Heat Soak...Cowl Vents?

[KailiNoel]

Hi...I have been studying the posts on this forum for a few weeks and keep seeing the issue of heat soak coming up. I have a 1975 Johnson 115 and have been having the problems described by everyone else. Taking the boat out tomorrow and am going to try removing the cowl before I shut the motor down to drift. If this cures the problem, tomorrow night I am going to install some vents/louvers on the back of the engine cowl. I already bought them from west marine (approx 5 x 5 1/2 @ $5.99 each). Has anyone else tried this? It seems like such a simple fix....my only concern is upsetting the vaccum that the carbs use to draw air while the motor is running...any input/thoughts/suggestions would be appreciated. Oh, by the way, I am going to mount the vents on the back of the cowl with the louvres facing down to minimize the amount of water than can get into the engine compartment. The cowl has 3 "sides" on the back /-\ something like that and they will be on the angled sides, as high as possible. Thanks again....

 

[R.Johnson]

Re: Heat Soak...Cowl Vents?

These engines' are water cooled. They do not run very hot as compared to other water cooled engines'. They are not a pressurized system such as an auto. Venting the hood would have little, or no effect. These engines' are not finned, so air is not what carries away the heat. Painting the power head black would probably has as much effect as venting the hood. The hood is vented, allowing all the air the engine can use. Running without the hood would not effecy cooling, or performance.

 

[KailiNoel]

Re: Heat Soak...Cowl Vents?

Thank you for your response Admiral....sadly, your completely missing the point of my post. Removing the cowl has been proven to be a way to diagnos(?) and temporarely stop the effects of heat soak (if your not familiar with the condition there are a lot of posts on this site about it). I would like to hear from someone that has found a way to correct the problem. Im completely aware that the engines are water cooled and know how the cooling systems work....thanks again

 

[bktheking]

Re: Heat Soak...Cowl Vents?

You could install vents or cut a hole and run a small blower and pipe in something to move the hot air out. Is the system cooling properly?

 

[kenmyfam]

Re: Heat Soak...Cowl Vents?

Looking forward to more response on this one !!!

 

[KailiNoel]

Re: Heat Soak...Cowl Vents?

This is getting fustrating...the motor is perfect, it runs better than a new one would lol I am having the heat soak problem that 50 other people on this forum have spoken about. Ive done about a 150 hrs of research on the problem and everyone describes the same symptoms and offers the same technical explanations of what causes the condition, but I have yet to come across a single "real" solution. Ive read posts where people let the motor idol at a higher rpm for a few minutes before shutting it off or take the cowl off and let it run for a few minutes (even leaving the cowl off while they drift/fish). While these are great temporary fixes, they are not solutions. My gut feeling is that adding some vents to the cowel would let the hot air escape once the motor is shut off and its no longer being cooled by the water pump. Has anyone tried anything to find a permanent fix?

 

[R.Johnson]

Re: Heat Soak...Cowl Vents?

OK! What's heat soak?

 

[cannonford57]

Re: Heat Soak...Cowl Vents?

hi kail,if it were such an easy fix dont ya think someone would have came up with it before you stumbled across it?no disrespect intended....and as far as the clamshells your gonna mount on the rear of your cover goes,first hard shutdown and your going to see what engine cooling is all about....theres a reason the covers on v-4 johnson engines are sealed......a bunch of fellows smarter than me and yes you stayed up late a couple of nights and decided that was the best way to do it....i urge you to patent your idea because who knows,50 years from now ,someone might just utter the words..."Dang, that kail guy wuz darn sure smart.........."just my opinion.

 

[bktheking]

Re: Heat Soak...Cowl Vents?

Why don't you post what the symptoms are before assuming it's heatsoak. R.Johnson is right though, it's usually associated with a sealed cooling system rather than outboards but I like you have read posts talking about outboards as well.

 

[nymack66]

Re: Heat Soak...Cowl Vents?

Heat Soak case holds no water !
Heat Soak is just another excuse to alter an engine with the illusion it will work better.
All engines will experience this surge of internal temperature upon a abrupt or even graceful shutdown.
Have you ever noticed how many new cars overheats at a rest station on the highway? Reason is the abrupt shut down. The cure? Simply place the car in park and let it idle for at lease three minutes and watch the drop on your temp gauge then shut her off.
Same thing with an Outboard, Only on outboard the water caught in the Block is all it has to cool it off, which unfortunately is not enough, hence the rise in temperature. I know the exact numbers since I install dual probes port and starboard on my block.
Altering the Cowl is just like running the engine without the air baffle NOT recommended.
Here are some facts about my engine.
Idle (trolling) temp is 130/135 F
WOT 6k plus RPM 125/132 F
Abrupt shut-down IGN ON Motor OFF within 5 minutes 135/140 F

With that said Evinrude overheat alarm is design only to trigger at 175 F
So as you can see there is NO problem, the engine was design with this rise in temperature and will not harm anything.
Just my two cents for what's it worth.

 

[bob johnson]

Re: Heat Soak...Cowl Vents?

This is getting fustrating...the motor is perfect, it runs better than a new one would lol I am having the heat soak problem that 50 other people on this forum have spoken about. Ive done about a 150 hrs of research on the problem and everyone describes the same symptoms and offers the same technical explanations of what causes the condition, but I have yet to come across a single "real" solution. Ive read posts where people let the motor idol at a higher rpm for a few minutes before shutting it off or take the cowl off and let it run for a few minutes (even leaving the cowl off while they drift/fish). While these are great temporary fixes, they are not solutions. My gut feeling is that adding some vents to the cowel would let the hot air escape once the motor is shut off and its no longer being cooled by the water pump. Has anyone tried anything to find a permanent fix?

do you have a temp sender in each head?????

if so what are the temperatures of each head when you shut down????

my motors temps elevate at WOT but dont set off alarms maybe 160-180 on one head often, especially if the water temps are warm too...

but i never have experienced heat soak...my motor starts right up each time....

mid 90's V4

bob

 

[Silvertip]

Re: Heat Soak...Cowl Vents?

On an outboard no water is trapped in the block after shut down. It drains to the level of the water the engine is sitting in. They are self draining due a something called gravity! Heat soak occurs when the fuel in the float bowl of the carb boils to the point where it forms a vapor and spills into the intake manifold. On a car or I/O, that vapor finds its way "downward" where it then puddles in the cylinders with open valves or at the closed intake valves. Attempts to start the engine creates an immediate flooding situation unless you open the throttle to give the engine some air. On a carbed two stroke the intake manifold does not and cannot dump fuel or vapors into the cylinders because fuel entry into the engine is via the crankcase via the reed valves, then the transfer ports and then to the cylinder, all of which is "uphill". So I contend, since you haven't posted a symptom that you are not experiencing heat soak. Vapor lock maybe but I doubt that as well because under cowl temps on an outboard are not that high. Vapor lock prevents a fuel pump from pumping because the fuel in the fuel line has boiled creating a vapor bubble. Hot start issues on two strokes are almost always operator error involving non-use of the fast idle lever, over/under use of the choke/primer system or and engine that is simply in need of service. I suggest that float levels, defective needle & seat or other carb issues and/or weak spark are to blame and hot heat soak.

 

[bailey]

Re: Heat Soak...Cowl Vents?

Kaili if it will help put your mind at ease by all means add those vents and/or louvers to your hood. For all you experts didn't some of those mid 80's -150gt and 175gt come with louvers in the hoods,I seem to remember seeing them in this web site with regards to the outboard "drag racing". Some member here gave a "diy" essay on how he installs these.
Bailey

 

[bob johnson]

Re: Heat Soak...Cowl Vents?

Kaili if it will help put your mind at ease by all means add those vents and/or louvers to your hood. For all you experts didn't some of those mid 80's -150gt and 175gt come with louvers in the hoods,I seem to remember seeing them in this web site with regards to the outboard "drag racing". Some member here gave a "diy" essay on how he installs these.
Bailey

well my motor has the louvers on both sides up high at the back,

but they are chambered !!!!!!!
the opening goes backwards then inwards.....so while it is a source of air....water spashing does not go onto the motor!!

bob

 

[R.Johnson]

Re: Heat Soak...Cowl Vents?

An outboard engine is pulling in cold water all of the time. It does not cool the water, and recirculate it. Are you trying to scare yourself, or is something wrong with the cooling of the engine. Heat soak is a term used in the tempering of steel. This sound's like a case for a ten minute worry break.

 

[jonesg]

Re: Heat Soak...Cowl Vents?

Ethanol might be the problem, it boils off at lower temps.
Shutting down after a hot run without letting it idle first can leave residual heat that heats the carb bowls. Especially the metal ones.
SOlution is to let it idle and pump the bulb up to fill bowls with cold fuel.

I think adding loures without internal vents will lead to other problems like wet ignition wiring. And considering there is no airflow once the boat stops....

 

[kenmyfam]

Re: Heat Soak...Cowl Vents?

Seems like "much ado about nothing" ???

 

[boobie]

Re: Heat Soak...Cowl Vents?

I have been through the "heat soak" probs with the 60 degree omc's built in the 90's. I've never heard of a 1975 115hp having this problem. Got two suggestions. 1. find some fuel with no ethanol in it or 2. when you start it up after sitting use your choke and let it idle for two to five minutes. Then take off. Letting it idle "wets down" your carbs and intake system. Any fuel that is left in the intake manifold goes away when the motor is sitting hot after a hard run and sometimes fuel can "boil" out of the carbs and turn to vapor. I don't recommend cowl vents no matter which way they're pointed as you are just asking for more water injestion.

 

[bob johnson]

Re: Heat Soak...Cowl Vents?

wow I have a 95 115 60 degree motor and before that a 97 90 hp 60 degree motor and my motor starts up in a split second every time once out on the water.....of course I have run it a lot on dog summer days....

maybe i am lucky......

and my motor runs on the warm side.....

i know that when i tilt my motor for trailering and leave it like that in the yard, the gas seems to evaporate and i am left with the greenish 2 stroke oil running out of the carb opening into the inside of the colwing and out onto the transom bracket.....

then any dust sticks to is easily and my motor looks a mess!!

bob

 

[nymack66]

Re: Heat Soak...Cowl Vents?

wow I have a 95 115 60 degree motor and before that a 97 90 hp 60 degree motor and my motor starts up in a split second every time once out on the water.....of course I have run it a lot on dog summer days....

maybe i am lucky......

and my motor runs on the warm side.....

i know that when i tilt my motor for trailering and leave it like that in the yard, the gas seems to evaporate and i am left with the greenish 2 stroke oil running out of the carb opening into the inside of the colwing and out onto the transom bracket.....

then any dust sticks to is easily and my motor looks a mess!!

bob

I run mine in hells kitchen a place we call Orlando and never experience this heat soak, but you learn something new everyday I guess, I will now be on the lookout for the symptoms. If I do I will post it.
Bob as for excessive oil down the engine, remove all your re-circulation valves and clean them per your manual and change the gasket on the air cover you will NEVER see this oil again.