Trojan Boat Forum

Hello - I am new to this Forum

I have a 1973 31ft Trojan Boat. She has twin 318 Chryslers 225hp engines.
Raw water cooled

She has an overheating problem on her portside engine.

Both Exhaust manifolds are overheating,too hot to touch. The engine is being run without the thermostat in order to check water flow. There is water being pumped out the rear exhaust,but not much. The Sherwood Pump, dual ports has two new Impellars. CW turning pulley - Impellars turning CCW

This is not a LM engine but I believe a LA engine

Before I can go any further in trying to diagnoes this problem I need to find a Cooling Diagram or Schematic. I cannot find one anywhere.

I am trying to figure out how the Water flows from the Water Pump to the Thermostat thru the water passages in the block and water pump housing.

Any replies will be greatly appreciated

Here is the typical marine V8 coolant flow. How old are the manifolds and risers? How about a clogged seacock, trans cooler? Oh...and welcome aboard!

Fresh Water:



Raw Water:

If you Have the LA 318 engines the photos here will help .look at the photo on page 7 . That is a LA .

http://www.correctcraftfan.com/Download ... Manual.pdf


Being that the boat is a 73 and the engine is 225 hp I belive you have a LM318 if this is the case .this may help some .What makes you think its a LA not a LM ?
http://www.correctcraftfan.com/Download ... Manual.pdf

Post a photo of the engine I would be happy to ID it

If you do not have a strainer betwen the seaclock and the transmission cooler you may have the cooler stopped up with debris. Water passes through this before the pump. The cooler looks like the end of a mini boiler with small pipes that pass through cooling the transmission. They are easily clogged and ergo water stopage to engine.

My engines had not thermostat in them bet it was for same reason you stated. the raw water hoses from seacock to transmission cooler wither absolutely fule of debris clogging water flow.

If no sea strainer check transmission cooler and its supply hose. In addition thermostates should be 140 to 142 degree.

I bet they were not the problem at the end of the day.

I would bet that ur exhaust manifolds and risers are bad. If there new and u still having problems I would look into ur actual engine block. If the boat was used in saltwater these are real possibilities. Hope this helps

I would bet that ur exhaust manifolds and risers are bad. If there new and u still having problems I would look into ur actual engine block. If the boat was used in saltwater these are real possibilities. Hope this helps

There are also copper tubes in each manifold that 6 holes in ech could be a stoppage. If no striner bet on stoppage at trans cooler. But you have to check all. I would start at easiest. IE water intake at sea cock.

Thankyou for all your replies

I checked the water discharge from each rear exhaust. The port side is about half that of the stbd.However I believe that the Water Pump and its new Impellars is working.

I have inspected every hose and its condition. (replaced a couple)

Flused the cooling system including the Oil Cooler. Both Exh manifolds are hot so I have ruled out a single Manifold This tells me that there is one single problem
This is not a LM engine. Mine do not have a Circulating Pump. Water flows from the Seacock (no Strainer) to the Water Pump inlet. It goes out thru a 90 deg hose to the Water Pump Housing

I am not sure what happens from this point. Inside the Pump Housing there are water passages thru the Timing Chain cover. One to the right Cylinder Head and one to the left side

Before I go any further I would appreciate some information about the Sherwood Water Pump.
Could improperly installed Impellars still pump water what ever the amount.
Could I have installed the pump upside down.
The Pump Pulley turns CW - With the Pump dismantled and looking at the rear of the first Impellar ist Vanes rotate CCW - The draining screws point towards the hull (opposite that of the Stbd pump.)

Your efforts are appreciated

They can be mounted upside down and wont work properly. I assume you have a single cavity, Sherwood G5, G6, or G7.

http://www.sherwoodpumps.com/en-us/Prod ... rature.htm

This may help as it is confusing.

Just a note early LM 318 did not use a Circulating Pump as some early big block also did not use a Circulating Pump.

I will keep look for better Diagrams of the cooling systems


there is a Diagram on page 18

http://www.correctcraftfan.com/Download ... Manual.pdf

if it is a raw water and does have a circulating pump the flow is raw water in lower circulating pump hose and out the two side pump ports, water circulates through the engine and returns via top hose from thermostat housing. I researched the pump figuring how to heat a water heater. Hot water will flow out the thermostat housing mix with raw water regulated by the thermostate. Any water returning is inserted at front of pump into impeller weather from thermostate or in my case hose coming back from hot weater heater. Also excess raw water not needed in the engine is pumped overboard cooling the headers etc.

If it does not have a circulating pump, I do not have a clue. Some one posted the 318 water flow diagram, and I have it and will scan and post a pic, but that would be for 318 raw water cooled with a circulating pump.

One other thing to check is the intake hose make sure its not collapsing when running , that will restrict the water flow

Welcome aboard.

i have to go with what Larry says, Im about 2 or 3 weeks away from bench testing his motor with the water system wooohoooo.

Bluewater, your water cooling system sound like the same as my boat although I have Chrysler 280hp (M400) in my 73 tri cabin. I have D55 dual impeller sherwood pumps. To know if your pump is mounted properly, look at the pump housing, there are arrows with descriptions in the casting that tells you which connection is inlet and outlet based on the pump rotation. I do think you'd overheat immediately though if it was on backwords. The Sherwood pump web site has a complete PDF drawing of the D55 pump and other pumps.