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My service manual says to change my cylinder head o-rings every 300 hrs. it now has 735 hrs without issues, do people actually do this? It seems a little excessive - 1998 Mercury Offshore 225 hp. carbed
You'll probably get as many opinions about this as there people reading your post. I'll start by giving you mine. I had an old 115 Johnson and the popular advice at the time was new head gaskets every 100 hours. I did it for the first 200 or so (don't remember now, too long ago) and then thought I was wasting money. The engine ran great. Then on one trip, a head gasket gave out and water entered a cylinder and the engine was toast. The issue with head gaskets is they may last for an engine's lifetime, but if one fails, you usually (usually!) don't get a second chance to make it right. I would also check into Merc's policy (or the conventional wisdom) of having the lower crankshaft water seal changed cause if it fails water enters the block and the engine's done. As I recall, this was a part of regular maintenance on the first generation 200 Black Max. This is just my opinion, because I'm no expert and I don't really know for sure about your engine.
No expert either, but I had an 83 or 84 Evinrude 200 (carbed, of course) for 19 years. The only maintenance other than fluids/plugs and normal stuff was for a failed temp sensor sender--false alarms. Factory head gaskets. I might still have it except I couldn't put it on Tahoe and needed more room for grandkids. The boat was a Wellcraft Sunhatch cuddy. I thought it was the best cuddy design ever in that there was a sliding hatch that opened about 2 1/2 feet toward the bow. Easy to get to the bow and a place for someone to stand. But it didn't last long
You do not want to do that. Merc tech advisers put that in the manual to cover their ass at the time for an issue they had with them. They updated the gaskets and it was all done. If you don't have an issue don't mess with it however if it needs it do it. Make sure you get the mercury OEM part because a lot of the aftermarket parts will be the old type gasket.
Dont do it unless you need it.
__________________
"Im only comfortable with a three man brain trust." -The Janitor
Your post, MattMutt, points up my dilemma. You said don't mess with it, but if it needs it do it. Sometime the way you find out "it needs it" is when water gets in and detonates a piston. I don't know the answer. It is rather to hard to spend the cash to make repairs on an engine that is currently running great.
That's called "preventive maintenance", not repairs.
You change the coolant and oil in your cars even when they are running great, right?
Sure I do. And I compare that to changing fuel filters, l/u oil, water pump and sparkplugs on my outboard. However, I don't as a part of general P/M on my truck, change the head gaskets, oil pump, water pump, radiator. See my point. At some dollar level, it's no longer P/M in my mind. And that's what cost me my engine. I was too cheap to pay to have the head gaskets changed.
I don't as a part of general P/M on my truck, change the head gaskets.
If you had a new Ford Powerstroke you might
The head gaskets on this outboard are almost as easy to change as the spark plugs. All you need is some simple hand tools and a torque wrench. I have a Merc shop manual for the 135-200hp Merc EFI and Carbed engines. The torque soecs are probably the same but you should check. Someone here probably has a manual and will copy the page for you if you dont.
'Meanor, I don't have a Merc. I knew a guy years ago with the Black Max. Do you have anything in writing, or do you remember anything about that lower crankcase seal? The mechanic who put a new powerhead on his engine said that while the seal issue was not address in any of Merc's service literature, it was an unwritten rule among mechanics that it should be changed on a routine basis. Anybody ever hear of this? And this was way back probably in the '70's???
'Meanor, I don't have a Merc. I knew a guy years ago with the Black Max. Do you have anything in writing, or do you remember anything about that lower crankcase seal? The mechanic who put a new powerhead on his engine said that while the seal issue was not address in any of Merc's service literature, it was an unwritten rule among mechanics that it should be changed on a routine basis. Anybody ever hear of this? And this was way back probably in the '70's???
The head gaskets on this outboard are almost as easy to change as the spark plugs. All you need is some simple hand tools and a torque wrench. I have a Merc shop manual for the 135-200hp Merc EFI and Carbed engines. The torque soecs are probably the same but you should check. Someone here probably has a manual and will copy the page for you if you dont.
quote=Mr. Demeanor;2622559]If you had a new Ford Powerstroke you might
The head gaskets on this outboard are almost as easy to change as the spark plugs. All you need is some simple hand tools and a torque wrench. I have a Merc shop manual for the 135-200hp Merc EFI and Carbed engines. The torque soecs are probably the same but you should check. Someone here probably has a manual and will copy the page for you if you dont.[/quote]
Thanks, I have the manual and even the gaskets, just was too lazy to put them on, but after reading the replies here, I will make the time-
Mr Demeanor -
Have you been catching any Gags in close up there? We have been limiting on some really nice red grouper, up to 31" but not one gag yet-
The Gags are just starting to show up in shallower depth (less than 70'). Guys are starting to troll for them in 50' with decent results. I caught a 26" a few weeks ago snapper fishing at night in 55'. The surface temp is about 72 now.
A 31" Red Grouper is a freight train....nothing to complain about for sure. If it wasnt for the worms, I would take them over gags due to the thick filets. Where are you located?
Changing cyl. head gaskets, 300 hr. maint. ?
I would ask on 
