDIT: After checking the compression and finding all cylinders to be good, I turned it some more with the plugs out to get the last of the water out. After that I replaced the spark plugs and it started up and ran fine on muffs. The water coming out of the engine looked a little weak so I'm still going to replace the impeller. Thanks for the tips!

Posted Jul 22, 2018, 3:43 AM UTC · edited

38
adam_smash•

You can get the head blue printed and magna fluxed to check for warping and cracking. Shouldn't set you back too much. If it's a head gasket issue and it caused that much water to get in the cylinders, it will be obvious when you pull the head. A cracked block may not be visible but can be magna fluxed (fancy term for magnetic dye test).

5
cs556OP•

Can most shops do this service? The boat is in the Madison, WI area.

1
Chrisfindlay•

Most machine shops that perform engine work will do this but it does mean pulling the engine. What engine do you have is it a 3.0l 4 cyl. a "470" 3.7l 4cyl. 250 cubic inch straight six

3
cs556OP•

It’s a 3.0 in-line 4

1
justphiltoday•

Before you go crazy ripping things apart, coming off plane while the engine is dieseling will suck water back through the exhaust and hydraulicly lock the engine. First thing to do is rig a block pressure tester and pressure test the block. I made mine with a small pressure gauge that reads 0- 30 lbs, a male air hose fitting, ball valve, series of 1/4 galvanized pipe pieces, male hose nipple, chunk of 3/8 hose, with a 1/4 pipe hose nipple on the end of the hose that threads into the block drain. Plug the water inlet and outlet to the engine, then screw the tester into the block drain. Apply 20 lbs of shop air and see if the pressure drops. If it stays pressurized, you're golden. Purge the water, change the oil and filter, and install a complete sea water pump kit and let her eat. If the pressure drops, looking ànd listening with the spark plugs out will give you indication where your problem is.
Edit- here's a pic of my tester: https://imgur.com/gallery/ALLk9Xv

5
thewolfpope•

Do a compression test first. If you have low compression then pull the head. Check for tuliped valves and any visual cracks. Take the head to a machine shop to have it magna fluxed if you couldn’t see any cracks and have a valve job done if any were tuliped. Replace the head gasket and your impeller and get going!!

1
cs556OP•

Thanks for the tip. I’m going to do a compression test today.

2
bubbleTime1:snoo_surprised:•

soak piston/rings in marvel mystery oil for starters

1