Smarty pants, I really could use your help! 350 Mag trouble SOLVED?? MAJOR UPDATE

Wildboating

Ok, they definitely are cracked.  Hooked water hose to bottom and plugged top holes on manifold.  Water is shooting through into exhaust chamber.  He said second one is same way. 

Wildboating

With the  gasket fiasco, later when I came back they said the open flow gasket was just sitting on the manifold, they produced another from the shop and said this was the other gasket. 

Handymans342

I see 3 different gaskets

Glassguy54

I can't see how you should be obligated to pay for all the screw ups of these incompetents.

Dude_Himself

Foolishly, about once every 5 years, I try to pay someone to do something I'm either unskilled at, unqualified for, or just don't want to deal with. It always ends up the same way, and typically after doing the work myself I realize where someone screwed up and figure out the solution.

That's why this thread is so sad - I'd have beaten someone to death with a wrench by now under similar circumstances. Poor @Wildboating has had a wild ride. I would start reaching out to anyone at Mercruiser I could to implore them to send a skilled engineer out to fix this. Their dealerships' failures to perform look bad on them too, independent ownership or not.

Wildboating

We are holding for Merc. Praying the will send someone

Black_Diamond

Must be one heck of a crack. 

Hope Al can chime in on the gasket issue.  I could see too much water flowing in could back flow.  The crack from hydraulic pressure from the engine.  Just my random .02. 

Wildboating

That’s what they are questioning too al.  I am seriously considering a complete Repower.  My wife and I are drained.  These $100 per hour techs and just constant trials are going to cost what new engines would.   I am terrified to buy two new fullly dressed motors and still have the same problem.


sorry for all the broken sentences and misspellings.  Typing on my iPhone seems to be a hit or miss for me lately. 

212rowboat

@Alswagg - he put new heads on the engine... unfastened manifolds suffer from harmonic imbalance, just like headers and/or manifolds on a car and will crack or straight up break at the point of support (collection or bend).  I am almost willing to drop some coin to wager those threads need chasing and the depth needs to be verified.  this connects all the dots throughout this thread with exception of the original failure... to be doubly so if the bolts were reused. 


@Wildboating

at this point, and I'm not playing:

purchase yourself a closed cooling system full kit.  go with wet joints as it makes zero difference once the system is split and closed, and the wet joints mucho cheaper with hella longer proof of concept behind them than dry.  

a full kit can be had off ebay for ~$1k.  the manifolds and risers can be had for a song.  sing to me- i have a complete set of brand spanking new wet joint manifolds, risers, and 3" spacers if needed.  get the full kit closed cooling system and put this behind you- I can send manifolds and risers/spacers for cost of shipping (and promise of return or replacement when i get around to rebuilding an engine i have sitting, which if i'm true to myself may be a few years... 

the advantages to closed cooling isn't as dramatic in fresh water as it is in salt, but.... you peg the thermostats rating and that is where it stays- period.  it'll take a couple hours each engine to install.  

put this crap behind you. 

dalek

Wildboating said:

That’s what they are questioning too al.  I am seriously considering a complete Repower.  My wife and I are drained.  These 100 hour techs and just constant trials are going to cost what new engines would.   Terrified to but two new fullly dressed motors and have the same problem still 

Don't throw the baby out with the bathwater.
Yet.

Wildboating

 Does anyone have a water flow diagram for 350 bags MPIMCM motor the motor has risers and is raw water cooled

Wildboating

I’m thinking there must be an obstruction somewhere in the water system

212rowboat

the only difference with this and yours is the dry joint... on the dry joint the water is stopped between the manifold and riser tower via gasket or plate... water is passed via a casting or pipe from exterior of the tower to the riser where it is spit into the exhaust stream.   

rasbury

212 has made a very good offer!

Wildboating

See the nipples pointing forward off the riser, mine has hose from each side coming down to a tee then into the water bulb on the bottom that runs through or collecting from cool fuel system. I did not realize the input was from the bottom of the manifold. 

Wildboating

And thank you for the offer, I’m going to look for an obstruction.  If I don’t find anything I will be reaching out to discuss this closed cooling solution.  

Wildboating

Could the riser be bad allowing water to fall though the dry joint and cracking the manifold internally?

212rowboat

my opinion... the only things that will break that manifold is heat focused on a bend area for a decent amount of time and/or temperature, harmonics, or bad casting to begin with.  the riser eaten/corroded through the jackets could allow water into the tower which could result in water in cylinders, but it isn't going to cause that crack in the manifold... 

The Main Exchange

Has the engine been removed and put on a dyno to check that it is producing full power? If not this may help to trouble shoot the power issue. Just a thought. 

Wildboating

Drew,

How can I spin the impeller pump without the engine running to verify that I have equal amounts of water coming out of both the starboard and port side exhaust manifold tubes. I want to disconnect them from the manifold and spin the impellers to see that we are getting equal amounts on both sides

212rowboat

You dont have to spin it.. Just pull the line that leaves the sea pump and stick a water hose in it.  Faucet pressure should be sufficient.  

Wildboating

BRILLIANT 

Wildboating

What about the thermostat when it’s closed

Wildboating

Should I just take it out

212rowboat

yup... pull it. 

Wildboating

At the end of last season around August I had boat pulled and both drives full serviced.  New seals, gimbals, shift cable the works.  Here is what my reservoir bottles look like. 

Wildboating

I just keep getting wrecked. 

pistole

Water in the drive oil?

J3ff

Mine looked worse than that this spring, sucked the crap out and replaced with fresh food, going good so far...

Black_Diamond

Dump out the oil from the reservoir. Flush out with mineral spirits or brake cleaner.  Refill with fresh fluid.