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305 chevy mercruiser 228 hp inboard 1982 fresh water cooled

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chasmans

New member
I have a 305 mercruiser that is overheating. Have changed the manifolds and risers , sea pump t-stat . I ran over some mud 10 years ago and the overheating started. I havn't used the boat since then. This year I flushed the engine out replace those parts and sit still overheated. My Mechanic took out the stainless steel restrictor plate in the riser and it still overheated. Should I be using the restrictor plate in the riser ? Mechanic says they are only used in the closed water systems . The restrictor plate originally had a small hole in it and it ran cool years ago befor I had the overheating problems. I havnt replaced the water pump yet although I did replace it in 2004 when repowered the boat. I have twin inboards and the other motor when I took it out 10 years ago didn't overheat at all . It now does over heat and we are going to take the restrictor plates out. This engines timing is off , can that cause overheating ? Do I need the restrictor plates ?
 
I assume that when you headlined "fresh water cooled" you meant that the boat ran in fresh, not sea water????

1) Find another mechanic.
2) Restrictor plates used in closed cooling systems do not have ANY HOLES in them. Restrictor plates with small holes in them are used in raw water cooled systems to prevent overcooling of the exhaust manifolds. These are known as "warm manifold" systems.
3) I assume that your engine did not overheat with the plates with small restrictor holes in them before you ran into a mudbank, right? Soooo... why would you modify the engine by changing the restrictor plates when what you needed to do was fix what ever damage or degradation happened to the engine from running in to mud???
4) Running into mud or sand or gravel, i.e., ANYTHING but water is not good for the raw water pump impeller or ofthen for the housing itself.
5) Engine timing... did the timing get changed after or as a result of the encounter with the mud? IF not.... timeing off not good but as I said..... fix what went wrong when you hit the mud.
6) Find another mechanic. This one lacks some basic knowledge about marine engines.
 
Before the mud , when it ran cool , the restrictor plates had a tiny hole in one of the sides . It was run in brackish water . When I replaced all the manifolds and risers the kit came with no holed restrictor plates . The engines did run cool before the mud. Is the timing different for counter rotating engines ? The timing is off due to someone playing around with it without a timing light after the mud.

He works cheap and no marina wanted to work on the boat due to it's age ect. I have been through a couple of mechanics who essentially ripped me off. Guys I found on Craigs list . This guy got his info from a marina parts store.
 
In my opinion, the term "Fresh Water Cooled" is somewhat of a misnomer. Please clarify!
When you say "fresh water cooled", are you refering to operating in river or lake water...... or are you refering to your Engine being equipped with a "Closed Cooling System"?

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chasmans said:
I have a 305 mercruiser that is overheating. Have changed the manifolds and risers , sea pump t-stat . I ran over some mud 10 years ago and the overheating started. I havn't used the boat since then. This year I flushed the engine out replace those parts and sit still overheated.
If this Engine is truly fitted with a Closed Cooling System, I would need to ask you if the seawater side of the heat exchanger was cleaned after the "mud" incident?

My Mechanic took out the stainless steel restrictor plate in the riser and it still overheated.
Yes...... find another mechanic who understands why the SS restrictor plates were installed in the first place.

Should I be using the restrictor plate in the riser ?
Again.... can you clarify as to the SS restrictor plate being installed underneath a Riser/Spacer or underneath an actual Elbow?
(the two are not the same part)


Mechanic says they are only used in the closed water systems . The restrictor plate originally had a small hole in it and it ran cool years ago befor I had the overheating problems.
I must assume that your system is either an "open" system, or is a "Half Closed Cooling System". (engine only)

When a SS restrictor plate (one with the weep hole) is used, the exhaust manifold is typically supplied with seawater at one end, and will have a seawater exit at the other end. (the seawater transfer ports are NOT used)

The exiting seawater then enters the Elbow via an additional port.

The weep hole in the SS plate is there to allow draining for Winterizing.

Now....... if your exhaust manifolds are equipped with a fitting at one end only..... then the seawater transfer ports must be fully open.


I havnt replaced the water pump yet although I did replace it in 2004 when repowered the boat.
Which pump are you speaking of?
I ask because some call the "Engine Circulating" pump a water pump.
Are you speaking about the "Circ Pump", or the "seawater pump"?
I have twin inboards and the other motor when I took it out 10 years ago didn't overheat at all . It now does over heat and we are going to take the restrictor plates out. This engine's timing is off , can that cause overheating ?
You bet it can...... and it may not stop at that!


Do I need the restrictor plates ?
As said...... if your exhaust manifolds use the seawater transfer ports to supply seawater to the Exhaust Elbows, then NO..... the transfer ports MUST be fully open.
If your exhaust manifolds are fitted with a seawater supply and a seawater outlet that runs to the Elbow, then yes, it is likely that Merc wants the SS restrictor plates installed.

Find your Engine model number and look up your cooling system schematic.
Click to expand...
 
chasmans said:
Before the mud , when it ran cool , the restrictor plates had a tiny hole in one of the sides . It was run in brackish water . When I replaced all the manifolds and risers the kit came with no holed restrictor plates . The engines did run cool before the mud. Is the timing different for counter rotating engines ? The timing is off due to someone playing around with it without a timing light after the mud.

He works cheap and no marina wanted to work on the boat due to it's age ect. I have been through a couple of mechanics who essentially ripped me off. Guys I found on Craigs list . This guy got his info from a marina parts store.
Click to expand...

One of your problems is the words you are using to describe your parts................so expect some back lash until the right info is eventually ripped out of you.


Closed cooling = heat exchanger and the use of antifreeze like in a Auto
Fresh water/Raw water = no heat exchanger or antifreeze and uses only raw water to cool engine and manifolds/elbows.

Restrictor plate = plate with holes in it

Block off plate = Plate with no holes in it to BLOCK OFF




If the parts you purchased came with a fully closed restrictor plate (BLOCK OFF PLATE) then that is wrong and your guy is right!

A non (closed cooling) system or Raw water system uses a restrictor plate as you describe. One with small holes in them. Get the correct ones.

The fact here is you have not used the boat for a very long time....................replace the water pump impeller first!!!!!!!!!!!!!!!! Sitting in a compressed state in the water pump housing for an extended has ruined it and it may have rotted and now has broken vanes. If you have then disregard!!

Remove the incoming water hose from thermostat housing And back flush system to make sure nothing is clogging the water in path. if you have a engine mounted water pump impeller then remove the hose going from pump to t stat housing. Should be a power steering cooler inline. Maybe that is clogged??

After correct restrictor plates are installed and new impeller installed if needed and you can confirm un interrupted water flow into engine report back.
 
kghost said:
One of your problems is the words you are using to describe your parts................ so expect some back lash until the right info is eventually ripped out of you.
Click to expand...

Although the delivery could use some softening........... I must agree with Jack on this one. :)
When we all speak the correct Marine terminology, it makes communication so much easier.


.
 
thanks guys . I will try a few things and let you know how it turns out. I will try to reply with correct terminology . Chasmans
 
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