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Preventative Maintenance Tip for Cooling System

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Marc97gt View Drop Down
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    Posted: 25 March 2012 at 2:55pm
Just a preventative maintenance note on the cooling system.

While taking the boat around to the yard for winter lay up the DV8 ran fine but the temp gage would spike up from 120F to 180+F with load on the engine. Pulled the thermostat out and ran the boat around to the yard.   Spoke to Keith at Crinmar and he suggested boiling the thermostat in vinegar for 20 minutes to clean off the crud, in the event the problem was due to a stuck thermostat. 

 Launched  the boat  this Spring with the cleaned up thermostat installed and the temp spiked up after about 5 minutes of running. 

I pulled the thermostat and ran the engine lightly to keep speed at 3.2 kts.  Cylinder was very warm to the touch.  I pulled the feeder hose that connects to the right angle fitting  on the bottom of the cylinder and the thermostat block , then blew through the hose and got some air through but it was clear there was a blockage somewhere.  

Got the boat home and pulled off the fitting on the bottom of the cylinder and found it was plugged with flaked rust. Cleaned it out and installed it with a home made gasket. Everything is fine.

Just says after 27 years of use, it needed cleaning.  If you have not checked yours, might want to.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Winner Quote  Post ReplyReply Direct Link To This Post Posted: 21 May 2016 at 11:23pm
The issue with engine overheating has been discussed in several other threads as well, but since this thread is dedicated to this topic I thought I'd post my recent experience here.

It has been said that internal engine corrosion only happens in salt water boats or boats winterized without antifreeze (i.e. dry).  To the best of my knowledge, my boat has always been freshwater; but as the fourth (at least) owner, I can't verify the steps taken for winterization in the past.

First the disclaimer: while I do like the Bukh engine overall, especially for it's reliability in starting and ease of operation, I think it has one serious, potentially fatal, flaw, and that is the narrow passages at key points in the cooling system.  I feel this is a major issue not only because of the ease in which these passages can become plugged, but because of the potentially disastrous consequences without any outward signs of trouble.  Not a robust design IMHO.

One such point is the elbow at the fitting where the cooling water from the engine merges into the exhaust elbow.  The fitting, as previously discussed by Frank in another post, is only 1/4" ID and could easily be plugged by any debris or flakes of engine corrosion.  The solution is to install an inline water filter in the hose between the thermostat and the inlet port to the exhaust manifold on the port side.  A filter like the Jabsco 36400-0000 does the job nicely:  http://www.defender.com/product3.jsp?path=-1|51|2234255|2234258&id=121067

The other benefit is that the clear casing is another place where you can check to ensure water flow.  Be sure that the hose clamps are not too tight (crushing the barb and blocking water flow) and not too loose (allowing air in which would reduce water flow) and that the filter is oriented the right way for water flow!  I have had this filter in my engine for 4 years now and it has been very helpful in trapping debris.

The other weak spot in the system, described above, is the one I just dealt with.  On our first motor out of the boatyard this year after 20 minutes of running at 1700 rpm in smooth water, the engine overheat alarm went off.  There was no other indication of  any problem as cooling water was coming out of the boat exhaust normally.  

After checking the hoses and thermostat, I traced the problem to the water inlet port below the air intake on the starboard side.  To remove this inlet port housing you'll need to remove the starboard bulkhead (unless you are a contortionist).   

There are two bolts underneath you'll need to loosen with a 10mm box wrench to remove the inlet housing.  When you remove the housing, water (and maybe sediment) will gush out so have paper towel handy.  The pictures below show what came out of my engine.  I was astonished at the amount of flaked metal sediment!  The picture with the paper towel is showing only 15% or so of the total amount that came out.  The inlet pipe was so densely clogged that I had to chip the sediment out.

https://goo.gl/photos/S5gQsL83bbgWegSd8

I also highly recommend that after cleaning the inlet pipe, you flush the head cooling passages.  To do this it is best to simply remove the thermostat housing and pour water in from the top, allowing it to flush out the bottom. I did this and LOTS more metal sediment came out.  I also used my finger to plug the bottom while filling with water to the top of the head which I think allowed for a better flush.  It's also recommended you use some sort of scraping tool to reach up into the passages from underneath to make sure there is no more flaking metal that will easily come off and recreate the problem.

Once complete, you must cut a small paper gasket (I used 1/64" paper gasket material bought at Canadian Tire) and lightly coat with sealant on both sides of the paper gasket (I used Permatex Form-A-Gasket #2).  Blue Loctite on the threads of the two 10mm bolts.  Reassemble the valve fitting with gasket and bolts in place, then place underneath en masse and tighten bolts.  I let the Loctite cure for 24 hours prior to running the engine, although this may not be necessary.

The thermostat housing is best reinstalled with anti-sieze compound on the four allen bolts.

I plan on checking this again in two years to see if I have had any further sediment accumulation.  If you have never checked this on your engine, I highly recommend doing so, especially since it may clog and overheat your engine with no outward signs of trouble before it is too late.


Edited by Winner - 21 May 2016 at 11:26pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bill Layton Quote  Post ReplyReply Direct Link To This Post Posted: 22 May 2016 at 7:47am
This blockage which occurs on nearly all older engines that have not had their cylinder head completely rebuilt is very common and the result is that it overheats the head and blows the head gasket. It also causes the head to warp. So when we rebuild them the deck on the head must be milled to get it flat again. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2016 at 12:20pm
Thanks for the info and pics, it is  shocking how it was blocked  , mine will get done this winter . I am adding an additional bolt on engine temperature gauge and alarm as I  do not trust the rudimentary system the boat came with to do much beyond tell you its game over .  100 bucks worth of insurance . 

Edited by John Mills - 30 May 2016 at 12:21pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Seawolf Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2016 at 5:56pm
John,

Have you picked out a gauge and temp alarm for your boat? If so I am curious what you choose, I would like to add a peace of mind to my boat.   Thanks.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bill Layton Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2016 at 6:04pm
The water alarm that comes with the engine works fine. Ask Chris who just posted the pic of his clogged system. His alarm went off first so he knew there was a problem. Putting in a filter won't help this situation because it's sediment that collects at the lowest point and most restricted point on the engine. The only way to be sure your not clogged is to take it apart and check it. It's not a huge job so if your unsure, take it apart and verify it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2016 at 11:01pm
I will be taking mine apart and cleaning   , but truth be told I do not trust the 30 year old alarm , after all we would not have boats with warped heads if the alarm always worked in time .  Given mine starts with the flick of a key I would hate to have to rebuild it . 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2016 at 11:10pm
The Gauge I ordered is made in Australia  on Ebay "DIGITAL TEMPERATURE GAUGE with AUDIBLE ALARM Engine Guard EG01/1 BOLT-ON SENSOR" 

$78 bucks US , free shipping . Does not replace the sensor in engine but instead adds a sensor bolted onto the block to sense block temp , not water temp  . I understand the engine can over heat if a passage gets blocked while still pumping nice cool water out back . This should catch that while giving me a temperature gauge .  I will report if it seems to work 


Edited by John Mills - 30 May 2016 at 11:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2016 at 8:06am
Update on the aftermarket alarm .  I bolted the sensor to a threaded hole on the block next to what appears to be a frost plug starboard side . It senses the cylinder block temp not water temp while the factory alarm senses water temp .  The display is right above the Bukh engine panel, bright and easy to read . Alarm set point is adjustable and alarm has the option to monitor oil pressure too (have to buy the kit)  .  I now have two alarms , the factory one and a back up totally separate .  Engine runs at 140- 165 deg depending on load , watching it it appears you can see the thermostat open and close as the temp goes up and down , after 5 hours of motoring fairly hard about 151 deg and actually spikes to the max when you go to idle after motoring hard .  I set the alarm to go off at 170 deg . 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Winner Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2016 at 12:31pm
In my instance, as Bill mentioned, the alarm did go off in time to warn me of a problem.  However I had another instance years ago where a complete water blockage eliminated all water flow through the engine and by the time I realized, the hot exhaust had melted a hole in the plastic muffler.  I was fortunate the head did not warp.  Yes this was a rookie mistake (I had bought the boat only one week prior), but in this instance, the engine overheat alarm did not trigger in time.

For $100, John's solution seems quite reasonable as an extra protection and I really like the ability to see the actual temp.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Winner Quote  Post ReplyReply Direct Link To This Post Posted: 22 June 2016 at 10:24pm
Thinking more about my last post, I'm not sure if a temp gauge mounted to the engine block will help with a water blockage situation.  In this instance, hot exhaust is directly in contact with the plastic (in most L28's) muffler which will melt the muffler before the engine block reaches overheating temperature. 

What would be best is some sort of water flow meter, or temp gauge in the exhaust pipe itself, in combination with an engine block temp gauge.  This combination will best cover instances of both engine block overheating  (due for example to blocked lower passages) and lack of water flow through the cooling system.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 25 June 2016 at 10:07am
The temp alarm is able to have two temp sensors with different set points . you can put one on the exhaust and set it for a different temp to alarm at . Going to do that myself . You can order it with both sensors and I am regretting not doing that , now I have to order it separately .  The alarm is for cars and set up so  you can monitor the temp of your transmission too . Seems no reason we can not monitor sense the exhaust temp with it instead. 

I believe it will cycle back and forth displaying the two temps alternately. 

So what I have is I am not sensing the water temp, I am sensing the block temp , the factory switch senses the water temp and if you have flow at the sensor but a blockage in the block it will not go off near as I can tell . Mine senses the temperature of the cast cylinder block . I will add the exhaust sensor this winter . 


Edited by John Mills - 25 June 2016 at 10:55am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Winner Quote  Post ReplyReply Direct Link To This Post Posted: 05 July 2016 at 12:36pm
I ordered the dual sensor you mentioned above.  I will attach one sensor to the engine block and the other I think I will attach to the base of the muffler (using a large stainless hose clamp), directly underneath the exhaust inlet as in a water-starvation situation, this is where it will get hot/melt first.  I'll report back once I have it installed and have an idea of normative values.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fatjohnz Quote  Post ReplyReply Direct Link To This Post Posted: 25 July 2016 at 7:42am
You guys saved my butt. Thanks.
I'm heading out for a week long racing/cruise tomorrow and I pulled the lower cooling pipe this past weekend. It was clogged with sediment. I'm lucky the engine hasn't blown. Thanks for your proactive postings as always,
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 30 October 2016 at 9:41am
Originally posted by fatjohnz fatjohnz wrote:

You guys saved my butt. Thanks.
I'm heading out for a week long racing/cruise tomorrow and I pulled the lower cooling pipe this past weekend. It was clogged with sediment. I'm lucky the engine hasn't blown. Thanks for your proactive postings as always,
js


I take it the factory alarm did not go off ?  I pulled that cooling pipe yesterday and mine was perfectly clean . I suppose the old owner must have done it . 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bill Layton Quote  Post ReplyReply Direct Link To This Post Posted: 30 October 2016 at 9:45am
The original owner of that boat never used it.... I doubt that engine has more than 20 hours on it! Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 30 October 2016 at 10:31am
Originally posted by Bill Layton Bill Layton wrote:

The original owner of that boat never used it.... I doubt that engine has more than 20 hours on it! Wink

Motor has more now Smile, starts with the flick of a key . Question , the key shut off can accidentally be left on burning it out I am told , was thinking of just moving it to a button beside the key so you can not  accidentally leave it on . Has anyone done this ? 

 As to the boat , the whole boat seems never used , but really really dirty . All cleaned now and largely restored - all painted and varnished down below  . Tons of maintenance done to it . Lots of stuff that would have broken if he used it -replaced prop , all the clutch handles , all the lights upgraded to LED  ,serviced all winches , new inboard tracks , glassed hull at chain plates , beam of destiny ,  the hull gasket for the sail drive, all new instruments and   new slides for companion way , new gasket for hatch , re bed everything (no more leaks) , pulled the fuel tank and dumped out the strange color fuel,  restored the trailer and moved the boat forward on it too and a few neat toys like a below deck auto-helm . That's the short version of the list Painting the engine and pulling the holding tank for cleaning this winter. 

Love this boat , as you probably know I got a smoking great deal on it and this one as you know was never used so its like new ,  but I put a ton of money in and even more time. Kind of like a barn find on a classic car , sure it was never used but you had better go over absolutely everything before you drive it and be prepared to replace lots of plastic bits  . 


Edited by John Mills - 30 October 2016 at 10:41am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bill Layton Quote  Post ReplyReply Direct Link To This Post Posted: 31 October 2016 at 10:49pm
Yes a boat burned to the waterline and sank in FL because of this. I've seen burnt wiring harnesses to engine more than once.

I installed a 5 amp fuse holder and my worries are over. I put it behind the ignition panel, easy to do. It's the black wire to the fuel shut off solenoid so yeah a button is fine too, thats good.

For those who had fried their  "shut off solenoid" replacement was always very pricey, so we ran a cord from the fuel shut off lever to under the ignition panel. Sounds like you are having fun. Keep up the good work!




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Post Options Post Options   Thanks (0) Thanks(0)   Quote John Mills Quote  Post ReplyReply Direct Link To This Post Posted: 01 November 2016 at 8:28am
Thanks Bill , I probably will do both . Seems a pretty silly error on Bukh's  part. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Bill Layton Quote  Post ReplyReply Direct Link To This Post Posted: 01 November 2016 at 8:44am
It's the usual story... if everyone read their manual they would know that they are not supposed to leave the key  in the off position.  In hindsight I would say only the small minority read the manual. 
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