Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Good afternoon all,
I have a 1998 4.3L Merc with Alpha One.
Boat has been in freshwater 95% of it's life with the occasional strole in the waterway. Afterwards flushing out is always a must.
I bought it third hand in 2005 (march) and have not had any major issues and have done most all the maintnence myself.

This past weekend, while riding in the lake at approx 30 mph, we lost power, boat would not go over 20mph and was struggling to do that. Heard 3 backfires and then we stopped the engine. After inspecting Oil, Prop and other obvious things, we didn't find anything. So I fired it back up, it spit and sputter at low end so I gave it throttle (in neutral).
After it got up to about 1500 rpm, it smoothed out and would hold 3-4000 RPM's. I backed it back down and kicked it in gear... under power, boat would not give ANY power... it's like I had lost more than 1 cylinder.

Trying to idle and sputter my way back to shore, after about 5 minutes of this, a loud infamous CLUNK and the motor would not spin.

After back at home int he driveway I decided to pull plugs, Number 2 and number 6 (both on Starboard side of engine) were dripping wet with water. I pulled all the plugs turned it over to get the water out, put the plugs back in and fired it up (Dry) and it ran great abotu 10 - 15 seconds then i shut the engine off.

That's where I am,

After doing research, many people are pointing to either Intake Gasket or Exhaust Risers/Manifolds. As far as I know, these are the original Manifolds on the motor that came with it.
THese manifolds are 1 piece... they do not have a seperate 4 bolt Riser that many other system's ive seen have. Here is a link to what mine looks like:

http://www.**********/parts/search/Merc2/Mercruiser/4.3L%20-%20%282BBL%20Gen%20%2B%20GM%20262CID%20V6%29/0L010044%20THRU%200M614999%20%281998%29/Exhaust%20Manifold%28One%20Piece%29/parts.html



My question is, what shoudl I do next? ANd how much skill level is needed to remove / reinstall intake gasket or exhauxt manifold gasket. I am pretty confident I can do it, just dont know if i'll need special tools or what?
It looks pretty straight forward, just bolt on parts right? Manifolds look god Awful heavy, I will need help with those it seems.

Shoudl I start with Intake and move to Exhaust? Or judging by Age of boat (617 hours) shoudl I plan on replacing all. Most Everywhere i've found on Internet always points back to a two piece Riser/Manifold combo.... Since mine do not look like that and my Manifolds need to be replaced, Can or should I go to a two piece setup, or do I have to find the exact same parts (which seem to be obsolete now)?

Any advice, help would be wonderful, I just dont know which way to go. I can always go talk to my local merc dealer, but I feel as If i'm cheating him out of valuable time picking his brain asking questinos and not brignign the boat to him to work on it.... As i would feel the same probably.

Thanks for your help in advance.
Michael

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Sorry, try this link for picture of exhaust manifold

http://www.perfprotech.com/store/assembly/Exhaust-Manifold(1-Piece),2332-160.aspx

obviously these are very expensive... if i take them off and find they are the cause of the problem, could I just try and clean these out and replace the gasket and start again?

Not sure but just trying to mke a good educated decision.

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Have a read of this service bulletin on water intrusion.

View attachment Water Intrusion 01-13.pdf

You have to be very careful about "Research" you can read a lot of completely wrong information in old threads, by people that really have no clue what they are talking about. You only need a computer to reply to posts, knowing what you are talking about isn't required. I also know for a fact that a lot of people read something about a completely different problem but like the answer given and take it as gospel.

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

eighty2scrambler said:

obviously these are very expensive... if i take them off and find they are the cause of the problem, could I just try and clean these out and replace the gasket and start again?

Click to expand...

Those one piece manifolds have been the demise of many a good engine. Replace them with 2 piece.

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Don,

Wow, that SB is a much better form of "Research" than what I was finding earlier Thanks for that. Plenty of things there to consider about how the water was getting into the Engine and why...

Another question, Is there any way to "test" these manifolds to see if they need replacing or due to time and age of boat, should I go ahead and plan on replacing those? What are things I should be looking for, once they are removed, for a "bad manifold"

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Ok, and another...,

Should i hook the muffs up and run the engine to rule out water entering in through the Carb?
Here's why I ask..

We were camping next to the lake and the boat was in the water... that night a HUGE and i mean HUGE Rainstorm came... 8 - 10 inches in about 6 hours.... (yes we were fine in our tents, thanks for asking)
Lots of wind blew and there was water on the top of the flame arrester....so, some next ot he carb.... i doubt still that, THAT much water came in the carb to hydrolock engine, because A LOT of water came out of the engine when i spun it over with no plugs in it.... But I could be wrong in thinking that much rain can't come in through the carb.

just wondering how lucky i got when it hydrolocked not to damange anything else... i dont want to take another chance, i'm not usually a lucky person

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

So I got brave, hooked water to muffs on leg, fired up the boat and ran it at 1000 RPM for about 15 minutes. It never missed, hiccuped, just ran smooth. However, The Manifold on the starboard side of engine (the side where water came in last weekend) was very very warm, HOT is the correct word. The manifold on the port side of the engine was cool to the touch.

I pulled the plugs, DRY As a bone, looked good... no water in cylinder at all.


Could someone give their advice on where they think the water was coming in, based on the info i've given?
I still think it came in from the starboard manifold possibly breaking down on the insdie. Is there a TEST I could run to test these manifolds out to see if they are bad?

Any input is appreciated.
Thanks,
Michael

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Is there a TEST I could run to test these manifolds out to see if they are bad?

Click to expand...

Nope,... No test needed,... Those are a Bad design, that suffered production problems...

It's a minor Miracle if yer's aren't breached yet...

Like Don said, convert it to the 2 piece system... yer on borrowed time...

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Sounds like a plan... Thanks for all the advice guys!

Re: Hydrolocked 4.3L, Exhaust Manifold's, intake or both??

Just for a lil bump in confidence I knew nothing about boats or boating 3 weeks ago and now have taken a hydro locked motor with a bad cylinder head and head gasket and stripped her down.bare bones and rebuilt it..u can do it np