Mariner 40hp cooling system

Tim M · 19 April 2004, 18:33

I took my new Mariner 40hp out for a little ouoting today. Started it up, an a small but steady stream of cooling water came out of the tell-tale. After a little whilse it stopped all together. I stopped the engine, checked the water intake, and all seemed well. Started her up again, and same as before - small steady stream. Then same happened again - stopped after a short time (20/30 seconds maybe). The stream of water coming out when the dealer demostrighted it to me was much bigger (or so I remember).
Would I be right in saying that Mariner outboards have a thermostatic cooling system in them, so that the water will only really start pumping if the engine warms up (I did feel the cowling but this felt stone cold). The engine wasn't running for long in the end, as the water looked a bit too choppy when we got to the mouth of the harbour, so turned back.

swginn · 19 April 2004, 18:38

Don't know much about the actual cooling system, but caked up salt blocked the tell-tale on our old Merc 75 before. Always one to look out for!! Boy did we look stupid!!

Tim M · 19 April 2004, 18:40

I don't think it could be salt; the engine was demostraighted to me in a freshwater tank. That was the last time it was started before today.

tue · 19 April 2004, 18:45

Mariner do use a thermostatic cooling system on some of their outboards including some 40hps depending on age and type. Generally they don't show any water out of the tell tale untill the stat opens and allows the water to flow past. If the water is running a little bit then stops the cause is usually some crap in the tell tale pipe. Get something thin
(paper clip etc) and slide into tell tale when engine is running. Should unblock and pour out again.

Turbodiesel · 19 April 2004, 20:00

I would agree, the do tend to get bloked up with crap!!.
If it still stays bloked pull the hose off the fitting (inside the bottom cowl) and start it up you should get loads of water coming out.

Tim M · 19 April 2004, 20:06

Thanks for the advice; I'll give it a go.

Roughly how long will it take the cooling system to start pumping water from a cold start (given that this engine has a thermostaticly controlled cooling system)?

tue · 19 April 2004, 20:29

depending on the water temp and supply method (muffs or in sea) about 1-3 minutes.

Tim M · 19 April 2004, 20:57

I just took the pipe off, and it was full of crap - that would explain the problem!

ribfreak · 19 April 2004, 22:38

Hi Tim,

I`ve been using a 15hp Merc last summer and that bitch behaved exactly like in your description! It showed a good beam at the start and suddenly it cut it down to zero- nothing out of the pisser anymore and my pulse-rate up in the red- panic! Motor still running fine though.... Just when I jumped to the stern to kill that sucker it started pissing out some little drops and then a steady beam again- got used to it finally, but it`s not the way I`d engineer it..... you`ve got to grow some nerves to stand it! My horror always was: What, when the beam doesn´t come back this time?! I have to admit that this motor only did so at idle speed or with very low rpm`s- when I brought it up to at least 1/3 throttle this behaviour stopped completly and I had the steady beam all the time.
greetings,
Wolfgang

Tim M · 20 April 2004, 10:31

I too think the design of the tell-tale of very stupid; the pipe that feeds the hole is quite big, maybe 10mm, but the hole on the end is only about 3 or 4! What's that point in having such a tiny hole????

Mike B · 20 April 2004, 10:51

My Suzuki has to have the worst designed tell tale I have seen. It is continuously getting blocked and really is a bit pointless as I tend to take very little notice of it.

Even though it was fully serviced at the beguining of the year, including boring out the tell tale to try and stop the problem, within half an hour of its first run it was blocked, it used to give me regular heart attacks when it stopped but now I have got used to watching the water exhaust to ensure the cooling is working and relying on the overheat buzzer and cut out to warn me if the system did fail (it never has yet).

BMA · 20 April 2004, 11:34

Quote:

Originally Posted by ribfreak

Hi Tim,

I`ve been using a 15hp Merc last summer and that bitch behaved exactly like in your description! It showed a good beam at the start and suddenly it cut it down to zero- nothing out of the pisser anymore and my pulse-rate up in the red- panic! Motor still running fine though.... Just when I jumped to the stern to kill that sucker it started pissing out some little drops and then a steady beam again- got used to it finally, but it`s not the way I`d engineer it..... you`ve got to grow some nerves to stand it! My horror always was: What, when the beam doesn´t come back this time?! I have to admit that this motor only did so at idle speed or with very low rpm`s- when I brought it up to at least 1/3 throttle this behaviour stopped completly and I had the steady beam all the time.
greetings,
Wolfgang

My 200 Doesn't pump any water at all until the stat opens. It took me 3 goes before I plucked up the courage to let it warm up a bit

Nick Hearne · 20 April 2004, 11:56

Starting my old Johnson up for the first time last season I was rather worried not to see the tell tail for that seemed ages! Having understood that running with out water for 5 seconds was long enough to cook the engine! I was just a little bit concerned, should I shut down & get to a mechanic ASAP or keep my nerve. Well it did start after what seemed ages but was probably no time at all though it was certainly longer than 5 seconds!
Nick

Mike B · 20 April 2004, 12:15

Quote:

Originally Posted by Nick Hearne

Having understood that running with out water for 5 seconds was long enough to cook the engine!

Not sure about this, but I am sure someone more qualified will correct me if I'm wrong. I don't think 5 secs without water will "cook the engine". If the water is not getting to the impellor it is likely to damage that but not the engine itself. Damage to the engine would only happen when the engine temp got upto a high level. Presumably in most modern engines this would trip the over heat warning (hopefully before too much damage takes place).

Bilge Rat · 20 April 2004, 12:28

Quote:

Originally Posted by Mike B

Not sure about this, but I am sure someone more qualified will correct me if I'm wrong. I don't think 5 secs without water will "cook the engine". If the water is not getting to the impellor it is likely to damage that but not the engine itself. Damage to the engine would only happen when the engine temp got upto a high level. Presumably in most modern engines this would trip the over heat warning (hopefully before too much damage takes place).

I've also been told by a reliable marine mechanic that running for a minute or so from cold wont harm the engine, i did a very silly thing last year just after i'd had my complete bottom end rebuilt, after comming back from one of my many running in sessions i ran my engine up on the muffs as normal to flush it and normally i stand and watch the water comming out until i'm happy its been suficently flushed through only this time i decided it was ok and walked into the garage for something, when i came back out i notice no water comming out the tel tall and just smoke, alarmed i quickly shut the engine down and inspected the muff only to find the hose had popped off the muff, horrified i quickly re attached the hose and ran some water in before restarting the engine, i then let it run for 15 minutes on the hose feeling the head to make sure it was not getting hot before i was happy i'd not done any damage, crapping myself i went back to my mechanic who told me so long as it was no longer than about a minute then i shouldn't have done any damage

I've had no problems and now the hose is secured to the muff with a jubilee clip, now i'd not suggest running an engine without cooling water going through to anyone and its something i wont be repeating again real soon.

Rat

Nick Hearne · 20 April 2004, 14:56

Ok so I should have been more precise I believe it is the impeller, which will burn out in 5 seconds! But having said that the engine will be getting hot very quickly with out any water cooling it.
Nick

Bilge Rat · 20 April 2004, 15:55

As i previously stated i ran my engine with no cooling going through for about a minute easilly and its done no damage to the engine or impellor, the impellor was changed last summer though, i would have thought i'd have wrecked my engine but its running ok and has done a lot of hours since with no problems and the impellor seems to be fine..... !

I dont recommend repeating this either !!

Daniel TD5 · 20 April 2004, 16:07

as i pick up my new boat friday and my choice of engine is the 40hp mariner
what you are saying is a bit worring to me as i though water should come out
the tell tail all the time. but if you wait for the engine to warm up and no water is coming out will the engine still be cooling when running. or should water come out when going along. and how would you know you have a problem

Mike B · 20 April 2004, 16:23

Daniel,

I'll be very interested to here other peoples views on this one.

IMO after a bit of time you wil get to know your engine.

As I said earlier with my Suzuki if I got worried every time the tell tale stopped I'd be continuously on edge.

If you have a reasonably consistent tell tale and it suddenly stops then this is the time to do some checking.

However if like mine and perhaps some others it regularly stops you need to re think your plan. I try my best to keep the tell tale clear (not very successfully), I try to keep an eye on the water exhaust and check that over a period of time water is expelled indicating that there is water in the system. As a last resort, on my engine, if it over heats an indicator lights on the console, a buzzer sounds and a rev limiter kicks in (it hasn't happen to me yet). At this point I would strongly suggest stopping the engine.

I know this is very vague - but hopefully someone else can fill in any gaps.

Cheers

Mike

Daniel TD5 · 20 April 2004, 16:36

my new boat comes with rev counter but no temp warning as 50hp and above
have trim gauge and rev counter as standard the dealer recommed a rev counter and did not charge me for it. don,t know what temp senders are fitted if any to the 40hp so it could be fitted later. me being new to ribing
though just watch the tell tail if no water we have a problem what happend to make it easy