Perkins 4-108 0verheating

I am having a problem with mild overheating on a Perkins 4-108 in a Gulfstar 36. It is not extream, but it is disturbing because it shouldnt be. It will run up to ablut 5 knots until the temp rises to 200F. If I then back off on the throttle it will cool down imediately. Any speed above 5 knots will cause higher temperatures.

I have,

1) removed and cleaned the heat exchanger in an acid bath. It had about half the pipes completely clogged. No Change.

2) removed and checked the thermostat. No Change.

3) replaced the impeller on the raw water pump. No Change.

4) cleaned and re gasketed the raw water filter. It was leaking air, but not real bad. There was minor improvement.

I have not yet removed the fresh water pump because I have assumed that like an auto water pump it is bullet proof unless the shaft breaks. Maybe that is where the problem is though as I can think of nothing else left to look at.

There is what looks to be more than suffient water comming out the exhaust and the bottom is clean so I dont suspect clogging in the raw water intake.

The engine timing seems to be fine since there is no smoke, it starts easily, and it gets about 0.65 GPH which is fairly normal.

Any one have any ideas????

 

What have you done since this problem occured?

 

All the above mentioned items!

 

Ok, that was my fault I mis- worded.

Has the engine ever been ok ,---I mean was there once a time when it kept cool . Or have you just bought it.

 

Ok, that was my fault I mis- worded.

Has the engine ever been ok ,---I mean was there once a time when it kept cool . Or have you just bought it.

 

I purchased the boat with engine in April in FL and in May I drove it home, under power, no sail, to Corpus Christi Texas, 220 engine hours in 35 days. Total engine hours are 427. The boat had been sitting for over 5 years so its to be expected that there would be some deterioration of the cooling system. In the beginning I had no water temp guage. I used the "put your hand on the engine and if you can hold it there for 3 seconds, all is well" method of guaging engine temp. Three days into the trip I repaired the water temp guage by replacing the sender. This is when I noticed that the temp was rather warm at 5 knots. I kept the temp below 200F for the entire trip, sometimes being able to make 6 knots and most other times about 5 knots or a bit over, mostly into the wind (the reason for no sail). This is driving an 18x18 prop through a 2.57 : 1 Velvet drive transmission. The average fuel consumption was 0.671 GPH for the entire 1400 miles. No smoke. Easy to start.

The temperature rises to thermostat temperature when idling at the dock and remains there (165F). But as soon as the drive is increased above idle the temperature also rises.

The bottom is clean, the prop is clean, there is considerable sea water exiting the exhaust pipe. Sea water temp is 80+ degrees F. The fresh water is clean and not contaminated by sea water. After installing a water recovery tank in the engine, it uses NO water even after a long run of many hours. Before the recovery tank placement it used about a pint of fresh water every 10 hours of operation as it was being pushed out the cap into the bilge.

The items I mentioned as being R&R'ed were done in the order mentioned as I tried to resolve the problem. When I found that half the heat exchanger tubes were blocked I thought I had found the problem, but it didnt make a difference at all. When I discovered the leaking seal on the top of the raw water strainer I again thought I had found it, but the improvement was miniscule if any.

I have two more ideas, one simple and the other more dificult, check belt tension and R&R the fresh water pump. I hadnt checked the belt tension as it LOOKS fine when running and the alternator is charging the batteries fine. But I suppose it would be wise to check for the 10mm depression on the long side just to make sure that is NOT adding to the problem.

I am also thinking that maybe the engine needs an acid rinse but dont know which product to use. I want to use something that will not be a problem to leave in the engine for a while as I may be interupted in the middle of the job so I dont want to eat the engine up from the inside out...# The best time to do this would be BEFORE I R&R the water pump as I will have to drain the engine to do that anyway.

 

--what i would be thinking first of all is was the sender compatable to your guage . In actuall fact can you acertain that the engine is actually over heating. As you say the hand on the engine is not very accurate.

You could buy a cheap mechanical temp guage and fit it permenantly to the engine as a back up ( i usually do this ) Some times there is a place for a second sender. If not you could just try it temperary.-- or remove the sender and get a pan of boiling water and a thermometer. It would be reassuring to confirm that this is a overheat problem and not a guage problem

 

I have already gone one better. I have a laser "no touch" temp gun and the guage is accurate.

 

In that case I would suggest you go ahead and check the fresh water pump. I have heard of them coming apart or loosing fins but I have never experienced this.
Have you tried running the engine with out the thermostat. I cant recall now but I remember the thermostat is quite a chunky one and I cant remember if its one of those that covers ports as it opens others. In other words is it the right one?

Have you tried running the engine in the dock with a fresh water hose.

I once experienced an impellor pump that was worn out and new impellors did not cure the problem --the pump body is bronze and had worn away. It was eay to tell as the impellor blades barely touched the body. What was difficult was making the owner believe me. A new one finally convinced him after many days of procrastination.

 

Not sure what you mean about running it at the dock with a hose?? At the dock it doesnt overheat. Its only when underway and under load. At the dock it sits on 165F as long as you want to run it. In fact at 3 knots it will stay below 170F.

But I dont have water at the dock anyway.

The raw water pump impeller fits very tight. The old one was fine but I changed it out ANYWAY just so I knew it was right. And, there is lots of sea water coming out the exhaust so it appears to be doing a good job. Its putting out as much water as my 6-354 did on my last boat and that engine was much bigger and always ran very cool.

Its very puzzling.

 

Yes, the thremostat is a prety normal one like is used in most automobiles. I checked it in a pan of water and it worked fine.

 

Ok well in that case I will tell you of a overheat problem I had on my cat. The port engine would just go a shade over normal . It was ok but I couldnt take my eyes off the guage. I did all the stuff you did and these engines were 120 hours only. The problem was cured by grinding about 2 mm off the leading edge of the water intake. What was happening was ( ok I know you dont go that fast but) the water was not going into the intake at higher speed. After this mod I found I had rock steady temp guages and I even had to change the raw water strainers to hold the now pressured system.

Maybe not relative but Im getting a bit down on ideas now.

have you got a normal open water pick up or one of those strainer types, if so is it cruded up? or over antifouled reducing inflow?

I would get that fresh water pump off too and have a look.

Also did you check the thermostat against a thermometer? I would run the engine with out it and see what happens.

 

You seem to have well thought out set of details. If you complile everything above into one comprehensive report, I think you might get some help from the technical people at Perkins.

I've had some dealing in the past with:
Perkins Power Corp.
55 Industrial Loop North
Orange Park, Florida, 32073, United States
Phone: (904) 278-9919
Fax: (904) 278-8088

But the guys at the factory have also been helpful in the past. I don't think the 4-108 has ever died in their hearts. There must be farmers, taxi drivers, fork lift opperators and even boaters the world over who still want help with their engines.

Sabre Engines Ltd
22 Cobham Road, Ferndown Industrial Estate
Wimborne, Dorset, BH21 7PW, United Kingdom
Phone: [44] (1202) 893720
Fax: [44] (1202) 851700
E-mail: post@sabre-engines.co.uk

 

OK, I will try it without the thermostat and see what happens. I checked the thermostat in a pan of water on the stove and a candy thermometer and it opened on que at exactly the temperature it should.

The raw water intake is through a flush through hull and a Perko strainer which I thourally cleaned and refurbed with new gaskets since it was leaking air at the top gasket which was a homemade gasket.

 

I summarised all of my posts and sent a copy to Perkins Power Corp as you suggested. I am anxiously awaiting their reply.

I have also aquired a bottle of Prestone Super Radiator cleaner that was recommented by the local Perkins mechanic who is as baffled as I am about this problem. I will try an engine flush tomorrow then after I have drained it I will check out the freshwater impeller while the engine is "dry".