Humber 6.3 & Mercruiser 120 tdi

Jono Garton · 20 September 2006, 19:16

Hi

Anyone been in a Humber 6.3 Ocean Pro and Mercruiser 120hp Diesel??

If so what was top end speed and pick up like?

Any pics?

Jono

simmons0 · 20 September 2006, 19:55

Mike C has one.

Few pics here: http://rib.net/forum/showthread.php?t=2264&page=1&pp=10

I remember him saying 34/35 knots top speed, but he has been playing with different props since then.

Think Andre got at least 36kts out of his last 6.3 and we get 38/39kts but with a 23" prop. They are both, or at least were using 21".

Harry

Paul Beaurain · 22 September 2006, 20:21

Hello Jono

Jon Adlard has one - for a couple of years now.
He knows it inside out as he put the engine in himself.
He cruises extensively.
I believe in summary the early engines had some issues. these have been resolved as production/development continued.
If buying used knowing which spec of engine would be critical.

I'm not sure how often he reads/posts on the forum.

pm me if you need his number

Paul

John Kennett · 22 September 2006, 20:46

Quote:

Originally Posted by Jono Garton

Anyone been in a Humber 6.3 Ocean Pro and Mercruiser 120hp Diesel??

If so what was top end speed and pick up like?

I haven't tried the Humber, but I have driven Andre's Parker 630 with that engine if that's any help.

It's a very competent and economical boat for leisurely cruising, but it lacks the grin factor that you'd normally expect from a RIB.

There isn't much pickup, to the extent that I found it challenging to drive in difficult conditions. You can't simply crack the throttle open and pick the bow up like you would with an outboard, and there were several times when I was stuck on the back of a wave at full throttle, just riding the wave.

Probably make a good training boat though.

John

IanE · 23 September 2006, 22:02

although I haven't done any checking....

Also I believe my engine's one of the early ones! serial nos OMxxxxx

There's a yahoo forum about the engine issues.

The only comments I would make are

JK is spot on re the Parker.

My engine overheats when running at full RPM (over approx 4100)

I'm going to investigate this fullly over the winter.

When buying the Parker, I also looked at a Humber -they were offering

Mercruiser or VOLVO -about 2 -2.5k more. Again I didn't fully research the

weight etc.

Its fine for what I want ... a steady 20-24kts at 4000 rpm fully loaded with a little in reserve. I believe the setup on Andre's latest 630 gave a few kts extra

HTH

Ian

Jono Garton · 23 September 2006, 22:58

cheers for the input guys

alt · 23 September 2006, 23:15

Are you talking about the Mercruiser 1.7DTI? I have this engine in my Panther 19. I would really appreciate if you could forward a link to the Yahoo forum. I have (touch wood) not had any problems with this engine after 100hours of use (Changed the oil twice @ 50 hours, changing the gearoil on the alpha one leg tomorrow). A very well educated friend commented 'You run her at a very high RPM' when taking a spin in the boat one day. I generally cruise at about 3600RPM @ 25knts, sometimes up as far as 4000RPM @ 30knts. I know the engine is stated WOT between 4000 - 4500RPM, is it safe to be running her at 3600 - 4000RPM?

Quote:

Originally Posted by IanE

although I haven't done any checking....

Also I believe my engine's one of the early ones! serial nos OMxxxxx

There's a yahoo forum about the engine issues.

The only comments I would make are

JK is spot on re the Parker.

My engine overheats when running at full RPM (over approx 4100)

I'm going to investigate this fullly over the winter.

When buying the Parker, I also looked at a Humber -they were offering

Mercruiser or VOLVO -about 2 -2.5k more. Again I didn't fully research the

weight etc.

Its fine for what I want ... a steady 20-24kts at 4000 rpm fully loaded with a little in reserve. I believe the setup on Andre's latest 630 gave a few kts extra

HTH

Ian

simmons0 · 24 September 2006, 02:09

We tend to stick to 3800rpm as a fast cruise but will cruise it at 4000rpm when needs must!

IanE · 24 September 2006, 09:31

here

jwalker · 24 September 2006, 12:38

Personally, I wouldn't give sustained running at more than 10% less than WOT.

Somewhere, there will be torque graphs, service load graphs, fuel consumpion graphs plotted against these and exhaust temp against load graphs . It's probable there will be a sweet spot and it might be worth knowing. For my Volvo, 2800rpm is a good place to be and that is 20% below full throttle.

There will be a 'Duty Rating' for your motor. Mine is categorised as Pleasure Duty and I'd be surprised if the Mercruiser is different.

I've just looked up the Volvo manual under the heading;

Marine Propulsion Engine Rating Definitions:
Rating 5. Pleasure duty.

This power rating is intended for pleasure craft applications only, which presumes operation by the owner for his/her recreation, running hours less than 300h per year.

Full power could be utilised for a maximum of 1h per 12h operation period.

Between full load operation periods, engine speed should be reduced at least 10% from the obtained full load engine speed.

There is a; Please note, The rating on each product states the toughest application allowed.

I'm not sure whether this is Volvo's own rating or a general standard. It gives the impression it is general.

The manual goes on to say that an engine used for tougher service than that recommended will invalidate its warranty.

IanE · 24 September 2006, 13:22

here

jwalker · 24 September 2006, 14:07

Excellent. 3600 cruising is the most economical. Above 3800 and it begins to drink twice as much fuel. Unfortunately, at that speed you've only got about 65hp. At a guess, say, in a medium loaded 6mtr boat 20 - 22kts.

Cummins pleasure use is a little more strict on max rpm use but a little more lenient on cruise rpm.

Andre · 25 September 2006, 19:29

Quote:

Originally Posted by jwalker

Excellent. 3600 cruising is the most economical. Above 3800 and it begins to drink twice as much fuel. Unfortunately, at that speed you've only got about 65hp. At a guess, say, in a medium loaded 6mtr boat 20 - 22kts.

Cummins pleasure use is a little more strict on max rpm use but a little more lenient on cruise rpm.

Don't agree when talking about a 6.0- 6.3 mtr rib and WOT. Ask Mike C he's had one for a few years

jwalker · 26 September 2006, 00:22

But, Andre, I wasn't talking about WOT. The curve to look at is the one that gives the power at the correct propeller loading. Cummins use the exponent of 2.7.

I wasn't very clear when I said twice the fuel. If you look at the difference in fuel consumption for each 200rpm rise in engine speed you'll see that after about 3700-3800 the motor consumes about twice what it was consuming before for each 200 rpm rise. 3600rpm would seem to be about the sweet spot for cruising fuel consumption. These figues will only apply if the prop fitted allows the engine to rev to 4400rpm with the load it is carrying...that's when the prop load will match the exp.2.7 curve.

Of course, it's possible to pitch up the prop and open the throttle more and cruise at a higher speed for the same revs but then you are using the engine above the loading of the pleasure rating.