Boat overheating

T

TGofers

Member
Changed pump, thermostat, impeller, belt, cleaned manifold risers, elbows look fine. Can't get any water to the manifolds. They overheat. What am I missing? Heat exchanger engine coolant stays cool but raw water gets hot. Very little water pumping out of leg. Any thoughts?

Also can you move this post to the boat, trailer sub forum please
 
Last edited by a moderator:
What engine/leg are we talking about? From the very brief description you've given, its pretty tough to diagnose.
A quick thought that comes to mind that MAY encompass SOME engine/drive combos.....What about the circulation (water) pump that is bolted to the engine block?
 
Last edited by a moderator:
I'm thinking a plug of some sort in the heat exchanger itself. Or, perhaps when you hooked up all the hoses again you put the raw water hose (to the heat exchanger) on the wrong inlet on the heat exchanger? I'm assuming you have an external heat exchanger like my old 3.0 L Mercruiser had.
 
You say cleaned manifold and risers! What exactly does that mean, how old are they? I would bet you have a partly plugged manifold or riser that is not letting the raw water thru or perhaps like rock dog stated it could be a raw water pump flow issue.
 
So. Spoke with Tyler at Breakwater marine and he seemed to be the only guy not trying to sell me parts in this whole entire mess. looks like there is some hose from drive to stern that wears easily. I started up the beast and pulled the hose from the pump to the exchanger and barley any water pushing out.. Just spitting. The hose from the drive to stern has a very week cupped/fitting and is usually the first to go. Tyler or Tyson at breakwater said to try that first, and that should of been my first step but I was given other advice so now I have new parts!! Not too upset as the impeller and pump and belt all should of been replaced and the manifold gaskets and thermometer gaskets needed replacing as well. I will call breakwater in the am and see what part it is I need and keep you all posted.
Lesson learned, pull the pump hose leading to the heat exchanger and start it up and if not pumping work your way back to the drive... For future reference! Any one know what part Breakwater is referring too?
 
TGofers said:
So. Spoke with Tyler at Breakwater marine and he seemed to be the only guy not trying to sell me parts in this whole entire mess. looks like there is some hose from drive to stern that wears easily. I started up the beast and pulled the hose from the pump to the exchanger and barley any water pushing out.. Just spitting. The hose from the drive to stern has a very week cupped/fitting and is usually the first to go. Tyler or Tyson at breakwater said to try that first, and that should of been my first step but I was given other advice so now I have new parts!! Not too upset as the impeller and pump and belt all should of been replaced and the manifold gaskets and thermometer gaskets needed replacing as well. I will call breakwater in the am and see what part it is I need and keep you all posted.
Lesson learned, pull the pump hose leading to the heat exchanger and start it up and if not pumping work your way back to the drive... For future reference! Any one know what part Breakwater is referring too?
Click to expand...

You still have not said what engine/ leg you have. If it's a merc, there is an external hose from the lower leg to the transom housing. Hose is probably collapsed or folded over.
 
I'm watching this with keen interest. I'm also having a strange problem, with my Volvo AQ211 (chevy 305)/280. I have a raw water flow alarm that was going off, and the engine was overheating. I was overdue for an impeller, so I had Alpine marine throw a new one in while they were doing other work. Put her in the water, and she runs like a top but quickly overheats at anything over 3000 RPM. there is no 'flow alarm' going off this time, however. If there is good raw water flow, what could be causing the overheating? should I be checking the flow in the heat exchanger? How would I do that?
 
Oh where to begin??! I have a 270 volvo leg with the 302 Ford engine. The 280 leg is almost identical to a 270. You could start by simply buying a laser thermometer (they are cheap nowadays) and start shooting different areas on your engine and heat exchanger etc. to see where the heat is the most. Of course keep an eye on the temperature of things so you don't cook your engine.
It's a pretty simple system. The raw water pump which is either bolted to the crank or mounted seperately is belt driven. The impeller sucks up the water (you didn't happen to remove and replace the raw water pump because that can be mounted the wrong way where it doesn't suck water in, been there done that) the raw water then travels through your heat exchanger to absorb heat from the hot anti-freeze and then is expelled through the manifolds and risers. Simple as that. The other part of the cooling system is the engine side which consists of a circulating pump (on a car it is simply called the water pump). The circulating pump circulates the anti-freeze through the engine picking up heat and then travels through the heat exchanger where it transfers the heat to the raw water side. You have a thermostat which needs to operate properly as well as the circulating pump which needs to work properly. Check those as well. You can pressure test this system just like you would do in a car to see if there are any leaks.
I have heard once that I guy had overheating problems only when his boat was on plane. But when he slowed down to idle the temperature would come down. The problem there was there is a gasket on the intake neck on the outside on the leg (look at a schematic) When the boat came on plane the intake neck is out of the water...ergo the system starting sucking air and once that happens you start to overheat.
Worst case scenario for overheating problems would be that your boat engine didn't have fresh water cooling it's whole life. In other words it might have been raw water cooled which might have clogged some cooling passages in the engine itself. If that's the case the engines days are done. Just sayin'.. Otherwise start at the beginning and start trouble shooting.
I go to my local library and take out the Seloc and Clymer repair manuals. Very helpful.

Have fun!!
 
My heat exchanger has end cap. I always pull that and check when heating problem. Have had sand, rocks and seaweed blocking the passages. Have a jet drive, so the sand and rocks.
 
I took a hose and pumped water back out the drive. Leaking from the bottom bellow as well as the intake on the bottom of the leg. I guess that means I am sucking air somewhere from the leg to the intake raw pump hose. There is a hose that is between both bellows in the leg, wonky shaped, almost like an S. Apparently that might be my starting point. Only trouble is, getting to it! Looks like I have to take off the top half housing of my leg to get at it. Wish me luck!!
 
Those aren't leaks. Water can come out your exhaust bellows and water is coming out a hole at the bottom of the leg that is an additional intake point.
 
daddystoy said:
Those aren't leaks. Water can come out your exhaust bellows and water is coming out a hole at the bottom of the leg that is an additional intake point.
Click to expand...

Yes but should water be coming out my exhaust bellows when I am not even running water through the exhaust?? I just have a water hose stuffed in my pump hose and am pushing water in reverse to test if I am getting a leak other than the leg intake. the bottom exhaust bellow is dripping water significantly when I force water backwards. Seems wierd when I am bypassing the entire cooling system to test if I am getting air from the drive that water would be leaking out of the exhaust bellow. I have the risers off right now so water can't even get into the exhaust bellow via the manifolds.
 
Last edited by a moderator:
daddystoy said:
Oh where to begin??! I have a 270 volvo leg with the 302 Ford engine. The 280 leg is almost identical to a 270. You could start by simply buying a laser thermometer (they are cheap nowadays) and start shooting different areas on your engine and heat exchanger etc. to see where the heat is the most. Of course keep an eye on the temperature of things so you don't cook your engine.
It's a pretty simple system. The raw water pump which is either bolted to the crank or mounted seperately is belt driven. The impeller sucks up the water (you didn't happen to remove and replace the raw water pump because that can be mounted the wrong way where it doesn't suck water in, been there done that) the raw water then travels through your heat exchanger to absorb heat from the hot anti-freeze and then is expelled through the manifolds and risers. Simple as that. The other part of the cooling system is the engine side which consists of a circulating pump (on a car it is simply called the water pump). The circulating pump circulates the anti-freeze through the engine picking up heat and then travels through the heat exchanger where it transfers the heat to the raw water side. You have a thermostat which needs to operate properly as well as the circulating pump which needs to work properly. Check those as well. You can pressure test this system just like you would do in a car to see if there are any leaks.
I have heard once that I guy had overheating problems only when his boat was on plane. But when he slowed down to idle the temperature would come down. The problem there was there is a gasket on the intake neck on the outside on the leg (look at a schematic) When the boat came on plane the intake neck is out of the water...ergo the system starting sucking air and once that happens you start to overheat.
Worst case scenario for overheating problems would be that your boat engine didn't have fresh water cooling it's whole life. In other words it might have been raw water cooled which might have clogged some cooling passages in the engine itself. If that's the case the engines days are done. Just sayin'.. Otherwise start at the beginning and start trouble shooting.
I go to my local library and take out the Seloc and Clymer repair manuals. Very helpful.

Have fun!!
Click to expand...

Awesome. thank you very much.
 
have heard once that I guy had overheating problems only when his boat was on plane. But when he slowed down to idle the temperature would come down. The problem there was there is a gasket on the intake neck on the outside on the leg (look at a schematic) When the boat came on plane the intake neck is out of the water...ergo the system starting sucking air and once that happens you start to overheat

. ... that was my problem , but it was the flange was eaten away and the hose would collapse when the boat was up to around 4500 rpm ... back off the throttle .. and the temp went down ...
 
TGofers said:
Ii have it on a trailer in a bucket. So idiling
Click to expand...
I hope that's a "BIG" bucket otherwise you are just sucking up "HOT" water better to have muffs and cold water. Check the outlet side of the pump first to make sure you are sucking water first. If no water the impeller is done and needs replacing. If there is no water spitting out the leg with the muffs on there is a blockage up stream of the pump. If all that is ok, it's on the engine cooling side and most likely the thermostat.
 
peetz said:
have heard once that I guy had overheating problems only when his boat was on plane. But when he slowed down to idle the temperature would come down. The problem there was there is a gasket on the intake neck on the outside on the leg (look at a schematic) When the boat came on plane the intake neck is out of the water...ergo the system starting sucking air and once that happens you start to overheat

. ... that was my problem , but it was the flange was eaten away and the hose would collapse when the boat was up to around 4500 rpm ... back off the throttle .. and the temp went down ...
Click to expand...

Can you elaborate on where this flange is, and how I might determine if this is the problem?
 
You must log in or register to reply here.

Similar threads

K
Raw water flow, Mercruiser 470
Replies
11
Views
1K
Kolbads
K
Z
1991 23ft bayliner trophy
Replies
4
Views
833
DuroBoat
D
F
21.6 Glassply
Replies
3
Views
1K
fahcups
F
ab1752
Sierra Manifolds and Risers after 350 Hours
Replies
7
Views
838
SpringVelocity
SpringVelocity
Sandpiper
Help pricing Motor and Leg
Replies
0
Views
344
Sandpiper
Sandpiper
Back
Top