Cummins 6BT5.9M Engine

[Leaforge]

Hello All,
I am considering buying a MB with a 180 HP Cummins 6BT5.9M engine in a 45ft 1998 boat. It has 3000hrs work on the meter, the boat is a little tired but with TLC and a few quid should suit our purpose as we do not propose getting anywhere fast. We are happy with displacement speed, though economy will be important. My question is that this engine appears to have more than one power output notably 220hp. This is a single engine vessel.

• Is the 180hp upgradable to 220hp?
• any idea of likely cost to overhaul engine?
• any known issues?
• 180hp out of a 5.9ltr engine seems inefficent - have I got that completely wrong?

This is a single engine vessel.
Many thanks in advance.

 

[tinkicker0]

Latestarter of this parish does a nice line in refurbished and well fettled marine variant 6BTs and well above 220bhp too.

Why not send him a PM?

You'd be daft not to.

 

[rafiki_]

The engine sounds nicely under stressed to me, and should chug along happily for many years.

 

[Latestarter1]

Not sure why you think 6BT 180 should be inefficent, is the medium continious rating of the 6BT 210, both the same CPL, 742 just a pump tweak rest of hardware was the same, 180 a 2,500 rating 210 2,600, remember these are 40 degree C proper hp ratings, none of your 25 degree C metric hp stuff. Not sure what marime motors you have experience of, but this is certainly no chainsaw motor.

If you were to compare engine as currently rated it would easily match say Perkins Perkins Sabre 225, uprating pump to 210 and you are in a different league from the Perkins 225.

Straight turbocharged engine as simple as wheelbarrow. Has distinction of being the longest production marine engine made. Product was launched in 1986/7 and still in production today, as a Cummins ReCon unit but actually built using new components, to get around US emission regulations. Weakness, just Sherwood raw water pump, however Sherwood M71 a better widgit than bigger 17XX pump.

You are considering re-build at 3,000 hours, the 180 rating is a 3,000 per annum medium continuous engine, please elaborate as to why you are considering rebuild?

IF you really want a recon motor I actally keep a CPL742 on the rack, as it is a popular motor for driving bow thruster on sand dredgers, which have decent 500 hr maintenance but operators like to change out at 15,000 hours and ask me keep a spare on the shelf in the event of an emergency.

Motors will go through two cycles i.e 30,000 hrs without any crank work, then cheaper to purchase brand new genuine Cummins crank than bother re-grinding.

Would be surprised if your motor does require re-build but if you need a CPL 742 just PM can also re-rate pump if you require it.

Good luck

 

[kashurst]

judging by Latestarters reply sounds like you have a cracking engine in your boat that's just about run in. As long as the oil pressure is OK and it runs at correct temperature, give it a really good service and it should last a seriously long time.

Upgrading power output sounds realistic but bear in mind once the boat hits maximum displacement speed (for a 45' boat @ 8 kns), it won't go much faster with more power unless there is enough power to get on the plane. What type of boat is it?

 

[Leaforge]

Hello

Thanks for the very informative posts for which I am very grateful.

I am not considering a rebuild / replacement just looking at worst case senario prior to final bid, as you have guessed marine engines are not my bag, done a few petrol ATV and car engines in my time.

What is the ball park for a full service and replacement of oil, filters etc?

I am asking lame questions as this is a first boat and trying to tick as many boxes as possible, plus would envisage a possible trade up in 2 years time. we are planning to use the boat rather than a weekend retreat in a marina!

Thanks.

 

[Latestarter1]

Hello

Thanks for the very informative posts for which I am very grateful.

I am not considering a rebuild / replacement just looking at worst case senario prior to final bid, as you have guessed marine engines are not my bag, done a few petrol ATV and car engines in my time.

What is the ball park for a full service and replacement of oil, filters etc?

I am asking lame questions as this is a first boat and trying to tick as many boxes as possible, plus would envisage a possible trade up in 2 years time. we are planning to use the boat rather than a weekend retreat in a marina!

Thanks.

6BT is a real simple DIY motor, Fleetguard oil and fuel filters should come to no more than £20 for the two, however at 3,000 hrs I will give you a plan for another trouble free 3,000 hours.

#1 Fit a new raw water pump, Sherwood pump bodies made of cheesecake bronze. You could overhaul pump with kit from ASAP suppies however kit is £190 and your pump body will be showing signs of wear, a new cam is only a short term soloution and the brainless engineer who concluded that it was smart to locate the cam with a stainless steel set screw must have been on drugs. Cam wears exposing screw, which then tears into the impeller into perfect size lumps to block heat exchanger tubes. Best solution, fit a new raw water pump, ASAP Supplies for a Sherwood M71 or I can get you a Sherwood clone from the U.S. with body manufactured from proper Naval spec bronze, takes standard Sherwood impeller and incorporates a degree of intellegence in the design and no more expensive.

#2 Remove tubular heat exchanger, take off end caps, you may find a junkyard inside, bits of zinc as well as impeller parts. Rod out tubes and clean with Rydalyme. Only zinc on this engine is in the heat exchanger, Cummins charge stoopid $$ for the zinc as it comes pressed into the big NPT plug. Go to Zincsmart, they do the brass plug and zinc as separate threaded items you just unscrew the old zinc from the plug when it comes to HX servicing. I keep SenDure HX end cap gaskets if you need them.

#3 Have the belt guard off the front of the engine and check bearing on automatic tensioner as well as inspecting the inside of belt for cracks.

Once you have completed the above just go out and enjoy the vessel.

P.S. I have manual on PDF if you want to PM me

 

[PCUK]

I've got a brand new genuine Cummins part, Sherwood pump for a 6BT M2. Complete with drive gear and ready to fit. Obviously it will have all the problems Latestarter mentioned (and that I wasn't previously aware of). Perhaps LS could suggest what the right price would be for this! (If you want it). Considering the retail price I thought about £400 but I'm sure LS will put me right,

 

[Latestarter1]

I've got a brand new genuine Cummins part, Sherwood pump for a 6BT M2. Complete with drive gear and ready to fit. Obviously it will have all the problems Latestarter mentioned (and that I wasn't previously aware of). Perhaps LS could suggest what the right price would be for this! (If you want it). Considering the retail price I thought about £400 but I'm sure LS will put me right,

Yes but it will still be good for another 3,000 hrs at least...........

 

[benjenbav]

I have a pair of 6BT engines in my boat. Latestarter1 has given me some great advice on them on here and although I am no expert I have found them to be fantastic engines. Over the five years I have owned this boat all I have had to have done is replace consumables. I had an oil analysis done a month or so ago and everything was sparkly clean.

 

[Latestarter1]

I have a pair of 6BT engines in my boat. Latestarter1 has given me some great advice on them on here and although I am no expert I have found them to be fantastic engines. Over the five years I have owned this boat all I have had to have done is replace consumables. I had an oil analysis done a month or so ago and everything was sparkly clean.

When it comes to Cummins stuff I tend to be super critical, people never encounter 1/10th of what I see, only calls I enjoy are those from people who just want to tell me how this or that is performing and that stems from observing a few basic rules and getting it right first time.

As to your Cummins Thornycroft motors you may have Jabsco pumps, Thornycroft had Cleghorn Waring do a bespoke Jabsco pump set up, sadly complete pumps no longer available, but spares all standard Jabsco stuff on the shelf.