Have no idea what happened!!! Need Help!!

[baldwin84]

Ok I have a Bayliner I/O with a 87 GM 305 5.0L I recently took the exhaust manifolds and heat risers off to clean them due to a blockage resulting in the engine overheating. They came pretty clean and I re-installed everything today and took the boat for a spin. While wide open the temp reached 175 F so the over heating issue was resolved. While on my second pass I noticed large amounts of smoke coming from the engine. When I opened the compartment I also noticed the left exhaust boot which meets the heat riser was sizzling with heat, almost like flames were coming out the manifold and started to melt the boot. What in the world could cause this, prior to this it was only overheating. I don't think it matters but the thermostat was taken out and not replaced just because I have haven't bought one yet. Any Ideas?

 

[Bondo]

Re: Have no idea what happened!!! Need Help!!

Ayuh,.....

The Damage was already started back with the 1st Over-Heat....

You give very little Info about just What it's got for a Driveline....
So,...
I venture a Guess that removing the T-Stat has caused an imbalance in the cooling system,...
Water takes the path of least resistence,....
My Guess is,... The other side of the motor dumped ALL of the water....

Btw,....
Cleaning Rotten manifolds is the recipe for a Motor Replacement.......

 

[baldwin84]

Re: Have no idea what happened!!! Need Help!!

I' sorry it is an OMC 5.0L 305 with a Cobra 2 outdrive. The Manifolds and Risers are log style and the risers sit in the back. The manifolds weren't bad at all I just cleaned them for giggles. The risers on the other hand were bad. If I had the money I would have just got new ones. So if I replace the T-stat it should fix the problem? And why is cleaning the manifolds bad?

 

[Bondo]

Re: Have no idea what happened!!! Need Help!!

it is an OMC 5.0L 305 with a Cobra 2 outdrive. So if I replace the T-stat it should fix the problem? And why is cleaning the manifolds bad?

Ayuh,.... I don't do OMCs,...

But I'd Still put the T-Stat back where it belongs......

When you Clean manifolds,+ risers,... The Junk that you're Digging out of them,.?.?.?.?.
Used to be Cast Iron,..... It's No longer there,.....

It's only a matter of Time,....
The Ocean will be pouring into your motor.......

 

[Don S]

Re: Have no idea what happened!!! Need Help!!

When manifolds start overheating because they are plugged up, that is the warning that it's time for new manifolds. The next thing that happens when cleaned is a hole develops in thin spots and water gets into your engine. If salt water. Say good buy to your engine, unless you catch it immediatly (within the hour) if it sets over the weekend or longer before you try it again. It will be rusted/locked solid and total junk (IF in salt water) you get more of a chance in fresh water, but fresh water doesn't usually plug up manifolds either.

 

[baldwin84]

Re: Have no idea what happened!!! Need Help!!

Oh well the manifolds were fine and this is only fresh water now.

 

[Don S]

Re: Have no idea what happened!!! Need Help!!

Oh well the manifolds were fine and this is only fresh water now.

If they used to be in salt water, the damage was done, going to fresh water doesn't heal them.

 

[Bondo]

Re: Have no idea what happened!!! Need Help!!

Ayuh,....

Good Luck,..... You're Flirting with Disaster.....

 

[baldwin84]

Re: Have no idea what happened!!! Need Help!!

Either way is the T-stat my problem, cause the housing has a T connection after the T-stat so I don't think it would matter. Plus I pulled the T-stat on my previous boat, which was exactly the same, and it ran better. HAHA Any other ideas?

 

[Bondo]

Re: Have no idea what happened!!! Need Help!!

Plus I pulled the T-stat on my previous boat, which was exactly the same, and it ran better. HAHA Any other ideas?

Ayuh,.....

It seems You've already got all the Answers,... Why even ask the Questions......

 

[chiefalen]

Re: Have no idea what happened!!! Need Help!!

Dear sir; I subscribe to the old school of mechanix myself. But engines are

designed to run at a certain temp. Your boat maybe 160-180 I really didn't look

it up. Nor do I intend to. Bye removing the t-stat your just asking for

trouble. And you just alienated the best mechanical minds here.

 

[jerryjerry05]

Re: Have no idea what happened!!! Need Help!!

Just because you "cleaned" the risers and the manifolds doesn't mean you fixed the problem.If they are bad enough to be cleaned they should be replaced.You got 20 years from them and thats good.The thermostat is there to control flow.If you remove it then your engine will not cool correctly.You can have hotspots and burned hoses.
Bite the bullet and get risers and manifolds and you can probably get another 15-20years.
Heat and hot water start the corrosion and AIR finishes the job.
Everytime you shut off your motor and the water leaks down the rot continues. Flush with fresh water and it will slow it some.Jerry

 

[bamadave]

Re: Have no idea what happened!!! Need Help!!

The pro's have told you the remedy. The choice is yours. Cure it or kill it, depends on you what you do next.

 

[Maclin]

Re: Have no idea what happened!!! Need Help!!

Without a thermostat the cooling water can run thru the enigne too fast and not absorb as much heat, the engine can actually run warmer.