CAT 3126b

O

Ozzie-iv

New Member
Mar 27, 2007
289
Bilgola, NSW, Australia
Boat Info
Riviera 4700 sy
Riviera 37
Sea ray 400db
Engines
CAT C9 575hp
Diesel 6bta
Mercruisers 8.1s
Hi All,

wondering if I can get some info or your thoughts on a pair of CAT 3126b 450hp 1000hrs

This is for a buddy of mine who is looking at purchasing his first boat (Riviera 43) This boat is
a 2002 model LOA is around 48ft beam 16ft.

The b series I understand are the electronic version.

He knows that he should take some oil samples but was interested in any physical signs he should look for

thanks

Ozzie
 
I would definitely get some oil samples, and put a Cat guy on the boat and do a compression test, some say diesels need rebuilt after 1500 hours some say 10000 hours, alot depends on the PO's maintanance. one big killer on a diesel engine that kills the life is the cool down time. guys will run them hard, pull them into the dock and turn them off, the important thing to remember are the turbos will hit 1000 degrees along with the exhaust manifolds, if you will notice on any turbo the oil line going in is small and the return line is twice the size so the oil does not restrict on exit. what happens is a guy will run hard and turn the engine off and the turbo will still be 1000 degrees and the oil will sit in the turbo and break down. you have to cool these engines on return for at least 5 minutes to get them to a normal temperature, yes they are designed to run at these high temps but cool down is a must.
its a tough call by mere outside appearance, one thing you can do is on his own is pull the breather and notice any blow by other than that its a roll of the dice, but on a boat that size I would definitely get a Cat guy on there and let him evaluate the condition and wouldnt purchase based on appearance...that is unless they look like sht and they werent taken care of. But a key point is interviewing the owner and asking alot of questions, looking at his maintanance records, did you cool the engines, who serviced them, how often....things to that nature
 
I have the same engines, I've run them for 3 years so far no big problem, They are electronic, a Cat survey would be the way to go, Very easy, they hook up a computer to the engine can tell everything about the engine, how it was run etc. 1 possible problem area are the aftercoolers, Cat changed the design, so depending on the year if they are before the change you can no longer get the tube bundle should they devolpe a leak. Makes for an expensive repair. But I have had no problems, Smoke free, Run great. I have about 600 hours on mine. Bob
 
Caterpillar has a proprietary test to measure cylinder blow by that is far more cost effective than a compressions test but yields the same result....i.e. cylinder wear. Coupled with a fluid analysis, a Cat technician can do a very definitive engine survey in less than a day. The last one we had done was on a pair of 3116's and cost less than $1000 which is real cheap insurance for this much of a purchase.

Caterpillars are generally very clean engines so the engine room should be free of oil or antifreeze leaks. Any leak indicates a problem.

Look for signs that the valve covers have been removed. THe 3126 has a required overhead maintenance at 250 hours so the valve covers should have been removed at least once in the 1000 hour engines.

Observe what brand of oil and fuel filters the previous owner has used........Caterpillar filters are far superior to aftermarket brands........and are usually cheaper to boot. Aftermarket brands indicates short cuts or service done by someone who doesn't know Cat engines.

Although you did not ask about the boat, if this a first boat for the buyer, be sure there is a dealer for that brand close by since this level of boat brings with it multiple complex systems that all have learning curves that can be intimidating.

Look for surface rust on the engines. Any visible rust indicates an owner who is lax on maintenance.
 
All of you that have the 3126b what temperature does your engines show when cruising at around 2200rpm

just went for a run on a boat with temp showing 93 deg c ( i think that is around 199f)

your input will be much appreciated


regards

Ozzie
 
FWIW: The OEM 3126B coolant regulators specs are "Completely open temperature ... 98 °C (208 °F)"

Did your Bud buy, or are you guys still lookin?
 
Hi all,

no my buddy still hasn't purchased..The boat is being hauled out for the surveyo to have a look at this week. Diesel mechanic to have a look at well.

I went with him to have a look at the boat Yesterday (Saturday our time)1.5 hr flight
and went for a run on the boat The guy didn't want to take it above 2300 rpm (19 kots) saying this was what he likes to cruise at.. we were in a bay area which is shallow and reasonably narrow so I wasn't going to argue.

I always worry when I see engines that have had painting done to them ( and over spray has gone over the hose/tubes/wiring and items which are part of the boats plumbing (are they hiding something?? I did notice that the coollant return resevior for one of the engines was empty.

But overall the boat looked good

Ozzie
 
I dont believe the paint is hiding anything, its good maintenance. However the not wanting to come up to cruise speed or wot would worry me.
 
For what it is worth, when I bought my boat in Oct 2007, the engines had been very recently sprayed, and what a b****y awful job someone had done of it. I even found the empty spray cans in the bilge storage boxes. It nearly put me off buying the boat, partly the look of it, (I would rather they looked used but were original and clean) and partly because I was wondering what was being hidden.

In spite of the repaint, I did make a very lowball offer on the boat, it was at first rejected out of hand, and then accepted two days later.

350 hours and two seasons later, engines are great, so far no problems at all. Just dumb in my opinion to paint engines at all, especially when fully plumbed and in situ.

Graham.
 
Repainting is a big +, not a negative (unless it looks like an 8 year old did it!).
A couple of times a year I wire brush any surface rust, use a rust converter, and re-paint. In fact- it's a part of regular maintenance and is specifically covered in the CAT manual.

I agree that not allowing to run at WOT could be indicative of a problem that he's trying to hide. Really- not much difference in speed between cruise and WOT with a diesel, maybe 5-7 knots? Big deal...

The fact is that running WOT for several minutes- without overheating- is a bonafide test of the engine's condition and that of the cooling system. I'm sure the surveyor will insist on it at sea trial (Hopefully, the "joy ride" was not the actual sea trial without the tech aboard).

Good luck.
 
ok Back again,

for your reference and hopefully you may comment..

This boat is 35500lb 48ft loa and 15ft 8" wide fuel 500gallons cap 3126b 450bhp

here are some of the numbers for the starboard engine port number vary only slightly

rpm Oil Pressure Mnifold temp turbo boost fuel rate
2756 - 252kpa - 43c - 97c - 252kpa - 95ltr each engine -22.4kts
2505 - 272kpa - 39c - 95c - 214kpa - 78ltr - 20.2kts
2431 - 284kpa - 37c - 94c - 196kpa - 73ltr
2237 - 316kpa - 34c - 88c - 148kpa - 60ltr
1250 - 224kpa - 33c - 88c - 10kpa - 14ltr -(after wot) 10.2kts sog

bottom dirty, nearly full fuel, full water, 2 adults (fat no I mean big no I mean heavy)

props 25x27.5(pitch) 4 blade
 
Last edited:
FWIW:I randomly looked at a 3126B 450hp performance specs. Boost pressure @ 450 hp is 260.0 kpa. While burning 24.4 gal/hr. @2800 rpm. I’m havin a hard time rite now with the gal/hr vs. ltr/hr. But it sure looks like there making rated power.

Now I’m assuming this was at WOT. So only turning 2756 means there lugging but not bad. Not worth screwing with. That dirty bottom most likely is really dragging her down.

What was used as a tool to gather this data?
 
these numbers were coming from the cat display monitors photos were taken and then sent to me from my friend

divide the litres by 3.8 then you will get gallons

The only thing that concerns me is that she reached only 22.4 knots. I know on my boat that when I start to open the throttle and let it run at a certain revs it takes a while to get a steady reading from the GPS (I mean not instant) . There could have been a current as the area does have quite a bit of tidal flow

Ozzie
 
You must log in or register to reply here.

Forum statistics

Threads
113,196
Messages
1,428,298
Members
61,103
Latest member
Navymustng
Back
Top