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Old 01-02-2007, 15:37   #16

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Agreed, Paul. Just like supercharging or nitrous systems, a turbo is just another way to cram more at the combustion chamber. The engine has to be carefully designed to take all the excess stress... or else shorter life.

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Old 01-02-2007, 15:44   #17
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WRT the original post.

Yes, it is a great engine. I know you would probably not re-start it without the obvious (cooling) but another consideration is the fuel supply.

Running the IP out of fuel not only will cause you to have to bleed it, but can cause damage as the fuel cools and lubricates it.

Just a couple more 2 cents. Hope you get long and reliable service from your classic motor.

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Old 01-02-2007, 16:36   #18
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Cheap engine, expensive installation...

I am learning to live with my Ford 2402E with Kanzaki gearbox but only because repowering is so expensive, time consuming, dangerous and tricky with few skilled workers able to do it.
I can see little advantage in using an older engine as a primary installation. The additional cost of a new engine ($A10,000?) is small compared with the ongoing costs and problems of an old engine.
When I get the next big bill from my engine I am planning to put in a Deere 4045
with a ZF45 Transmission.
This is a low stressed diesel, the modern equivalent of the big diesels of yore.
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Old 01-02-2007, 16:43   #19
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But at a cost of more fuel consumed fuel due to air forced in to aid the combustion.
Oh absolutly. Infact, just craming in more air achieves nothign. the only reason you get more HP is to get more fuel into the chamber and then you have to have the air to burn it. To be more technologicaly correct, the Turbo itself does not give you the increase in power. It is the ability to burn more fuel that gives you the increase in power. So your IP and in most cases the injectors as well, have to be adjusted to be able to deliver more fuel.
Turbo's and super chargers do the same thing. The reason why you tend to see turbo's on boat engines is that the turbo has a few advantages. It can quieten down the exhaust, it produces power in the mid to top end RPM range where you tend to need it more adn if you should happen to be a vessel that can come clear of the water in a ruff sea, the exhaust pressure drops whent he engine loses load and thus the Turbo does not cause the engine to over run. Do that with a super charger and you will be picking up pieces of engine. Superchargers or "blowers" work well on large slow reving engines and the two stroke Diesel. The two stroke requires the crankcase to be pressurised and thus requires constant air pressure.

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Old 01-02-2007, 22:54   #20
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4108 Perkins

Thanks for all the positive comments.

Wheels, water pump">Raw water pump has been removed for overhaul and yet to be re-fitted, but I know that impellors will self destruct if run dry. Thanks.

Faith, no fuel in tanks yet, so pumping through and bleeding system was always assumed to be part of the process any way.

Thanks for all the imput and encouragement.

Fair winds to all

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Old 03-02-2007, 09:50   #21
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My 4-108 starts right off every time but leaked like a stuck pig when I bought the boat . Did the best I could tightening all gasket bolts etc and put in a no leak oil additive - now it might leak an 1/2 ounce over 4 hours run time which is caught by drip pads. I think it's as good as it gets - any other stop leak ideas out there beside pulling the engine?
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Old 03-02-2007, 10:54   #22
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Overheating problems have occurred in these engines more because owners overestimate their hp rating and install propellers which are too large or have too high a pitch. It is not the engine's fault in more cases than not.
Great engines. Look where they were made. I used to ask my friends, "Why doesn't the UK make a lot of computers?" The answer of course is that they couldn't figure out how to make them leak oil. : )
I have a 66 Triumph TR4A and have ridden BSA and Triumph bikes. All leaked oil no matter what I did.
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Old 07-02-2007, 17:25   #23
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While rated variously at 42HP, 47HP, 50HP, etc., this engine is overrated. It's a small engine, despite it's bulk and weight, and should be rated down around 30-35HP in actual use.
I contacted Perkins in the UK with my serial and model number for the 4-108.
They e-mailed all the details including the HP rating.
For my engine it was 51 HP.

That being said, the 51HP is measured at 4000 RPM which is more like "war power" but the max continues recommended by the factory is 3000 RPM.
The HP at the reduced RPM would obviously be less.

On a few occasions I have had to use full power and the old diesel will deliver, but slowly overheating.
The emergency occasions when I dialed in 4000 RPM would be when bridges was about to close on me (too late to stop) and to avoid collsions.

At max power it will make big noise with boat speed at 7 knots or more, foam flying, smoke blowing and in general it feels like the engine is coming apart.

(My ship is 33 feet with a 25' water line)

I have also ran a 42' Jouet Ketch with the same engine and that boat was faster with less RPM..Probably the much longer waterline.

As for the leaks:
I have a small/slow leak at the aft seal. It seems to stop whenever the boat is used every day.
Just sittin for months, then running it will spit some oil, but not much at all anymore.
It was worse just after bought the boat 8 years ago.
I have never attempted to tighten things up or try to "fix" it...No room back there.

Using an oil absorbing blanket under the engine and in general it stays white for 100 hours between oil changes. Except when rarely run, then the blaket goes gray, then black.

Have overhauled the cooling system and done other routine maintenance. Still overheats slowly but surely whenever I run at 2600 RPM or above for more than a few minuttes.
Don't think I am over-propped as the 4000 RPM can be reached if needed.
Also boiled out the heat exchanger and swapped with the spare one back and forth.
Have a hunch my intake may be too small.

Not a big problem, getting my 5.3 knots at 2100 RPM, 5.6 at 2400 an 5.9 @ 2600...Pretty much all I need to do.

Found 2100 RPM to be the best power setting for lowest fuel consumption and best speed..It also agrees best with the hull and everyting else. (No black mustache on the transom from soot)

Fuel consumtion @ 2100 RPM is right at 0.6 gallon per hour.
Tried with a taller prop, got much more speed, but the GPH went up to 1.0. Probably overloaded the engine as well.
Have 2 props and have had both repitched and balanced to find the best combo, think I have it now....

Love my 28 year old 4-108, hope she will last another 28.
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Old 25-06-2008, 13:58   #24
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I had a perkins 4-108 in my 37 ft. Irwin that has run for years without a minutes problem.Unfortunately a oil line broke while the engine was running and I was away from the boat and it locked up.So I am now in need of a used perkins 4-108 to replace it old engine with. If anyone out the knows where I might find a used take out in good condition please let me know.Thanks Vernon
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Old 25-06-2008, 14:34   #25
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Try Foley Engines in MA....they may have a short block, or can point you in the right direction.

Foley Marine & Industrial Engines

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Old 25-12-2013, 15:33   #26
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Re: Perkins 4-108

I am looking for the hex tool for removing the injection pump on a perkins4-108, or advice on what size allen wrench needed for the job?
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Old 26-12-2013, 05:34   #27
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Re: Perkins 4-108

I used a 1/4" rachet and about 15" in extensions. I then took an allen head wrench (either 7 or 10mm, sorry), cut off a piece and inserted the piece in the right size sochet for that allen head bolt.
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Old 26-12-2013, 05:45   #28
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Re: Perkins 4-108

On edit, I am thinking that the size is 7/16"; sorry but its been a while since I did this.
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Old 26-12-2013, 07:16   #29
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Re: Perkins 4-108

why didn't you just use a 7/16 socket? thanks, andy
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Old 26-12-2013, 07:52   #30
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Re: Perkins 4-108

i love my ran great, as long as the oil was able to leak out a little... we got it to no longer leak, motorsailed from zihuatenejo to barra de navidad, a mere 200 miles up hill, and anchored,,, when we went to pull anchor, suffered runaway diesel less than 5 min... which was apparently too long,and now have seized engine we are going to rebuild...
you folks who also sought assistance here and found the unmentionable one, i was able to converse somewhat with that individual, and on basis of that conversation alone, i would never use him either to seek an outside source nor to even borrow a wrench from. wow. he has absolutely no use for 108s called them extinct and said it is 10,000 usd to rebuild one.. omg .. what a jerk. sorry. but it is truth... i am relieved to know i did not choose him.
i know there are many places here to machine parts, and there is even a specific perkins shop...despite the j word saying closest is guadalajara... so unimaginative.
we WILL resurrect my multicolored marvel and proceed onwards.....properly.
kinda. and for a tiny fraction of the j words estimate....rodlmffao.

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