4BT and "Tonys Tips" coolant upgrades

[Francis Valerio]

I have twin 4BT in my Bertram 28.  I am very happy with the set up for my recreational activities.  Good on fuel and pretty dirt simple.  Last september I unfortunately had catastrophic failure when the rear (#4) exhaust valve disintegrated and the rest is history.

Now, I have new block and new cylinder head new pistons etc….

After all this work (doin myself) I want to be sure that I make the colling system as good as I can and would like to implement the upgrades that are on Tony suggested on the old 6BT applications.

My engine are 1988 vintage and think I could benefit and at the very least I dont think any could hurt.

For Turbo I got a 1″ Banjo and am gonna plug the rear head fitting and instead add a billet aluminum expansion plug kit and drill and tap a 3/4 NPT hole and then add a 3/4″ by 1″ barb to mate with the banjo on turbo.

That leaves me with the connection on the side front at the coolant inlet elbow that connects with the exhaust manifold (both are 1/2″ NPT now). The exhaust manifold on the 4BT has no threaded hole on the side like the 6BT. Cummins makes this connection via the  “water transfer connection” part #3904971 that is bolted to the top of the exhaust manifold.   The threaded connection on part #3904971 is only 1/2NPT as well as where it leads to on the aluminum inlet elbow. I was considering drilling and then retapping both of these parts to 3/4″ NPT to open them up a bit. There is def enough “meat” on the inlet elbow and would be simple to drill and tap.  Not so sure on the cast steel part 390497 though.  I do think it is doable but looking for some input.

What do you think?

I only had 100 hrs on the rebuild and then dropped a #4 exhaust valve that took out the block and the head. Just want to do all I can to make it better.

Frank

Massapequa Park, NY

 

Topic

[Shannon Ritzert]

I thought about manufacturing some legs from the stinger, and mounting a tank like that on the legs.  I like how you brought yours away from the bulkhead.  Thanks for the picture, that gets the old gears turning in the brain.

[Francis Valerio]

Here is my remote tank that I am using now.

1 user thanked author for this post.

Rob Schepis

[Shannon Ritzert]

That was my thoughts, to have tanks  made.  I really wanted to mount them on brackets on the engine.  as you know in that Bertram, there’s not a lot of space.  There’s zero space on my bulkhead without major re-wiring.  Thanks for the quick reply!  I will try and figure out brackets

[Francis Valerio]

shannon

My expansion tanks are “NOT” mounted to the engines.  They are mounted to the bulkhead wall but can be remotely mounted anywhere you want but they (the radiator cap) must be slightly higher than the engines otherwise coolant will leak when you open the cap…

My remote tanks are a pair that I picked up on ebay and were for qsb engines but I used them anyway and they hold quite a bit of coolant.  Prob more than necessary but the price was right and they are configured in a good way as they dont take up too much space.

It is just basically a reservoir that holds the coolant and circulates it a bit..you could prob have one made up by a welder but you need to copy the size of the orifices of the hose fittings…it is not a terribly complicated design

[Shannon Ritzert]

I am finally about to go through the same process on my 4bt’s.  I am building new motor boxes over the winter to achieve more space.  I am searching for the expansion tanks, and the brackets for the tanks for the 6bt 210 with no avail.  I even ordered the 6bt parts catalog, and the only thing in it is a keel cooling tank.  Did you build your own brackets for the tanks?  

[Francis Valerio]

Here are the performance numbers after logging some hours.

18.7 mph = 16.24 knots @ 2400 RPM low cruise 10GPH (total consumption)
21.2 mph = 18.42 knots @ 2600 RPM high cruise 13GPH (total consumption)
23.2 mph = 20.16 knots @ 2800 RPM
24.2 mph = 21.03 knots @ 2975 RPM WOT

Not bad, she is no speed boat but will get from point A to point B pretty efficiently.

She also get her RPM easily. On a recent trip (a very short trip) to a local cove we were def overloaded (weightwise) and she was still able to make over 2800rpm

This is in my 1971 28 Bertram. (the early boats had lots of fiberglass I believe and may be heavier than later models)

4BT 150’s are doable in this application and their simplicity makes a nice choice. Diesels in the 200HP range would def be more of a target for that solid 20-22 knot cruise. I am more of a solid 17-18 knot cruise.
Thanks again for all the replies and hopefully this thread can be useful for others.

Frank V

[Tony Athens]

Seems to me you have got your your 4BT set up 100% right.. It’s close to impossible to break or wear out that engine if you do not grossly overheat it or feed the turbo salt water.. Other that that, a 100% bullet proof diesel that only costs a few buck a year to maintain…………………..To put things in perspective, it shares the same sized rods & bearings, main bearings, piston size, valve size, etc etc etc. as a QSB 5.9 480..

No wonder it’s close to impossible the break it mechanically….

Tony

[Rob Schepis]

Nice rewards for a job well done – you earned every bit of that…

[Francis Valerio]

Resurrecting an older thread here,

I bought new props 17X16 no cup

The old props were reworked to 17.5X17 and I was still a little overpropped.

I am very happy to report that on a quick test run today when I splashed for this season I made 3000RPMS easily and that is with an almost full tank (130 gallons in a 157g tank)
It was just me and 1 friend on board. It felt great how the engines really pulled all thru the powerband after 2000rpms all the way up to WOT and a max RPM of 3000.
I think with the boat loaded on a normal trip we will be over 2900 easily.

Also the engines stayed right at 160F with the smx thermostats

It makes me feel good because there is NO QUESTION that I am propped correctly. I am probably slightly UNDERPROPPED but there is such a fine line that I think I will leave it as it is.

I will post performance numbers after I get out a few times but I think we are good. I am still cruising at about 17 knots sipping fuel and can cruise at 20 knots at about 2500rpm give or take.

[Francis Valerio]

Additional upgrades

Tony

In the past you have always recommended to upgrade the “coolant plumbing” on the 4BT and early 6BT series engines.

I have upgraded the plumbing to the larger fittings and hoses, I have also installed a real expansion tank, 160F Thermostat.

Is there anything else to upgrade or tweak to maximize reliability? (I think you once said… “and a few other things…”)

As long as propped correctly what do you think is a good rpm for cruise.
I am liking my boats planing and handling @ 2500RPMS now @~20 knots

Is that running too hard or could I even goto 2600???

[Tony Athens]

Not sure how the “spitter hose” are put together, but if can put something inside the hose with a 3/32″ `- 1/8″ ID hole in it, that’s all it takes…

[Francis Valerio]

Thank You Tony and you have a good eye, I think the hose is for sure greater than 1/8″ ID.

I can restrict the passage in the fitting possibly? Down to 1/8″ ID and still use my existing hose???

The rear plate is a billet freeze plug plate and it cam with a 1/2″ threaded hole but I drilled it out and retapped to 3/4″ and added a 1″ hose fitting to match the other upgrades. So far so good with it.

[Tony Athens]

You done a GOOD JOB ! I especially like the custom plate at the rear of the block..

Only caution, but I cannot tell for sure– Your spitters that go the the X-Tank..The hose look big? Be sure the flow is restricted –1/8″ ID max is what you want someplace on a fitting or the like.. If you “spit too much” your temps will run high as this coolant by-passes the heat -X.. They are they for de-airing the system only, and not for cooling.. Al lot of mechanics, supposedly “in the know”, do not know this..

[Francis Valerio]

Pics of plumbing upgrades for a 4BT

Here are some pics of the upgrades I did from Tony’s recommendations. I removed the undersized coolant expansion tank that are standard on a 4BT 150 and 6BT 210 and plumbed in the later model coolant hose to take its place. I got this from SBMAR a while back. I then upgraded the fittings to 1″ that utilize 3/4 thread to replace the narrower fittings that come stock.
A cummins mechanic also recommended to utilize the rear freeze plug on the block to allow better flow of coolant on the rear to better cool rear cylinder. The 4BT has the turbo mounted very close to this location. I think this should allow better circulation. I am also using a 165 Thermostat. I made my own coolant expansion tank as well. I piped a coolant temperature alarm in the now empty fitting at rear of the head. That fitting went to the turbo which now connects with the freeze plug adapter fitting.

Tony, is this satisfactory and if so what do you think a safe cruise RPM could be with these mods. I posted my temperature gauge pics in previous post on this thread and the “modified engine” is maintaining approx 170F on short runs of WOT.

I am still dialing in the props but they are close to optimal (~100-125 rpms off where I want to be)

[Francis Valerio]

Return lines check?

I have now put about 30 hours of operation this month (June 2020) on my 4BT 150’s. Today I ran all day and no problems. I have approx 110 gallons of fuel (157g tank) and was able to attain 2790 rpms (both) with 2 adults and 2 children and fishing gear and cooler.

I did have props worked for this season but I think I am still “slightly” over propped. I was hoping to achieve closer to 2900 and was able to get close on a test run last month. Have not been able to since.

I think I am getting all they can muster and am leaning towards “props”. I have gone thru all the checks from the Tips Section. I do not know how to check the flow in the “Return Lines”? Any suggestions?

Here is a few pics of my coolant temperature readings. Port engine is with regular cooling system and the Starboard engine is utilizing the suggestions from Tony’s Tips. These reading were after running all day and while cruising at 2250 rpms @ 16 knots. I usually cruise at 2400 rpms @ 18 knots. I think the tips are working well and pics are earlier in this thread.

[Francis Valerio]

That was on the Tach.

The tach is a twinscan type and I have the magnetic pickup in the bellhousing.

I only checked the RPM with the strobe upto 1200rpm. (I dont like putting my head down there with the strobe with the engine racing so high). I will do it if you think I need to…

[Tony Athens]

Was that 3200 your tach or a strobe?

[Francis Valerio]

I was getting 3200 rpm at the dock, I have adjusted the throttle screw to stop at 3080rpm.

I will seatest tomorrow

[Francis Valerio]

I know for sure at dock I get “over” 3000rpm in neutral. It is possible I am at or over 3100.

I need to check again, I dont like to keep the engine at WOT at the dock. I guess it is ok for a short time. I will try tomorrow and see where it is at.

[Tony Athens]

Check your tachs under no-load at the dock and write down the numbers..Don’t worry about using a strobe.. Assume your CAV pumps are set correctly that will limit the actual max RPM’s to 3050 -ish ………….. So , what ever they say, use that as your standard (3050 RPM) ..

If you get to within 150 of what ever that RPM is, then you are getting all they have to offer.. ( example= 2950 on your tachs no load, would mean you are probably making a real 2900) ..

Make sense?

[Author]

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