Overheating issue…

[OceanRipples]

Hi, I have just purchased a boat with a 4.3L LX Merceuiser V6 (petrol). I’ve done a sea trial in the boat and everything was fine. I’ve just run up the boat on the driveway using a hose and earmuffs, which seemed to seal well around the leg, and after five minutes or so running I had to turn off the engine because the water temperature was v high. Does anyone know why this has occurred? It’s almost as though the thermostat did not open, although I can’t imagine that’s the problem as it was fine one week ago. Is there an inherent issue of engine overheating when using earmuffs on a hosepipe? Image attached. Water did seem to be coming out of the leg, so it was definitely getting a level of cooling going though. Does anyone even know where I can locate the thermostat?

 

[BruceK]

here:

Also see the checkballs. If they are loose then overheating at idle can be a problem
Also check when your thermostat opens. IIRC should be at 140F/60C. Quite low as thermostats go.

 

[OceanRipples]

here:

Also see the checkballs. If they are loose then overheating at idle can be a problem
Also check when your thermostat opens. IIRC should be at 140F/60C. Quite low as thermostats go.

Thank you! Out of interest what do those balls do? When you say check they are not loose, do you mean that they don’t slide up and down the rod? Also, how do I check/know when the thermostat has opened?

 

[BruceK]

Also, how do I check/know when the thermostat has opened?

difficult if you dont have a thermometer for it. Just replace with one for your engine from a dealer.

Out of interest what do those balls do?

Control waterflow on bypass


Types of thermostat housing depend on age of engine (note there are various grades of thermostat so check with dealer which one your engine should open at)

knock yourself out.......................

 

[OceanRipples]

difficult if you dont have a thermometer for it. Just replace with one for your engine from a dealer.



Control waterflow on bypass


Types of thermostat housing depend on age of engine (note there are various grades of thermostat so check with dealer which one your engine should open at)

knock yourself out.......................

Thank you, super helpful links also, thanks a lot!

 

[OceanRipples]

Could it be that the boat is overheating because the hosepipe doesn’t provide enough water flow for the engine?

 

[oldgit]

When were the risers last replaced/checked.
Check risers next ? Not that difficult a job and needs to be done out of the water.
Traces of rust around the riser to engine block connection , a warning sign.
The four bolts can be a pig to get at as well. heat and lots of release fluid will help.

 

[OceanRipples]

When were the risers last replaced/checked.
Check risers next ? Not that difficult a job and needs to be done out of the water.
Traces of rust around the riser to engine block connection , a warning sign.
The four bolts can be a pig to get at as well. heat and lots of release fluid will help.

Thanks!

 

[colhel]

Could it be that the boat is overheating because the hosepipe doesn’t provide enough water flow for the engine?

I'm not an outdrive person, but from what I've been told, those muff things are meant to rinse fresh water through and don't provide enough water to maintain temperature.

 

[Mr Googler]

If everything ran fine on sea trail it could just be lack of water flow via the hose route for sure

 

[OceanRipples]

If everything ran fine on sea trail it could just be lack of water flow via the hose route for sure

Thank you, the more I talk to people I get the impression that is the case, I simply isn’t enough water and pressure to circulate the engine properly. These ear-muffs are clearly just for rinsing briefly.

 

[stelican]

Thank you, the more I talk to people I get the impression that is the case, I simply isn’t enough water and pressure to circulate the engine properly. These ear-muffs are clearly just for rinsing briefly.

You can normally run engine on muffs for extended periods if they are a good fit.I have done this many times.

 

[Jamie Dundee]

You can normally run engine on muffs for extended periods if they are a good fit.I have done this many times.

They do need to be double sided muffs on a bigger engine though.

 

[AndieMac]

They do need to be double sided muffs on a bigger engine though.

Yes, agree with this comment, with a good tight fit around the intake strainer, good water pressure of course the engine running at idle revs only.

I’ve seen cases where the unsuspecting operator wanders off allowing the rinsing process to run its course, and the weight of the hose pipe coming up from the ground on loose fitting muffs (or an imperfect push-on hose fitting), and water pressure, drag the muffs away from the outdrive and an overheat develops.
I used to run the hose pipe up behind the trim tab rams then down to the strainer/inlet and muffs, to support the weight of the hose where it connects to the muffs.

 

[OceanRipples]

Yes, agree with this comment, with a good tight fit around the intake strainer, good water pressure of course the engine running at idle revs only.

I’ve seen cases where the unsuspecting operator wanders off allowing the rinsing process to run its course, and the weight of the hose pipe coming up from the ground on loose fitting muffs (or an imperfect push-on hose fitting), and water pressure, drag the muffs away from the outdrive and an overheat develops.
I used to run the hose pipe up behind the trim tab rams then down to the strainer/inlet and muffs, to support the weight of the hose where it connects to the muffs.

The pressure is good on our hose and the fit is tight but still leaks out the muffs due to the pressure of the water. I have the double sided inlet muffs. See attached. Yes, I imagine walking off and leaving this is not a good practice! ?