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  1. #1
    Join Date
    Apr 2019
    Posts
    14

    Default Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Hi all, Iím new to the forum and to forums in general so apologies for mistakes and if posted in the wrong place, I posted it here because the boat is kept at Barry island.

    I know itís been covered but just looking for advice with regard my exact scenario and weather it would seem pointless to carry on with my current approach.

    Iíve recently purchased a new to me westerly centaur with an aged Penta MD2B which starts first turn of the key and seems to be a good engine over all. Unfortunately however I recently ran it for an extended period of time for the first time after changing the impeller and thermostat (as a precaution) and the cylinders are overheating canít even touch them they got so hot.

    Thereís a good flow of water out the exhaust however I presume the coolant passages round the engine were so blocked no water was going round the block.

    Iíve Taken the exhaust manifold off and poked about with coat hanger wire, then directly injected bicarbonate and vinegar (gentle approach), then holts speed flush from Halfords, then oxilic acid and let it sit overnight. I injected this with a syringe straight into the ports on the side of the block after removing the exhaust manifold . The result is the rear cylinder now runs cool as it should, but the forward one still runs hot.

    I have been advised to try brick cleaner which is a bit stronger and intend to do this as the next step. Failing that is there anything else I can do without removing the head ?

    If it comes to having to remove the head I would be looking for a mechanic to do it for me I think as I am not too confident about that step and also in a rush to get the boat in the water.

    Any help is much appreciated.

    Sorry for the essay I struggle to be concise

    May be embarrassing if I have posted this in the wrong place

    Cheers, Andy

  2. #2
    Join Date
    Jul 2002
    Location
    Home: Kent. Boat: Chichester
    Posts
    43,072

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Quote Originally Posted by Andy92 View Post
    Hi all, I’m new to the forum and to forums in general so apologies for mistakes and if posted in the wrong place, I posted it here because the boat is kept at Barry island.

    I know it’s been covered but just looking for advice with regard my exact scenario and weather it would seem pointless to carry on with my current approach.

    I’ve recently purchased a new to me westerly centaur with an aged Penta MD2B which starts first turn of the key and seems to be a good engine over all. Unfortunately however I recently ran it for an extended period of time for the first time after changing the impeller and thermostat (as a precaution) and the cylinders are overheating can’t even touch them they got so hot.

    There’s a good flow of water out the exhaust however I presume the coolant passages round the engine were so blocked no water was going round the block.

    I’ve Taken the exhaust manifold off and poked about with coat hanger wire, then directly injected bicarbonate and vinegar (gentle approach), then holts speed flush from Halfords, then oxilic acid and let it sit overnight. I injected this with a syringe straight into the ports on the side of the block after removing the exhaust manifold . The result is the rear cylinder now runs cool as it should, but the forward one still runs hot.

    I have been advised to try brick cleaner which is a bit stronger and intend to do this as the next step. Failing that is there anything else I can do without removing the head ?

    If it comes to having to remove the head I would be looking for a mechanic to do it for me I think as I am not too confident about that step and also in a rush to get the boat in the water.

    Any help is much appreciated.

    Sorry for the essay I struggle to be concise

    May be embarrassing if I have posted this in the wrong place

    Cheers,
    Andy
    The PBO Reader to Reader forum would have been the most sensible place. Your problem is not unique to the Bristol Channel and Reader to Reader is the place for all practical advice.

    Dont duplicate your post though.... Ask the moderators to move your post or perhaps put a short post there with a link to this one.

    I think you are on the right track . Are you sure you got all the channels in the manifold clear ?

    Those old raw water cooled VP engines are a real pain when it comes to getting the water ways clear ( we had trouble with a MD11C 20 or so years ago.. and the MD2B is its predecessor. Its over 40 years old.

    A sulfamic acid based central heating descaler such as Fernox DS 3 would be my choice for a less aggressive chemical than a hydrochloric acid based brick cleaner, or alternatively Rydlyme. To be effective though any acid cleaner needs to be circulated ( and with the milder ones also warmed ) If there is absolutely no circulation due to complete blockage of parts then you are fighting a loosing battle.

    Heads off and blocks lifted off may be the only way. ( You do need the right type of piston ring compressor though to refit the blocks!)
    Last edited by VicS; 22-04-19 at 13:42.

  3. #3
    Join Date
    Nov 2001
    Location
    scotland
    Posts
    3,290

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Quote Originally Posted by VicS View Post
    The PBO Reader to Reader forum would have been the most sensible place. Your problem is not unique to the Bristol Channel and Reader to Reader is the place for all practical advice.

    Dont duplicate your post though.... Ask the moderators to move your post or perhaps put a short post there with a link to this one.

    I think you are on the right track . Are you sure you got all the channels in the manifold clear ?

    Those old raw water cooled VP engines are a real pain when it comes to getting the water ways clear ( we had trouble with a MD11C 20 or so years ago.. and the MD2B is its predecessor. Its over 40 years old.

    A sulfamic acid based central heating descaler such as Fernox DS 3 would be my choice for a less aggressive chemical than a hydrochloric acid based brick cleaner, or alternatively Rydlyme. To be effective though any acid cleaner needs to be circulated ( and with the milder ones also warmed ) If there is absolutely no circulation due to complete blockage of parts then you are fighting a loosing battle.

    Heads off and blocks lifted off may be the only way. ( You do need the right type of piston ring compressor though to refit the blocks!)
    Ideally you should be able to get a flow of water out the drain plugs and BE CAREFUL The gaskets under the blocks are actually shims and determine the bump height

  4. #4
    Join Date
    Apr 2019
    Posts
    14

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Hi VicS,

    Thanks for the reply, I will do that, do I just copy the link from the browser and start a new post under the same name with the link pasted into it ?

    The manifold is completely clear I think itís quite a bit newer than the rest of the block as well, there is some sea-life growth near the thermostat housing end that the oxilic didnít shift overnight but itís wide open there so Iím not too worried, the small ports were blocked originally but now have good flow through them.

    I will try persisting in a similar manner for a while if it isnít totally hopeless then.

    I will try the fernox first, Iím concerned as inevitably try as i might these chemicals seem to end up in the bilge and I have to swill it out fast so weaker is definitely better for me.

    The circulation is good now Iíve prodded but not enough volume going in so must be well blocked round the cylinder, difficult to rig up anything that isnít messy because the ports in the side of the block (under the manifold) arenít tapped and I was worried about circulating it through the entire engine because then I think it will bi pass the localised problem ? Maybe a constant feed in the top and catch it in a bucket then repeat for hours and hours haha

    Brick cleaner will be a last resort before the head I reckon.

    May be out of my depth taking the head off, never done that before, suppose thereís only one way to learn !!

    There was an unused crated engine on eBay recently for 2000 which I wasnít financially ready to do at the time but now Iím wondering if that was a mistake and I should have bitten the bullet.

    Thanks again for your advice itís nice to know Iím on the right track

  5. #5
    Join Date
    Apr 2019
    Posts
    14

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Hi Scottie thanks for the reply,

    Maybe Iím getting there I get a gush from the rear drain now where before it didnít flow at all and the forward drain is an enthusiastic dribble !!

    Do I have to be careful if I have to remove the head ? Is it easy to get a gasket thatís shimmed the same ?

    Thanks for the help

  6. #6
    Join Date
    Aug 2016
    Location
    Bristol
    Posts
    263

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Our ~35 year old VP ran a little too hot after extended peroids when we first bought her, to the extent we couldn't go faster than 8mph (depressing when planing speed is 15mph).

    I don't know if any of this will be relevant to your model, but hey, I'll ramble on ...

    We tried a few things, as below. Sheepishly, I suspect #1 was the resolution.

    1. Top up coolant.
    Our engine manual specified filling up to a certain point visible through the nozzle. Instead we filled up to the overflow and would just clean up the overspill.

    2. Replaced water pump.
    Our water pump leaked a bit. We'd have to clean an inch of water out of the bilge per hour of use. Engineer reckoned there wasn't any point changing the seals given its age and the unlikeliness of success. So we replaced it.

    3. Clean filter.
    Probably not much of an effect... only had a couple of "bits of fishfingers" in it. Also made sure it was properly fitted seated / slotted in afterwards.

    4. Checked thermostat.
    Wasn't at fault in our case, but mentioning it as it was suggested so many times as being the most likely candidate. An engineer checked it for us with a laser thermometer. Not too sure how... but I think he confirmed it was opening at an expected temperature and causing liquid to flow as expected.

    5. Feeding Coca Cola to the engine.
    This was my favorite. I tried to get rydlyme from Force4 but the guy on the counter had never heard of it. When I described it, he said something like "oh, that? We just use coke, works a treat". After some research (for example video linked below), it seems the Phosphoric Acid mayyy have a cleaning effect. However, most professionals I've talked to say it's ridiculous to use cola, that it won't have any effect. I aim to do this every season, and have done twice thus far:

    (1) buy 5L of Coca Cola (with Phosphoric Acid listed as ingredient, as not all have it now).
    (2) make a funnel out of a large bottle, disconnect seawater intake (I was shown how to do this by an engineer, and ours is above the waterline), duck tape massive funnel on.
    (3) fill funnel with cola.
    (4) shout for wife to start engine.
    (5) keep topping up funnel until all 5L is guzzled.
    (6) as soon as funnel is drained, shout for wife to kill engine.
    (7) wait 24 hours.
    (8) run for a few minutes to flush it out.

    As I say, I'm not totally convinced about #5, but it's cheap. Some people also mentioned something akin to "rodding"... using wires or the like to scrape out the insides lose of gunk, though I never tried that.

    Either way, good luck, it appears to be an elimination exercise. I hope you can get it sorted asap, as the weather has just turned fantastic!

    YouTube: Gorjus Boating
    Boat: Sealine 195

  7. #7
    Join Date
    Apr 2019
    Location
    Wales
    Posts
    366

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Cola is regularly used as a cleaning aid, really good for cleaning toilets too. I say cola rather than coke because some people get really confused. (Coke is the name of many different items)

  8. #8
    Join Date
    Apr 2019
    Posts
    14

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Thanks for the reply vodzurk,

    Sounds like many people have experienced this problem and got through it without it being curtains for the engine !!

    The engine is still raw water cooled so no issue with topping up I did change the impeller however and have got good coolant flow.

    The cola is an interesting idea I had considered it but couldnít see how it would be strong enough, I will give it a go.

    Think Iím going to run the fernox ds-3 through it for a while as suggested by VicS, if that doesnít work go for the brick cleaner and if that doesnít work try feeding her cola and let it sit !! Will try the cola either way though might use it to flush through after using acids and as an extra clean through the entire engine.

    Itís a frustrating task when the weather is so nice, hopefully I will have her in the water by the weekend just in time for the weather do go down hill 🙄 such is life haha

  9. #9
    Join Date
    Apr 2019
    Posts
    14

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    The confusion would include me, is the cheapest roller cola available likely to be the best stuff for the job ?

  10. #10
    Join Date
    Apr 2019
    Posts
    14

    Default Re: Penta Md2b overheating, advice needed, maybe need engineer local to Barry

    Hi Scottie thanks for the help, flow is there so that has to be a good sign just a big difference in volume at the minute, I can get about 5 large syringes full of fluid in the rear jacket and only two or so in the front? Both drains are flowing all be it one much better than the other.

    Will the shims be specific to that engine block ?

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