Higher-hour DD 4-53's

[Mako]

I know we've had almost as many Jimmy threads as we have had anchor threads. I've owned 6-71's before but my hours were lower than these 4-53N's of 107hp with 8000 hours. These are 50 year old engines, never rebuilt. On a trawler, not a sport fisherman, so will assume for now they've not been pushed too hard all their lives.

Just wanted some input before the mechanic inspection/oil analysis.

With this many hours, assuming the inspection/analysis doesn't indicate major issues, what type of preventive service would you expect to need, perhaps drop some new heads on them, or such?

 

[Comodave]

I had 6V53s in a previous boat and never did much of anything beyond the regular maintenance. Nice thing about the 4-53s is that there is only 4 cylinders so it will be cheaper than a 6 to work on. I wouldn’t be too concerned if they test ok and appear well maintained.

 

[tiltrider1]

I like 4-53n's and the 8,000 hours doesn't scare me. There is some risk of needing an overhaul but the engines are fairly inexpensive to overhaul.

That said, you really don't mention how big a trawler. If we are talking about something 35' or small then I have very little worry as these engines have done very little work. If they are in a 50+ then I'm a bit more concerned but only a bit. If you are buying a 50+ boat then the overhaul cost on a pair of 4-53n's is going to be one of your cheaper bills.

Properly takin care of these should be 28,000 engines.

 

[O C Diver]

As has been mentioned, very old engines generally aren't limited by their design, but more by the owner's use patterns and maintenance. 8,000 hours over 50 years equates to 160 hours per year. That's fine as an average, but not if the hours were higher when operated and the engines sat for 5 or 10 years.

I find it hard to imagine that some seals won't need to be replaced and maybe the injectors after 50 years. In a worse case scenario, I would want a rebuild price including removal and replacement (unless you can do it yourself) before going forward.

Ted

 

[sunchaser]

Tell us about the boat. As already mentioned, size and model. FRP?

Visually, the engines and ER will provide some strong hints as to owner care and engine’s health. Generally marine age is as much an issue as hours. Even with an OK from a mechanic, Ted is correct, plan on doing some engine work.

The 4-53s are a good engine. Me? Old engines and old boat so anticipate some serious after purchase TLC $ if you plan on any serious cruising.

 

[PierreR]

At 107 hp I am assuming N45 injectors and run at about 1,600 rpm. That is not a lot of hp for that engine. 453's are sleeved and can be rebuilt without removing them from the boat.
There are over 2 million of them in military vehicles around the world. They are very heavy for the amount of hp and that translates to high engine hours between rebuilds.
Cons:
Heavy
Loud
Leak oil
Not as fuel efficient as a four cycle diesel

Pros:
Bullet proof
Long lived
cheap to rebuild
pump a lot of fuel (can be used to balance fuel between multiple tanks)
loss of fuel economy more than offset by overall costs.
Can run multiple add on accessories.

Mine run fine with 1,760 hours on them since new

 

[Ken E.]

At 107 hp I am assuming N45 injectors and run at about 1,600 rpm. That is not a lot of hp for that engine. 453's are sleeved and can be rebuilt without removing them from the boat.
There are over 2 million of them in military vehicles around the world. They are very heavy for the amount of hp and that translates to high engine hours between rebuilds.
Cons:
Heavy
Loud
Leak oil
Not as fuel efficient as a four cycle diesel

Pros:
Bullet proof
Long lived
cheap to rebuild
pump a lot of fuel (can be used to balance fuel between multiple tanks)
loss of fuel economy more than offset by overall costs.
Can run multiple add on accessories.

Mine run fine with 1,760 hours on them since new

A good assessment of 2-cycle Detroits generally. They are loud, both at the exhaust and also engine mechanical noise. Parts are available but check to see who in your area will work on them. My shop in Bellingham stopped a few years ago when their Detroit guy retired. With all the Alaska fish boats in the Ballard area, you'll likely find some knowledgeable service there.

 

[Lepke]

With care, those engines can go 30,000 hours. They can run at the continuous 2400 rating all day. Keep the oil and filters clean. It pays to have clean fuel.
My current DDs are 1947. Rebuilt 12 years ago. Changed to 4 valve heads and got an extra mile per gallon.4 valves allow better removal of exhaust.

 

[PierreR]

With care, those engines can go 30,000 hours. They can run at the continuous 2400 rating all day. Keep the oil and filters clean. It pays to have clean fuel.
My current DDs are 1947. Rebuilt 12 years ago. Changed to 4 valve heads and got an extra mile per gallon.4 valves allow better removal of exhaust.

Was not aware of the fact that you could buy a different head. With better valving you might be able to muffle the noise a bit.

 

[rslifkin]

Was not aware of the fact that you could buy a different head. With better valving you might be able to muffle the noise a bit.

I'm not sure about the 53 series, but for the 71s, the early years had the 2 valve per cylinder head, then they switched to the 4 valve head later on, which helped efficiency a bit and increased power potential. Not sure it did anything for noise. 92s all had 4 valve heads.

 

[PierreR]

I'm not sure about the 53 series, but for the 71s, the early years had the 2 valve per cylinder head, then they switched to the 4 valve head later on, which helped efficiency a bit and increased power potential. Not sure it did anything for noise. 92s all had 4 valve heads.

Mine are 1977. I have the shop manual and will look there for answers. I probably have about the best already. Together they burn 3 gph at about 7.4 knots unless the stabilizers are on and then it drops to about 6.9 at 3gph. Waterline length is 38' and displacement19 tons.

 

[rslifkin]

Mine are 1977. I have the shop manual and will look there for answers. I probably have about the best already. Together they burn 3 gph at about 7.4 knots unless the stabilizers are on and then it drops to about 6.9 at 3gph. Waterline length is 38' and displacement19 tons.

Lepke can probably confirm, but I think by 1977 those would have the 4 valve heads. What's the power rating and are they 4-71 or 6-71s?

 

[PierreR]

Lepke can probably confirm, but I think by 1977 those would have the 4 valve heads. What's the power rating and are they 4-71 or 6-71s?

Engines are 4-53's, power rating is 112hp @ 2,500 rpm with N-45 injectors.

 

[Mako]

Thanks for all the input. I got this info across to my buddy for his consideration to purchase.

 

[Mako]

Engines are 4-53's, power rating is 112hp @ 2,500 rpm with N-45 injectors.

Curious if the engine can be further derated down to about 80hp with even smaller injectors.

 

[tiltrider1]

Curious if the engine can be further derated down to about 80hp with even smaller injectors.

Why? Once you have reached max contiguous HP you can de rate by pulling back the throttle.

 

[PierreR]

Curious if the engine can be further derated down to about 80hp with even smaller injectors.

The answer is yes although I do not know what the result will be on efficiency or mpg. I think it will handle N 30 injectors and I think that would be around 90hp.
If I every run into anyone that is a true expert in Detroit's, I will ask. It would call for a smaller diameter prop but not much.
If I went that way I would probably go to N 40's and use the spare props that are a touch smaller.

 

[Mako]

Smaller injectors, reset the governor to limit rpm, keep the same diameter prop but reduce pitch, operate the injectors now more optimally so they atomize better.

Now you’re loading the prop more fully. Very small increases in fuel efficiency do add up. Depending on your use case and if the engine was overpowered for the application.

 

[PierreR]

Smaller injectors, reset the governor to limit rpm, keep the same diameter prop but reduce pitch, operate the injectors now more optimally so they atomize better.

Now you’re loading the prop more fully. Very small increases in fuel efficiency do add up. Depending on your use case and if the engine was overpowered for the application.

My engine is overpowered for the application. At 7.4 knots I burn 3 gph @ 8 knots I burn 4 gph @ 8.5 I burn 6 gph @9 knots I burn 9 gph and at 9.6 knots I burn 13 gph. Hull speed is 8.25 knots

My boat is full displacement with a D/L of 335 at normal cruise wt.

If you reduce pitch you need more rpm's to get the same speed. The ptich diameter ratio is already at 0.5. Props are 26" x 13" I don't understand where the efficiency comes from.

 

[Lepke]

Smaller injectors limit top end. It's the same as reducing the throttle position. You spend $ hundreds for new injectors to save maybe 5% fuel.

4 valve heads came out some time after 1970 (as I remember) in the quest for more HP. In a natural 671 a 4 valve gives about 1 km better mileage in boats I have run.
4 valve is necessary for above 300 hp.

When I needed above 300hp I bought a 12v71 instead of beating a 671 to death. I used 1, 2, 3, & 4-71s as generator engines. But I had friends with 3 & 4-71s a main engine in salmon trollers. The 3 was especially economical. A 2-71 generator will run for decades and no glazed cylinder problems. Runs at 1200 rpm.
A long time ago I had a 1-71 running a 250v DC generator. You could hand start it.

 

[Captain DJ]

I had twin 4-53 NA with N30 injectors on my Grand Banks 42 Classic built for Robert & Mildred Newton, the founders of American Marine Ltd. on Hull 125 of that very successful 42 classic series of "Trawler Yacht". I had 800 gallons in factory steel tanks 4 total (170 fwd/230 aft x each side) plus I installed a 40" tall day tank with a 40 gallon capacity. With pre-filtered fuel in the day tank and a sight gauge and transfer manifold/timer pump accessible from Aft stateroom I could track fuel consumption more accurately than any other method I have found. Over many years averaged consumption of 1.35 gal/hour/engine at average 1550 rpms and 6.85 knots/ave. Those engines had over 8,000 hrs on them and I would bet they will last double that more if treated fairly.

 

[Wildbill]

We have twin 4-53 Detroit engines in our 1980 Hatteras LRC, they happily growl at 1800 rpm burning 4 gallons per hour at 7.5 knots and have close to 6000 hours on them. They powered us around the loop and back and forth to Maine repeatedly. I wouldn’t have concern about high hours Detroit engines provided they were maintained properly and they had the proper oil. They outperformed most of the newer engines on the loop whom had fault codes issues.