Outboard Overheating

[JONBOAT66]

Hello Everyone, First Time On Forum. I Have A 1985 Mercury 150 Xr-2
Recently Rebuilt The Motor After Blowing Up A Piston, Complete Disassembled And Horned All Cyliners And Replaced Both #1 And #2 Pistons For Damage, Reassembled Engine, Reset All Adjustments, Started And Ran In Driveway All Ok, Took To The Lake And Ran It And Now It Overheats Badly Especially At Higher Rpms, Stop To Idle And Engine Dies And Hard To Restart, Suspect Combustion In Cooling System And Water In Cylinders, Did Not Run Compression Test Again When Hot, Removed Cylinder Heads To Inspect, All Look Ok, Has Anyone Heard Of Cracking Issues Or Stretching Of Bolts

 

[Windykid]

Re: Outboard Overheating

Welcome to I-boats! I didnt see any mention of tell tale or that you changed impellar or thermostats.

 

[rndn]

Re: Outboard Overheating

What was the cause of the first blow up? Is it getting oil? Is it getting water as stated above? Is water coming out of the tell tale?

 

[JONBOAT66]

Re: Outboard Overheating

Yes, I Changed Water Pump And Housing And Both Thermostat, Pretty Much A Overhaul Of The Engine, The Tell Tale Is Spitting Out Water, After Running The Boat At Top Speed And Then To Idle The Motor Sounded As If Were Steaming

 

[JONBOAT66]

Re: Outboard Overheating

I Don't Know The Reason Of The First Blow Up, Yes It Is Getting Oil, Someone I Was Talking To Stated That It Was A Common Thing For
Mercury Outboards To Run Lean On The Top Piston And That They Had A Bulletin Pertaining To Changing Out The Jets In The Top Carb. He Said I Could Probably Find It On The Internet But I Haven't Been Able To Find It, Does Anyone Know Of Such Bulletin,

 

[j_martin]

Re: Outboard Overheating

I don't have a service bulletin, but I know that on some merc v6's the carbs that feed #2 and #5 have .002 oversize mains, and usually .002 smaller idle jets. Which actual carb depends on if it's a vertical or horizontal reed front.

Read the plugs and give it what it wants.

There can be a hair line crack in the exhaust divider that sprays a little water into one or more cylinders through the exhaust port. If a cylinder is too clean, I'd be worried about water in it.

hope it helps
John