Signs to watch for if an outboard is overheating (Suzuki 2.2DT)

[FairweatherDave]

My Suzuki has cooling flow, the same as normal. I have checked the impellor and it is fine. Most of the cooling water exits under water but you get a fine spray out of the two little holes on the leg, mainly at idle. So as far as I can see the engine cooling system is fine (I have used this outboard for ten years plus.) I gave the engine a bit of a thrash on Saturday to test how well it was running and maybe some slight fuel starvation occurred as the revs dropped suddenly after a while. The fuel side can be temperamental. However I felt the engine was hotter than I would like, my finger tips on the metal part under the fuel tank were one indicator, and there seemed a fair bit of white exhaust smoke. At the time I did not think "that's steam".
Since then I have run the engine in a bin and observed the normal cooling flow.
So I was thinking of using some rydlyme (I last cleaned the passages manually 3 years ago so I know how they can block up).
But the crunch question is what symptoms should I be looking for so I don't knacker the engine if it is getting too hot?

 

[VicS]

My Suzuki has cooling flow, the same as normal. I have checked the impellor and it is fine. Most of the cooling water exits under water but you get a fine spray out of the two little holes on the leg, mainly at idle. So as far as I can see the engine cooling system is fine (I have used this outboard for ten years plus.) I gave the engine a bit of a thrash on Saturday to test how well it was running and maybe some slight fuel starvation occurred as the revs dropped suddenly after a while. The fuel side can be temperamental. However I felt the engine was hotter than I would like, my finger tips on the metal part under the fuel tank were one indicator, and there seemed a fair bit of white exhaust smoke. At the time I did not think "that's steam".
Since then I have run the engine in a bin and observed the normal cooling flow.
So I was thinking of using some rydlyme (I last cleaned the passages manually 3 years ago so I know how they can block up).
But the crunch question is what symptoms should I be looking for so I don't knacker the engine if it is getting too hot?

In general you should be able to touch and maintain brief finger contact with any part of the cylinder block and head , except for around the spark plug(s) and, where relevant any exposed uncooled exhaust manifold cover .

A splash of water should not boil off

Paintwork should not be showing signs of discoloration and there should not be steam issuing from any of its orifices.

When there is a telltale there should be a good water flow but engines vary in the flow and operation of the telltale . A flow from the telltale usually only indicates that the pup is operating. It does not guarantee a cooling wter flow through the engine.

Am I right in believing that the DT2 does not have a teltale?

 

[FairweatherDave]

Thanks Vic. It does not have a proper tell tale, but a fine spray should be discernible if you put your hand by the two small holes I mention, but the spray is mixed with some exhaust. I am tempted to do the rydlyme anyway as I have not done the passages for three years (but always flush in fresh water a bin after use)..... see if it makes a difference. But I can check your list of signs of overheating as I go along. I might have been paranoid after pushing the engine harder than usual.

 

[alahol2]

My Mariner 2 has the same 'tell tale' system. When mine blocked up the top of the leg, above the tell tale, got very hot and you could not keep your hand on it. I'm fairly sure when it's cooling properly that the top of the leg stays relatively cool.

 

[Seajet]

I have a Mariner 2 and a Mariner 5 - both are 2 strokes.

You should be able to put your hand under the water outlet easily, if it's more than luke warm there's a problem.

As for the Suzuki, source and get a new head gasket then whip the head off; sure as anything the waterways are blocked with salt, I take the heads off my engines at least every other winter.

 

[FairweatherDave]

whip the head off; sure as anything the waterways are blocked with salt, I take the heads off my engines at least every other winter.

Thanks Seajet, I suspect you will be right. I am tempted to try rydlyme first though although I might be wasting just over £10, the cost of the gasket roughly. I did the proper job three years ago and the photos in the link below show how badly things had got blocked up. And to anyone interested, I was religeously flushing in a dustbin. So here are the piks!
https://picasaweb.google.com/DWMacAdam/BlockedCoolingJacket

 

[prv]

You should be able to put your hand under the water outlet easily, if it's more than luke warm there's a problem.

As the OP says, the 2hp Suzuki 2-stroke doesn't have a water outlet as such. It's all dumped into the exhaust and comes out underwater, apart from a very fine spray or mist that escapes from the back-pressure vent holes on the back of the leg.

As for "running harder than usual" - my normal mode of operation with the same engine is to open the throttle to full as soon as we're clear of the boat or jetty, and keep it there until shortly before arrival at the other end. Hasn't done any harm so far

Pete

 

[FairweatherDave]

As for "running harder than usual" - my normal mode of operation with the same engine is to open the throttle to full as soon as we're clear of the boat or jetty, and keep it there until shortly before arrival at the other end. Hasn't done any harm so far

Pete

Blimey!!

 

[DannyB]

As the OP says, the 2hp Suzuki 2-stroke doesn't have a water outlet as such. It's all dumped into the exhaust and comes out underwater, apart from a very fine spray or mist that escapes from the back-pressure vent holes on the back of the leg.

As for "running harder than usual" - my normal mode of operation with the same engine is to open the throttle to full as soon as we're clear of the boat or jetty, and keep it there until shortly before arrival at the other end. Hasn't done any harm so far

Pete

Blimey!!

That's what I do as well, I thought it was normal practice! I might not do the same if it were a 100 HP.

 

[Seajet]

Even with a ' mist spray ' outlet one can put a hand underneath it and feel the flow and temperature, I do this with the Mariner 2hp.

I run my outboards in an oily freshwater fiilled wheelie bin ( what else were they provided for ? ) every autumn and spring, but still every other year- sometimes more often - I take the head off and clear out the waterways.

 

[prv]

Blimey!!

It's a two horsepower motor pushing a ten-foot inflatable - if I didn't run it at max chat I'd never get anywhere

I could be wrong (not really an engine person) but I understood small 2-strokes were generally designed to run best at wide-open throttle. It certainly sounds happiest there.

Pete

 

[ex-Gladys]

It's a two horsepower motor pushing a ten-foot inflatable - if I didn't run it at max chat I'd never get anywhere

I could be wrong (not really an engine person) but I understood small 2-strokes were generally designed to run best at wide-open throttle. It certainly sounds happiest there.

Pete

Yeah, it's great to hear the fuel whizzing down the plug 'ole...

 

[Seajet]

It's a two horsepower motor pushing a ten-foot inflatable - if I didn't run it at max chat I'd never get anywhere

I could be wrong (not really an engine person) but I understood small 2-strokes were generally designed to run best at wide-open throttle. It certainly sounds happiest there.

Pete

I think you're right, though if it hasn't got a clutch, starting it with the throttle wide open may be fast track to an appearance on Youtube - ask how I know ?!

 

[prv]

Yeah, it's great to hear the fuel whizzing down the plug 'ole...

Given that I usually end up wondering what to do with the rest of the 5-litre can I filled up at the start of the season, fuel consumption of the tender is not a major worry for me

Pete

 

[prv]

I think you're right, though if it hasn't got a clutch, starting it with the throttle wide open may be fast track to an appearance on Youtube - ask how I know ?!

I know what you mean - the decrepit 40hp 2-stroke on the Contraption has a bit of a dodgy gearbox, and needs max throttle or thereabouts in order to start. You also need to stand up in order to apply sufficient force to the pull-cord. The boat weighs buggerall, one person can lift it.

Yes, I managed to start it in gear at max throttle. On this occasion I was on my own, so as well as shooting forward the bow also reared up to (seemingly) near-vertical. You only do that once, I can assure you! Genuinely dangerous.

I was at least wearing the kill cord.

Pete

 

[Seajet]

Pete,

at our club the cruisers used to come in bow first to the slipway, so as to be picked up by the mobile crane we hired in, in those days.

Some people used to lay out a kedge astern if they were unsure of slow speed handling.

Meanwhile a hero with a home built dory ( ie pretty much a plywood skip ) with an old huge outboard was haring around being a nuisance...

Close in to the club he whacked the throttle open trying to pose and stalled it - then went to the stern and pulled the recoil chord...it started on first pull and full power, pinning matey helpless headfirst over the engine.

Then the prop picked up someone's kedge line, and it made a Tomcat picking up a carrier arrestor wire look tame, throwing him into the bows.

We thought the least we could do was politely applaud.

 

[FairweatherDave]

I agree that you should be able to run the outboard near full throttle on a perfectly serviced engine. I suspect I don't coz in my overloaded Avon Redstart with low profile tubes and a floppy floor it never seems to go any faster whatever I do. Also I spend most of my time outboarding in very shallow water full of sand particles and my average run to the mooring is just under twenty minutes.I think given the state of my cooling jacket 3 years ago I think I would have cooked the engine if I had. So do the full throttle merchants go for annual use of Rydlyme or a professional service, or do they service their own engines and stay in deeper water most of the time. I'm frequently going up the side of Emsworth channel using an oar as a depth sounder. I'm still undecided whether to try chemicals before the full treatment

 

[prv]

So do the full throttle merchants go for annual use of Rydlyme or a professional service, or do they service their own engines and stay in deeper water most of the time.

The latter really - plus the fact that my home berth is walk-ashore so I don't use the tender much except on cruises to the West Country or Channel Islands.

I dismantled the engine to check it over when I got it; it was pretty clean then, having only been used a few times in freshwater, the reason I chose it. I'll do so again in due course, but probably not for another couple of years. I checked the impeller at the weekend, and it looked like new. I do always give it a flush in the bin after each cruise.

Pete