Problems & solutions mb2a50s

[Howard]

Impeller damage to engines - change each year - check water output!

The most common problem is poor maintenance of these very reliable engines. The impeller does need to be changed every season or problems do occur. The main issues is that although the engine seems to run well it will run too hot and at high loads white smoke can be seen. This is steam and if you put your hand (careful very hot!) on the little water coming out you will see it is close to boiling point. This results in a quick build up of residue in all the waterways within the engine. It will not typically activate the overheat sensor as the sensor will only operate if water circulation has stopped completely for some time. I have seen many engines with water ways completely blocked and even one I have in the workshop where the cylinder jacket has burst! Even this is being repaired. (We really are adamant about keeping these engines in service for many years).

Check the water output at high load if you are in any doubt about the state of your impeller. If you have seen white smoke you can do one of two things. The first is replace the impeller (and inspect the gearbox leg & service while you can) then you could use a radiator flush type liquid. I do not recommend this as by using the wrong type you could cause damage but I do know a number of people that have been successful in this approach. I believe that you should bit the bullet and strip down the cylinder head as I don't think you will be able to clear all the waterways and long term damage will result. Its not a very long job about 4 hours but it give you the chance to check many important parts at the same time. Yes I could also service the head or provide an exchange unit.

[Howard]

Alarms not working overheat & oil pressure

Yes, test them regular and replace the blue electronics box.

With the engine running you can test the oil pressure sensor by connecting the sensor to the engine block. The alarm should sound loud!! and the light should come on.

This test most on the electrics but the sensor was not tested. The common problem is not the sensor though and this can be tested with a test lamp or meter the sensor is just a switch.

The overheat sensor can be test in the same way and is also just a switch.

In most cases the alarms do not work CHECK yours now or risk a very expensive repair and no sailing. If its happened then we can supply exchange engines!

If your alarms don't work then you will probably need an exchange blue box & a new Alarm sounder. I am looking at making these available soon but if you need help I can supply / exchange now.

[Ian]

Howard, is exhaust steam (white smoke) a sign of running too hot? I have visible steam from cold start to full hot and assumed this was normal evaporation of the cooling water into the exhaust. Waterways are clear, I have a new thermostat and there is a good flow of water in the exhaust.

Ian

Howard Wrote:Impeller damage to engines - change each year - check water output!

The most common problem is poor maintenance of these very reliable engines. The impeller does need to be changed every season or problems do occur. The main issues is that although the engine seems to run well it will run too hot and at high loads white smoke can be seen. This is steam and if you put your hand (careful very hot!) on the little water coming out you will see it is close to boiling point. This results in a quick build up of residue in all the waterways within the engine. It will not typically activate the overheat sensor as the sensor will only operate if water circulation has stopped completely for some time. I have seen many engines with water ways completely blocked and even one I have in the workshop where the cylinder jacket has burst! Even this is being repaired. (We really are adamant about keeping these engines in service for many years).

Check the water output at high load if you are in any doubt about the state of your impeller. If you have seen white smoke you can do one of two things. The first is replace the impeller (and inspect the gearbox leg & service while you can) then you could use a radiator flush type liquid. I do not recommend this as by using the wrong type you could cause damage but I do know a number of people that have been successful in this approach. I believe that you should bit the bullet and strip down the cylinder head as I don't think you will be able to clear all the waterways and long term damage will result. Its not a very long job about 4 hours but it give you the chance to check many important parts at the same time. Yes I could also service the head or provide an exchange unit.

[Howard]

I would be very careful the white steam does normaly mean that your engine is running to hot and this will build up contamination in your waterways (at least). If as you say the water ways are clear (incvulding the block, all pipes & water sea cock) then I would think that either your impeller is at fault or perhaps some other restriction in the cooling system has occured. The pipe that conects both ends of the sail drive leg can become hard & leaky & of course the pump bottom plate can be worn or strainer can get restricked. But if you have white smoke (steam, you are running to hot & I would investigate with zest). Are you sure your alarms are working?




Howard, is exhaust steam (white smoke) a sign of running too hot? I have visible steam from cold start to full hot and assumed this was normal evaporation of the cooling water into the exhaust. Waterways are clear, I have a new thermostat and there is a good flow of water in the exhaust.

Ian

Howard Wrote:Impeller damage to engines - change each year - check water output!

The most common problem is poor maintenance of these very reliable engines. The impeller does need to be changed every season or problems do occur. The main issues is that although the engine seems to run well it will run too hot and at high loads white smoke can be seen. This is steam and if you put your hand (careful very hot!) on the little water coming out you will see it is close to boiling point. This results in a quick build up of residue in all the waterways within the engine. It will not typically activate the overheat sensor as the sensor will only operate if water circulation has stopped completely for some time. I have seen many engines with water ways completely blocked and even one I have in the workshop where the cylinder jacket has burst! Even this is being repaired. (We really are adamant about keeping these engines in service for many years).

Check the water output at high load if you are in any doubt about the state of your impeller. If you have seen white smoke you can do one of two things. The first is replace the impeller (and inspect the gearbox leg & service while you can) then you could use a radiator flush type liquid. I do not recommend this as by using the wrong type you could cause damage but I do know a number of people that have been successful in this approach. I believe that you should bit the bullet and strip down the cylinder head as I don't think you will be able to clear all the waterways and long term damage will result. Its not a very long job about 4 hours but it give you the chance to check many important parts at the same time. Yes I could also service the head or provide an exchange unit.

[/quote]

[Ian]

Thanks Howard - I installed a new impeller this spring and have good water flow. I'll bring a thermometer out next week and check the actual discharge water temp and the operation of the alarms.
Ian

Howard Wrote:I would be very careful the white steam does normaly mean that your engine is running to hot and this will build up contamination in your waterways (at least). If as you say the water ways are clear (incvulding the block, all pipes & water sea cock) then I would think that either your impeller is at fault or perhaps some other restriction in the cooling system has occured. The pipe that conects both ends of the sail drive leg can become hard & leaky & of course the pump bottom plate can be worn or strainer can get restricked. But if you have white smoke (steam, you are running to hot & I would investigate with zest). Are you sure your alarms are working?




Howard, is exhaust steam (white smoke) a sign of running too hot? I have visible steam from cold start to full hot and assumed this was normal evaporation of the cooling water into the exhaust. Waterways are clear, I have a new thermostat and there is a good flow of water in the exhaust.

Ian

Howard Wrote:Impeller damage to engines - change each year - check water output!

The most common problem is poor maintenance of these very reliable engines. The impeller does need to be changed every season or problems do occur. The main issues is that although the engine seems to run well it will run too hot and at high loads white smoke can be seen. This is steam and if you put your hand (careful very hot!) on the little water coming out you will see it is close to boiling point. This results in a quick build up of residue in all the waterways within the engine. It will not typically activate the overheat sensor as the sensor will only operate if water circulation has stopped completely for some time. I have seen many engines with water ways completely blocked and even one I have in the workshop where the cylinder jacket has burst! Even this is being repaired. (We really are adamant about keeping these engines in service for many years).

Check the water output at high load if you are in any doubt about the state of your impeller. If you have seen white smoke you can do one of two things. The first is replace the impeller (and inspect the gearbox leg & service while you can) then you could use a radiator flush type liquid. I do not recommend this as by using the wrong type you could cause damage but I do know a number of people that have been successful in this approach. I believe that you should bit the bullet and strip down the cylinder head as I don't think you will be able to clear all the waterways and long term damage will result. Its not a very long job about 4 hours but it give you the chance to check many important parts at the same time. Yes I could also service the head or provide an exchange unit.

[/quote]

[Ciao Bye]

Hi Ian,

You are writing: I installed a new impeller this spring and have good water flow.

Mine has not a constant flow of water at idle even at medium rpm. It is spitting water, white smoke and the rubber exhaust hose get very warm. The alarm are working normally. I looked at the boat with diesel engine and the water is wunning most of the time. When I am running it at allmost full rpm the exhaust end is in the water so I cannot say anything at this rpm range.

Could you be more precise on how the water actually goes out so I could compare with mine. Too bad we cannot post a video so we could compare much easyly.

Thanks

John


[quote=Ian]
Thanks Howard - I'll bring a thermometer out next week and check the actual discharge water temp and the operation of the alarms.
Ian

[Ian]

John, it spits water out when the level in the exhaust box gets high enough, then there's no water for maybe five to ten seconds, then another slug comes out. I think that's normal. It's hard to imagine any more water could flow through the 1/4" cooling water tubing these motors use.

Diesels I have seen do the same except not as much water vapor condensing, and also more water flow - but those engines are usually three times the size. Maybe there is more water vapour with these small gas engine because the exhaust gas runs hotter.

The thermostat full open temp is 158 degF and the exhaust would be even hotter so the exhaust hose will definitely become too hot to hold your hand on, but that doesn't mean there is a problem.

I'll post again after I measure the water temp at the exhaust next week.

Ian

Ciao Bye Wrote:Hi Ian,

You are writing: I installed a new impeller this spring and have good water flow.

Mine has not a constant flow of water at idle even at medium rpm. It is spitting water, white smoke and the rubber exhaust hose get very warm. The alarm are working normally. I looked at the boat with diesel engine and the water is wunning most of the time. When I am running it at allmost full rpm the exhaust end is in the water so I cannot say anything at this rpm range.

Could you be more precise on how the water actually goes out so I could compare with mine. Too bad we cannot post a video so we could compare much easyly.

Thanks

John


[quote=Ian]
Thanks Howard - I'll bring a thermometer out next week and check the actual discharge water temp and the operation of the alarms.
Ian

[Ciao Bye]

Thanks alot Ian.

Mine does exactly the same thing. I am more relax now that I've read your explanation.

Take care

John

[quote=Ian]
John, it spits water out when the level in the exhaust box gets high enough, then there's no water for maybe five to ten seconds, then another slug comes out. I think that's normal. It's hard to imagine any more water could flow through the 1/4" cooling water tubing these motors use.

[HarryS]

I ran into an engine alarm this weekend. It appeared after a 30min drive with 3/4 trottle. It seems to be a problem with the engine getting too hot at higher trottle. As it seems to be a pain getting to the impeller (I need to get the ship out of the water - right?) I disassembled and checked the thermostat first.

Removing the water lines just behind the closing valve shows a constant water flow with the engine ideling, it has not a lot of pressure, however. Having nothing to compare, I'm not sure if this is normal or should be more.

The thermostat moves only 1-2mm between cold and nearly boiling water. Furthermore it is (very) open at any heat. I think it should be closed when the motor is cold?

I have white smoke, sometimes less, sometimes more.

Your oppinion?

Harald

[Howard]

Harry, yes to change the impeller is quite a big job but not if you can do it once a year when the boat comes out for the winter.

The Thermostat - at 70 degrees you should be able to measure 3 to 4 mm and 0 at 60 degrees. The complete picture can be found at page 11 in the manual on the home page of this site.

My opinion is that you probably have a faulty thermostat but I would not be surprised if your impeller was at fault as well. Did you change it last year? The water ways do get quite blocked throughout the engine including the seacock (the water tap) and I would suggest that you check they are all clear the next time you can. But if you change the faulty thermostat and the engine runs well at full throttle then I would be happy to leave everything else to the winter checks.



Howard

HarryS Wrote:I ran into an engine alarm this weekend. It appeared after a 30min drive with 3/4 trottle. It seems to be a problem with the engine getting too hot at higher trottle. As it seems to be a pain getting to the impeller (I need to get the ship out of the water - right?) I disassembled and checked the thermostat first.

Removing the water lines just behind the closing valve shows a constant water flow with the engine ideling, it has not a lot of pressure, however. Having nothing to compare, I'm not sure if this is normal or should be more.

The thermostat moves only 1-2mm between cold and nearly boiling water. Furthermore it is (very) open at any heat. I think it should be closed when the motor is cold?

I have white smoke, sometimes less, sometimes more.

Your oppinion?

Harald

[HarryS]

Thanks Howard. Both the termostat and the impeller were defect. I changed the termostat first, but ran into the temperature alarm again. I had to take the boat out of the water and changed the impeller. It was not only damaged, but rubber parts of the impeller blocked the water way upwards... A big mess... After changing the impeller, everything is running fine. I bought the ship (including the motor) beginning of this year and did not do the necessary maintenance steps... Sometimes you have to pay for learning ;-)

By the way - and reading trough the whole thread again - the exhaust shows a lot less white smoke now. The motor and the exhaust were obviously too hot.

Harald

[Howard]

Harald

Yes, I agree but its good that your engine is now in sound condition and that you are sure your alarms are working. Perhaps a more accurate temperature indicating system could be of use to warn of a defective cooling system. I will try to look into it over the winter months.

[Ciao Bye]

I have to change my impeller after each season. I am doing it right now and will soon be running out of them

They get bend a lot and the fin on the impeller break. I only put 12 hours on the engine ths summer.

Can we blow air into the engine to make sure the passage are free of debris without breaking anything with compress air ????

Thanks a lot.

John
Quebec
Canada

[Howard]

John

I don’t know if compressed air is a good idea the contamination that I have found inside the waterways will not be removed in my opinion. I am surprised if you only had 12 hours use between impeller changes. It could be that your water pump housing is damaged. I have seen this before; the impellers should last many hundreds or even thousands of hours. Many users have used the same impeller for years before changing them. I do have to say at this point that this has sometimes been the reason for engine damage and the cooling system has at times become inefficient as the impellers failed. The impellers can also become quickly damaged if run without water, could this have occurred? Are you sure the Impellers are from a known good source and that they are the right component? Hope this helps,


Howard

[Ciao Bye]

Hi.

The impeller has a crack in one of the blade. The inside of the water pump housing seems to me to be in perfect condition when I compared it with my other engine (I have 2)

In no way the impeller has been run without water. The quality of the impeller must be at fault. I have bought 2 of them from a company in the USA. Maybe the rubber had been standing in the shelf for too long.

Do you have brand new one? how old are they? How much they cost if you ship them in Canada?

I finally have found some rubber engine mount, I got them from my old engine. The are in good condition as far as I can see. I will try to make 2 limiter for them with a cold rod as I saw in your pictures. If I cannot succeed in doing so, I will order them with you.

As for not blowing air into the engine, it was only a suggestion to see if air is passing trought the inlet, but I doubt that they are blocked since water is pouring at the exaust.

Thanks again and keep that superb forum alive. You are a great help to all of us.

John
Quebec
Canada