Mariner 25hp 2 Stroke interesting Tell Tail

[smallribber]

This rather nice outboard became available at my local shop and it was just what we wanted as a second motor for the Honwave T40 AE3. Plus I like buying outboards . It seems in very good condition but when I first saw it test run I was concerned about its cooling. It turns out this is how this particular outboard was designed. Very disconcerting if you are not aware.

Little video below that explains how this one works.

Hopefully this will push the T40 along nicely and for £1,080 I could not resist

https://www.youtube.com/watch?v=kihOFzrmU4c

[Steve509926]

So what happens if the impeller fails when you first fire it up? As there is no initial tell tail until the thermostat opens you wouldn't know until .......... Or is there another indicator that shows the impeller is working?

[User name]

I worked on one of these and it would pump from cold, but much stronger when hot. Are you sure yours working right?

[smallribber]

Originally Posted by User name

I worked on one of these and it would pump from cold, but much stronger when hot. Are you sure yours working right?

Yup it contacted the technical guy at Mariner and he confirmed this is how it is designed to work.

I suppose there could be a small bypass hole that could be blocked for a show when cold. But to be honest this would serve little purpose because I would most likely not set off before I did see water which is about 30 - 40 seconds.

I recall Donny never sets off till his engine is warm. This might have been why

[smallribber]

Originally Posted by Steve509926

So what happens if the impeller fails when you first fire it up? As there is no initial tell tail until the thermostat opens you wouldn't know until .......... Or is there another indicator that shows the impeller is working?

No idea but on the other hand this is in some ways a double tell tail. ie when it shows water it tells you that it is pumping and also that the thermostat is working.

My other outboards only tell you that the pump is working but the stat might not be working. This is a very bad situation once up the river.

On this one if you start it and by the time you were ready for the off etc it should be peeing. If it isnt then probably an issue.

In the shortish time it takes to open the stat no damage to the outboard would be done.

I understand that these were made with this arrangement and also the normal arrangement but not certain on that one.

I found this very interesting to be honest

[Fenlander]

As mentioned before I've owned three of this same make/coolant system and they were all intermittent dribbles at idle when cold as they should be but would pump well when faster, even at just a raised idle.

It's something I've warned folks of when they mention they are going to view a Mercury/Mariner 10 or 15hp.

However I'm surprised you were surprised as you've owned a Mercury 15 for years that has the same system and should behave the same... unless the stat is faulty or missing.

[The Gurnard]

Hi Dennis..your outboard looks very much like my old one. Have you taken the thermostat housing cover off ?

If so does it look like my old one under the housing .(see photo)




Mine had a bypass hole so it splutters water when started although I agree it doesn't flow fully until the thermostat opens.

Just mentioning in case others think their outboard is fine if its not spluttering when started.. however yours may be different from mine.

I think the RNLI ones were altered to run much cooler but their tell tale outlet was moved away from the thermostat housing so neither of ours are / were ex RNLI models.

Im no expert though ..your may not have a bypass hole but I suspect it has and you just don't know it?

Yours may not be spluttering cos you are using muffs ..I always did mine in a bucket ..so try that and see if it splutters when started.

If it has a bypass hole and not spluttering when started in a bucket ..worth looking into why its not spluttering instead of thinking its normal

I should have added..that the impeller housing needs to be under water when starting in a bucket too.. as its not the best self primer. I burned the tips of several impellers because the water was only up to the anti cavitation plate when starting after changing the impeller, and the housing was dry. So be aware it doesn't take long to burn an impellers blades if its dry.

[Fenlander]

>>If it has a bypass hole and not spluttering when started in a bucket ..worth looking into why its not spluttering instead of thinking its normal

Hi Donny you are thinking along the same lines as myself as I don't remember ever seeing no water or so little water on the related models. But like you I never use muffs.

Did they put a new impeller in at the point of sale I wonder?

[The Gurnard]

Originally Posted by Fenlander

>>If it has a bypass hole and not spluttering when started in a bucket ..worth looking into why its not spluttering instead of thinking its normal

Hi Donny you are thinking along the same lines as myself as I don't remember ever seeing no water or so little water on the related models. But like you I never use muffs.

Did they put a new impeller in at the point of sale I wonder?

I suspect it could be muff running and not a bucket Fenlander ?.

I only posted as I got the impression Dennis was saying its normal for a Mariner 25HP 2 stroke not to splutter when started.. that was certainly not normal for mine.. it spluttered as soon as it started. Im sure your did too..that is why the bypass hole is there. Hopefully Dennis will confirm what is under his thermostat housing and if it has a bypass hole mention that so its accurate info he is posting

[The Gurnard]

I forgot about this video..I do a cold start of my Mariner 25Hp 2 stroke at 11 mins 15 seconds in. After the outboard fires..it takes about 2 seconds for the waterpump to get the water round the cooling passages and out the pee hole ..you then clearly see the spluttering water.. wait a minute or so and the thermostat opens and the flow begins. Hope that clarifies things ..for my old Mariner 25HP 2 stroke anyhoo.

https://www.youtube.com/watch?v=wiRhm5OIDPc&t=672s

Dennis as an afterthought.. when you remove the thermostat cover ..check the gasket has the hole alined with the bypass hole..if its on the wrong way..the gasket will block the hole and that could be an issue too

[smallribber]

Many thanks for the useful words. When I bought it from Seamark Nunn they put it in their very large tank with. Now I think about it it was indeed spluttering cos I remember pushing a piece of strimmer wire up its chuff to try and clear it. I suspect I have the same one as Donny had. I will do a little test in a tub when I get a chance.

Either way I am quite pleased with the old thing.

[smallribber]

Originally Posted by Fenlander

As mentioned before I've owned three of this same

However I'm surprised you were surprised as you've owned a Mercury 15 for years that has the same system and should behave the same... unless the stat is faulty or missing.

I have indeed got one of those and I have not used it in ages. I never checked but I suspect it had the thermostat removed.

[smallribber]

Originally Posted by The Gurnard

Dennis as an afterthought.. when you remove the thermostat cover ..check the gasket has the hole alined with the bypass hole..if its on the wrong way..the gasket will block the hole and that could be an issue too

I certainly will check. I looked at the size of the T40 the other day and felt it would be ideal to convert into a mini cabin cruiser like some mad chap has done

[The Gurnard]

The T40 is a great outfit Dennis.

I recall going round Mull with Highland Haggis and his mate. He had a 20HP EFI tohatsu 4 stroke on his and two up.. his outfit was faster than me in my Quicksilver one up and my 25HP 2 stroke.

I know you like two strokes but are you aware the Yamaha 25HP EFI 4 stroke is only 3kg heavier, Goes just as fast as the old two 25hp stroke..uses almost 1/3rd less fuel on long trips.. does the same cruising speed of 16knots at a third of the throttle while the two stroke was reving its guts out at two thirds its throttle ..so very much noisier. The two stroke fumigated folks following me on SIB outings.

The only advantage of the two stroke was it accelerated a bit faster..but as I never open the throttle full it meant nothing to me as Im not a racer.

Servicing ? Well I have had the 25HP EFI three seasons now and still only change oil, spark plugs and impeller plus an oil filter .. so..so far little difference

Im sure you will recall telling me to get a drone as they were great things. I always resisted as I didn't believe you ..but eventually I got one..and I admit .. you were correct..it is a great thing.

Why am I mentioning this ?

Well if you got yourself a decent EFI fourstroke to replace that heavy old two stroke..you might change your mind too. You need a trailer for that outfit .. so it doesn't have the advantage of a 15HP or smaller two stroke ..

only my thoughts based on my experience though ..so take it with a wee dram of two stroke oil if you wish

[smallribber]

Originally Posted by The Gurnard

The T40 is a great outfit Dennis.

I recall going round Mull with Highland Haggis and his mate. He had a 20HP EFI tohatsu 4 stroke on his and two up.. his outfit was faster than me in my Quicksilver one up and my 25HP 2 stroke.

I know you like two strokes but are you aware the Yamaha 25HP EFI 4 stroke is only 3kg heavier, Goes just as fast as the old two 25hp stroke..uses almost 1/3rd less fuel on long trips.. does the same cruising speed of 16knots at a third of the throttle while the two stroke was reving its guts out at two thirds its throttle ..so very much noisier. The two stroke fumigated folks following me on SIB outings.

The only advantage of the two stroke was it accelerated a bit faster..but as I never open the throttle full it meant nothing to me as Im not a racer.

Servicing ? Well I have had the 25HP EFI three seasons now and still only change oil, spark plugs and impeller plus an oil filter .. so..so far little difference

Im sure you will recall telling me to get a drone as they were great things. I always resisted as I didn't believe you ..but eventually I got one..and I admit .. you were correct..it is a great thing.

Why am I mentioning this ?

Well if you got yourself a decent EFI fourstroke to replace that heavy old two stroke..you might change your mind too. You need a trailer for that outfit .. so it doesn't have the advantage of a 15HP or smaller two stroke ..

only my thoughts based on my experience though ..so take it with a wee dram of two stroke oil if you wish

Donny

Always wise words from you as ever. I actually have a Mercury 4 stroke 20 hp on the Honwave T40 at the moment and that will be my main engine on it. It is actually the carb version but is certainly very quiet and fuel efficient. I only bought the 25hp 2 stroke on a Whim (I do that a lot ) to give it a go from time to time. I am rather weird and like outboard Motors. I have lost accurate count but have about 14 of them from 200hp V6 to a 2.5hp and even an old Seagull that I bought just to own one. I may indeed get a 25 Yam but that will be a little later

[User name]

Originally Posted by The Gurnard

I forgot about this video..I do a cold start of my Mariner 25Hp 2 stroke at 11 mins 15 seconds in. After the outboard fires..it takes about 2 seconds for the waterpump to get the water round the cooling passages and out the pee hole ..you then clearly see the spluttering water.. wait a minute or so and the thermostat opens and the flow begins. Hope that clarifies things ..for my old Mariner 25HP 2 stroke anyhoo.

Dennis as an afterthought.. when you remove the thermostat cover ..check the gasket has the hole alined with the bypass hole..if its on the wrong way..the gasket will block the hole and that could be an issue too

Great video. The one I worked on spluttered exactly like yours did in the video there. My suspicion would be the bypass too. Someone probably put the wrong gasket on, or put the right one in upside-down.