What do I check after a SHT with my'88 mercruiser 3.7lx

[boltonranger]

Ok; so here it is.
Rolled out the boat and put it on the muffs to run the motor and check things out.
About 18 months ago I replaced the water pump seals but haven't been on the water since.

So there I am - water pressure at the muffs and after checking all the fluid levels
(Closed coolant system was full, yay.)

I crank it over and it starts.
A little shaky at first, always has been.
Smooths out some and it seems a little loud.

I shut it down and hop out.
Water's on alright.

OK so I hop back in and fire her up again. This time I see water running from the motor box towards the bow!
So I kill the engine and raise the motor cover.
Hmmmm.
Ah! There it is.
I failed to re-attach the lower portion of the oil cooler hose to the freshwater HEX outlet.
I usually don't drain the cooler - but for some reason I had done it many months ago.


So I attach the hose and clamp it.
Start the engine warily.
All good.
Ran on the muffs fine etc.
Never overheated - temp was normal.

So after this incident I began thinking...
Is there anything else I should check?

The boat probably ran less than 2 minutes without the hose on there - that's not to say the hose and hex weren't somewhat lined up -my realization of it all
happened so quickly that I can't recall for sure how well or not well they aligned;
IOW whether water was actually making it to the exhaust elbow or not.
Just can't recall for sure. I do know there was water at the impeller. That's certain.

Soooo... what should I check now?
Bear in mind I did run it for some time after I attached the hose.
Exhaust water generally came out the left and right sides of the out drive and a small amount out the prop.
It all seemed normal; just thought I'd pass it by you folks and see what you thought.
Thanks in advance;
-br

 

[achris]

Re: What do I check after a SHT with my'88 mercruiser 3.7lx

I'd say that you are one lucky SOB ... With water running through the pump and water pocket cover (in the lower part of the upper drive) it will have kept the temperatures of the plastic parts low enough for them not to have been affected....

The only part that I would be the most concerned about would be the exhaust shutter, but they are usually gone in the normal course of events anyway.... Just check/replace it when you next have the elbow off....

Chris.......

 

[boltonranger]

Re: What do I check after a SHT with my'88 mercruiser 3.7lx

Well thank you for the reply Chris;
So if I read you right - the internals of the outdrive were cooled by the water going in through the muffs
(and out in my bilge.)

So the shutter may have gotten hot.
I have never looked at the shutter I don't think ever.

Now I guess this is a good time to ask this -

- When I hook up the muffs I have always opened the spigot at the house alot and water
will spray out the edges of the muffs when the motor is not running.

So here's question no. 1 - "Am I correct to open the faucet so much or should it be lesser pressure / volume?"

Since we're talking about the water flow - Here's questions 2 & 3:


The water that sprays out at the muffs with the motor off is obviously being "stopped"...

"What prevents that water from traveling all the way up through the HEX and into the engine exhaust manifold?"

"Is it simply the impeller in the lower outdrive "not rotating" that holds the water back?"

Lastly - You mentioned that most shutters are "gone."

Can you elaborate?

I really appreciate your help.
-br

 

[achris]

Re: What do I check after a SHT with my'88 mercruiser 3.7lx

Question 1. Full volume. When that engine is running at just 1000rpm the pump needs a MINIMUM of 12 litres per minute.
Question 2. You answered that yourself...
Question 3. Apart from the late models, about 1996 and later, most of the shutters were either burned up by the exhaust or wore through the shaft and fell out. The later model design really does work. I put a set in the old engine in '97 and they're still working just fine. The reason for the shutters is to slow any water that could be forced back up the exhaust system and into the engine. That can happen if you were to pull the throttle back and kill the engine at the same time, or if a large wave were to hit the back of the boat without the engine running.

HTH,

Chris.......