Overheating

[Murv]

OK, so my old boat is finally sorted out, it's developing full power and really flies. But, now it overheats.
Usual story, I've no idea what sort of temperature it used to run at as it's the first time it's ever been running properly.
I've done the usual things, strainer is clear, new pressure cap on the heat exchanger, new thermostat on the closed system, fresh 50:50 antifreeze in the closed system, both pumps appear to be working.

At displacement speed, no problem, temperature is stable and sits at around 90degC for hours at a time.
As soon as it gets on plane, it rapidly gets to over 100degC and blows clouds of steam out of the exhaust.
On a flat out run last week it jumped to 120degC before it blew all of it's coolant out.
Now, I'm not sure if the problem is the increased revs and fuel burning that causes the overheat, or whether the raw water system cannot draw enough flow when on plane. It's obviously a difficult thing to test!
What I'm thinking of trying is running the boat against the tide (we have a fast tide run here) so that revs are fairly high, but boat is displacing to see if it gets hot. Trouble is I can't run it at too high revs otherwise she'll plane.
The other slight problem is I'm on a speed restricted tidal river so need to limit testing to 6 knots. I can do brief faster runs just upriver in the water skiing area otherwise it's a journey downstream to where the speed restriction lifts, but then obviously a real pain getting back if I suffer engine failure through overheating.

Boat: 22' cabin cruiser, planing hull
Engine: Ford FSDTI (marinised Transit engine) 2.5 Turbo diesel.
Cooling: Jabsco raw water pump through Bowman heat exchanger, water cooled exhaust, turbo and oil
Outdrive: Volvo 270 (as far as I can tell, the cooling system has been removed on this as it's redundant)
Speed: Top speed around 26 knots, realistic cruising probably around 16 knots.

One thing I'm suspicious of is the raw water intake. It's just a conventional, flat, through-hull fitting. From the Googling I've done, some suggestions are that the water intake must be a scoop type, otherwise the raw water pump cannot draw enough through, but other sources seem to suggest that this is unnecessary. However, it's been configured like this for the last 10 Years so presumably it must have worked in the beginning.
Any ideas where I should start? It's a little frustrating finally unleashing all this power after nearly 18 Months of owning the thing, then not being able to use it!

Cheers,
Chris

 

[rafiki_]

Murv, do you know if the engine temps have ever been OK on the plane? Or is this the first time you have achieved these speeds? Perhaps another thing to check if you have not already done so is to see if there are any blockages in the raw water pump inlet. On my boat, both were heavily furred up, with the diameter down to 12 mm not the normal 35 mm. This will make a massive difference to the temps when the engine is working hard.

The people who are the experts on marinised Ford engines are Lancing Marine down at Shoreham. You could give them a call to see if they have any thoughts for you?

 

[oldgit]

You could give them a call to see if they have any thoughts for you?

+1.

 

[Murv]

No, I've absolutely no idea what temperature it ran at, it's the first time it's run properly since I've owned it.
Thanks both, I feel as if I've been pestering Lancing a lot lately! I'll give them a call.

 

[dsw]

where is the intake situated on the hull ?

 

[Davegriff]

For my two pen'uth I suggest checking the jabsco raw water pump. 'Orrible things on the suction side. Try new impellor and o ring. Check plate is dead flat. Should check annually at least.

 

[John_d_Smith]

Last year i replaced my header tank cap with new ones from a local tractor supply company. I then had over heating problems, after experimenting i found it to be the radiator caps which were the wrong pressure. I'd try just sitting them loosely and see what happens.

 

[Divemaster1]

I'm a KIS kind of person, so always want to try the simplest thing first 1, then 2 etc... but of course it is the increased heat from extra fuel burn that cause the overheat ... your coolant should circulate well enough to disperse of this heat....

1) Raw water-flow. do you know that the raw water pump actually is drawing in water, and that water comes out through the exhaust?
It is not un-common to have restrictions in intake (all from closed valve, to crud around intake), or the impellor can be damaged ...(blades missing, or spindle slipping). Changing the impellor would be the first thing I'd try. If blades are missing, you should try to find the missing pieces, as they could lodge somewhere downstream in the cooling system and cause restrictions. Somehow you should be able of testing this .... and yes, if you do not have a scoop fitted, there could theoretically be air introduced around the raw water intake, which would mean insufficient cooling ... you can check this by observing the strainer when running at speed, and if air is introduced, it is one out of two things... once again, do the simplest one first ... a) Seal around strainer lid could be leaking and a better seal must be made... or b) air is introduced through the intake.
2) Heat exchanger - how clean is this one?? If you have restrictions in the matrix (eg build-up of crud... or old impellor blades)here, then raw water will not circulate fast enough to cool the circulating coolant that disperse of the heat from the combustion into the raw water and out through the exhaust.
3) Circulation pump & coolant system .... how convinced are you that this works properly ? Remember that the coolant should circulate in jackets around the cylinders etc... and if engine has been sitting still, un-used, or with poor quality coolant, then these small jackets & water passages will corrode and restrict coolant flow and thus coolant effectiveness.

Just a few thoughts above .... and perhaps one or two things to try before spending too many ££ .... but one word of warning before I stop ... 120 degrees is too hot for a diesel engine !! ....run her like that again, and you'll be at serious risk for visit from Big Bill...

 

[Murv]

Many thanks all, very useful.
Lancing were very helpful. As per Divemasters suggestion, they suggested the first thing is to check the strainer cup at speed to see if it starts to pull air.
Unfortunately this won't be particularly easy. Due to its location, it requires the suspension of ones unmentionables over the alternator fan... However, it is doable.
However, presumably if the problem is water flowing too quickly past the intake, then high revs in idle would show this in the strainer, i.e if the water flow stays constant, then it must be the intake position?

Too address some of the questions:

The intake is on the bottom of the hole, on a flat area, approximately a foot forward of the stern.

1) Yes, it is definitely pumping water, by leaning the boat to one side to lift the exhaust from the water, it pumps nicely at idle.
I will get a new impellor, apparently they should be changed occasionally and I've no idea when it was done. The pump is around 10 Years old and quite possibly hasn't been done for at least 5 Years or so, so it makes sense to do that anyway, and to acquire a spare.
2) The heat exhanger was off a few weeks ago when the new turbo was fitted. It appeared to be fairly clean, but I've no idea how inspectable they really are? I'll assume it is unless the easy options expire as the poor old wallet has taken a fearsome battering getting to this stage!
3) Not really sure on this one. The water pump was changed last Year when the cambelt was done. It certainly pumps water, and will sit at a steady temperature for hours at a time at 6 knots.
It has has had a few coolant mixture changes recently due to works on it, plus blowing out all the old etc. The water in the jacket looked to be clean when I replaced the thermostat housing last week. I don't know how indicative that it, but it didn't "look" to be excessively corroded internally.

Re the pressure cap. This was a new one supplied by Lancing for the fitted chargecooler, it's a 10psi one. But, it made no difference from the old one. I would have thought that higher pressure would help it run at higher temperature without boiling?

I realise now that 120 is way too hot, think I was pretty lucky it didn't seize quite honestly. But, they have a reputation for running hot, following advice from a member on here, and Lancing marine, 90-100degC should be the target range even under load.

Lancing did also suggest running the water intae from outside the boat (carefully!) when at speed to check whether it is the inlet position.

 

[crazy4557]

Get yourself one of the heat laser gun thingy's that will show the temperature at any area that you point it on the engine. This should identify the possible source of the problem.
I picked up one on Ebay.

 

[mtb]

fit a scoop

 

[dpb]

Steam out of exhaust....?
Head gasket maybe?
Worth doing compression check then.

 

[JOHNPEET]

Hi Murv,

With the boat on the plane, I would have thought that the through hull intake would be seeing a mixture of air and water, therefore reducing the efficiency of the cooling overall. Is there any chance you could go back to using the water intake on the outdrive leg? Not familiar too much with the 270, but I used to have a boat fitted with a 280 and the water intake was low on the leg so always in good water. The only cooling bits in the leg were channels and the flexible pipe to the shield.

 

[David2452]

fit a scoop

+1 Separate scoops are easy to fit and available in most decent chandlers, a flat intake becomes a venturi at speed and the water (and air) flowing over it will actually be trying to suck water out whilst the pump is trying to suck it in.

 

[Davegriff]

Probably way off here, but I just noticed that you have a 50:50 antifreeze mix. Antifreeze is not as good a coolant as water - you could be loosing a possible 10-20% cooling capacity over a straight water (no anti freeze, not recommended) coolant at high revs. Could matter if system is already on its limits.

 

[oldgit]

The really keen will change the impellor every year.
It should be done every two years.
Have my suspicions that one of yours will not have been replaced for years.
If left in one position for to long the blades harden,develop a "set" and do not deform properly as they rotate in chamber.
Hence OK at tickover but not moving sufficient flow to cool engine at high revs.
A new impellor would be my first action.
Dead easy job.
Remove facing plate and lever out old impellor with expensive proper device or old screwdriver,your choice.
Check for debris in chamber,vital if any blades or parts of blades are missing.

 

[Murv]

Many thanks all.
Have just returned from the boat...
It's simply not possible to monitor the strainer, you'd need a head 3" wide. Did manage to poke a phone camera down there on video and it's pumping water through nicely at tickover. I didn't have time to let it warm up properly so couldn't carry out the high revs test but will take it out tomorrow and give that a try.
There is no access to the raw water pump either, but again with the phone camera I managed to make out a few numbers so I'll try and order an impeller based on what I have.
The pump will need to come off to change the impeller. I did notice a couple of large blobs of rust, are they likely to be the retaining bolts? are the pumps generally easy to remove?

Fitting a scoop won't be too big a deal, the boat will be coming out in the next few weeks so it could be done then if the new impeller doesn't solve the problem. I wouldn't want to fit one if not required as there is an awful lot of debris in the river, and it sits on soft mud at low tide. Anyone recommend a supplier, or what to ask for? I just got bewildered looks in the chandlers earlier.

I can't go back to using the intake on the outdrive, as far as I know, I believe everything has been blanked off. Certainly the exhaust hole in the transom has been filled.
I'm reluctant to change too much, I have all the receipts from the owner who repowered her. He spent many thousands on the project so it must have worked in its current configuration originally. Although, it does seem an absolutely ideal place to draw water from.

Antifreeze: I always thought that antifreeze was a more efficient coolant? is that not correct then?

So, first things first, I'll get the impeller changed as it needs doing anyway. Hopefully that will solve all the problems! I think the boat did sit, unused, for long periods of time in a past life so it's probably in a bad way.

Thanks all,

Chris

 

[omega2]

Do what you did to the intercooler, as I described, remove the end caps, remove the matrix, and clean it, my bet is that it full of c----p as was the intercooler.

 

[gordmac]

Is the thermostat working ok?
Can you add a length of clear pipe you can look at in the raw water system to look for air?

 

[James L]

As far as I remember, you can just remove the thermostat temporarily to see if it is the problem.

But sounds to me like the impeller is a good bet, I had one slightly over heat as it was airlocked, had to be replaced even though it looked perfect, as soon as I got up to speed the engine started overheating.