Mukuni Heating and Hot water advice

[KirstieH]

Hello

 

I think I am about to buy a narrowboat...and have since found out the Heating is "Temperamental" Which prob means it is knackered.

 

It is a Mukuni system and I wondered if anyone had any idea:

 

1) If you could call out an engineer to locate the problem...even if the owner can't suggest what the issue might be...Needle in haystack?

 

2) If it is worth just installing a new system...if so which one and how much are we talking ...GULP

 

Any advice welcomed

[nicknorman]

Mikunis, along with other similar evaporative diesel heaters, are not particularly robust and reliable. Personally I wouldn't want to have that as my only hearing source for live-aboard. We have a Mikuni that we use for "occasional" heat, warming the boat on arrival or on a spring / Autumn morning / evening when it's not worth lighting the coal fire.

 

Things that upset Mikunis are:

 

Sooting up due to "short cycling" ie turning on and off in response to a thermostat. Don't use a thermostat, or TRVs on the radiators! Or just a need for a decoke after a lot of use.

 

Poor lighting up can be due to voltage drop in the wiring. During lighting the glow plug takes a lot of current and substantial wiring is needed to ensure a good voltage supply.

 

I've found our's to be fairly reliable with the exception of the glow plug - we seem to need a new one every year or so - but they are only £25 or so and should be considered a "consumable"

[Biggles]

I had a Mikuni. After a year of noise and increasing unreliability and regular de-coking, I took it out and fitted a Hurricane £2500 as I recall. Never had a problem in 3 years.

[nicknorman]

If a Mikuni needs very regular decoking it's probably because the air:fuel ratio is wrong. This can be adjusted but you need a competent Mikuni expert with gas analyser. Rich mixture probably means it's putting out plenty of CO too.

[KirstieH]

Thanks guys. I wonder if the wool is being pulled over regarding this heater...why would someone not try to have it fixed before selling? Gah its hard work buying a boat!!!

[NMEA]

.why would someone not try to have it fixed before selling? Gah its hard work buying a boat!!!

Maybe they have, without success. Problem is that there are plenty of people who say they can sort them but beyond a decoke or simple wiring issue do dot have the equipment or experience. There are many other considerations. Not the least of which is the CO & CO2 (burn rate) is quite complex to do on the Miki water heaters as it involves careful shimming and is really a workshop job. On the other hand it may be something simple like corroded terminals or cable, glow plug boss burned (quite common). The other part of the equation of course is that the boiler is only one part of the system and that needs to be right too. Temperamental is quite nebulous fault description so you really need to know the precise symptoms before further comment, poor starting? low heat output? flame outs? excess noise (exhaust excepted). Correctly installed, properly looked after and used for the purpose for which they are intended they will give many years of service but incorrectly used, ignored, or subjected to uninformed tampering they will complain bitterly. Consider also that parts are becoming increasingly difficult since Mikuni stopped production, I have two heaters in my workshop that I have been awaiting parts on for some time with still no sign of a delivery date.

Edited May 17, 2016 by NMEA

[KirstieH]

Maybe they have, without success. Problem is that there are plenty of people who say they can sort them but beyond a decoke or simple wiring issue do dot have the equipment or experience. There are many other considerations. Not the least of which is the CO & CO2 (burn rate) is quite complex to do on the Miki water heaters as it involves careful shimming and is really a workshop job. On the other hand it may be something simple like corroded terminals or cable, glow plug boss burned (quite common). The other part of the equation of course is that the boiler is only one part of the system and that needs to be right too. Temperamental is quite nebulous fault description so you really need to know the precise symptoms before further comment, poor starting? low heat output? flame outs? excess noise (exhaust excepted). Correctly installed, properly looked after and used for the purpose for which they are intended they will give many years of service but incorrectly used, ignored, or subjected to uninformed tampering they will complain bitterly. Consider also that parts are becoming increasingly difficult since Mikuni stopped production, I have two heaters in my workshop that I have been awaiting parts on for some time with still no sign of a delivery date.

This was a very useful post and has made me think a new one is probably on the cards which we can look after from scratch.....my worry is, what else will need doing as a result ( How far do these issue go

[NMEA]

If it is a Miki MX40 there is an exchange direct replacement available which is simply a case of unbolting the old one and replacing with the more modern "plug and play" unit. Assuming the rest of the system is OK, 22mm distribution tubes used, enough rads to load the heater, no TRVs etc. then all that should be needed is a good flush out of the system before refitting. Don't despair though as the Mikuni may well be recoverable and the very least you have is a good negotiating point, Assuming the boat is what you want otherwise and the survey comes out well don't let this relatively minor issue put you off.

[DustyDave]

Same thing happened to me when I was buying a boat. Fresh set of batteries did the job. When used occasionally I still had reliability issues but when used daily it was great. Still could have done with a wood burner for the winter.

 

Dave

[KJT]

I had a Mikuni. After a year of noise and increasing unreliability and regular de-coking, I took it out and fitted a Hurricane £2500 as I recall. Never had a problem in 3 years.

Our boat had a Mikuni fitted when new, about 14 years ago. It only lasted six months and was taken out and replaced with a Hurricane. Faultless reliability for the last 13 years or so. And a simple 1000 hour/annual service. I highly recommend the Hurricane.

 

Ken