Mercruiser 1.7 Diesel in a 6m Rib

[Nauti Buoy]

Does anyone have any info regarding Mercruiser Diesel's and whether or not they are any good, I have seen a 6m Rib with a 1.7 Mercruiser Diesel and was after some feedback if possible before saying yes to it.

[Louise]

Andre teams his Parkers (which are 6.5m I think) with this engine and rates them very highly, I believe. I'm sure he'll be able to give you lots of info.

What make is the RIB you are looking at?

Edit: Oops. Sorry, Dave, forgot you had one too! (See below.)

[Nauti Buoy]

Originally Posted by Louise

What make is the RIB you are looking at?

Hi Louise, I am not allowed to say at the moment (as much as I am itching to do so) and will put pics up as soon as/if the deal is done. I am going to be used as a Guinea Pig and getting the rib at a 1/4 of the price as it will be used as a Demo Rib. It has been Sea Trialed just having a few minor adjustments then I will be allowed to open my mouth. Sorry very frustrating for me not to say anymore.

[simmons0]

go for it!
Its more than enough to pull a skier
9 litres an hour fuel consumption

and the big one, I get 45knots from it.

[Nauti Buoy]

Originally Posted by simmons0

go for it!
Its more than enough to pull a skier
9 litres an hour fuel consumption

and the big one, I get 45knots from it.

Well if i can get that I will be well happy have you had a trouble out of yours? or things I should be aware about?

[Andre]

Originally Posted by simmons0

go for it!
Its more than enough to pull a skier
9 litres an hour fuel consumption

and the big one, I get 45knots from it.

Hi David and Harry

Have you been away cos not seen any posts for some time. Been doing anything exciting, like ribbing. How is Tombouy?


Nauti Bouy, a lot has been said about the Mercruiser 1.7 so suggest you do a search and happy reading cos the engine in question is just GREAT

Should you need any further info just fire away . I am on my second Parker 630 with the Mercruiser 1.7 so have got to know it pretty well.
in short it is ideal for a 6-6.5 mtr cruising rib

Forgot to mention that we have just fitted a twin installation on a Parker 750 Baltic rib

[Nauti Buoy]

Thanks a lot Andre, I will no doubt be contacting you with any questions.

[Searider]

"and the big one, I get 45knots from it."

Really?

I tried a 6.5m (not a Solent) with a Merc 1.7 and managed only about 35kts. - has almost decided me that I need to stick with outboards! If the Solent can make 45 kts with the diesel then I need to speak with Lee.
I'm not sure I believe 45 knots though?

Duncan

[John Kennett]

Originally Posted by Searider

I'm not sure I believe 45 knots though?

No offence to simmons0, but I don't believe it either! I know that the Solent RIB hull is generally pretty quick, but 45 knots from a 6.5 metre boat with just 120hp does seem unlikely . . .

John

[Colin F]

Originally Posted by John Kennett

No offence to simmons0, but I don't believe it either! I know that the Solent RIB hull is generally pretty quick, but 45 knots from a 6.5 metre boat with just 120hp does seem unlikely . . .

John

simmons0 boat is a 6m, not a 6.5 for what that is worth. Personally i decided to go for a few more horses (sadly and quite a few more £££££) so i had some spare. you pays your money and makes your choice

i'll let people know the performance of mine when it arrives nov/dec

colin

[Nauti Buoy]

Talking with Andre and he reckons he gets a maximum speed of 33 Knotts from his 6.3m, with a comfortable cruising speed of 26/28 knotts, which seems realistic I guess. Will let you all know when it eventually gets on the water again.

[John Kennett]

Originally Posted by ribnwheels

simmons0 boat is a 6m, not a 6.5 for what that is worth.

My mistake! With a relatively low powered rig that half a metre might make quite a difference I suppose.

There seems to be a general and widespread tendency for people to be rather generous with their top speed assessments. I still think that 45 knots is optimistic in this case, but would be happy to be proved wrong.!

John

[Dave B]

I have the Mercruiser 120 Hp in my Prosport 6.5 Mt

It will cruise at 25-28 Knots at 3300 RPM dependant on the sea conditions.
Top Speed is around 36 Knots at 4200 RPM

This is with a 23” prop and the leg trimmed out correctly

Incidentally the RIB can make 20 Knots in to a head sea of around 2 Mts without backing off

Fuel used is 3 Gallons per hour as expected, A good power unit in my opinion.

Alan Priddy might get 40+ Knots down one of his big swells around Greenland but I don’t wish to try it!!!!!!! ***By Big Swells I do mean the sea type***

[Dirk Diggler]

Originally Posted by Dave B

Alan Priddy might get 40+ Knots down one of his big swells

In his dreams!

[brucehawsker]

Is there a rule of thumb as to how fuel consumption rises with length? If someone gets 1.3Nm per litre with a 150 Opti in a 6m Rib, what would the similar figure at similar crusing speeds be for a 6.5m, a 7m and an 8.5m?

Does consumption differ significantly due to hull design?

What are the most important factors?

RPM
Speed
Weight
Length
Hull
Phase of moon

It should surely be possible to come up with some simple guidelines here?

Bruce

[DM]

Originally Posted by brucehawsker

Phase of moon

The three different makes of 6 meterish ribs that I've driven this season, fitted with the 1.7 mercruiser, have only managed 32knots and that includes the Pro sport.

Maybe they go faster when there's a full moon.

DM

[Dave B]

As I said in my last post with a 23” prop my Prosport will make 36 Knots dependant on the sea conditions,. I have tried the same rib but with a 21” prop and that was not very good but with no GPS or log I am unable to tell the exact speed.

Using a chart plotter and a Garmin 126 (to determine Speed) out on a flat calm sea with little or no wind and two crew the Prosport will make 36 Knots.

Just for interest my last rib was a 5 Mt Humber Attaque with a 50 Hp Honda. Flat out and I mean flat out I was paced at 32.5 knots.

With a 23” prop the Mercruiser will not rev out to 4500 but is within the limits set by the manufacturer.

No need for a full moon, but it does help on a night passage.

[Andre]

Originally Posted by davidmanning

The three different makes of 6 meterish ribs that I've driven this season, fitted with the 1.7 mercruiser, have only managed 32knots and that includes the Pro sport.

Maybe they go faster when there's a full moon.

DM

I go along with David 32/33 knots is the very max speed and hv tried the s/steel 23" prop (Laser of course) and the s/steel 21" . Kept the 21" cos has better acceleration

[simmons0]

If your around the solent for the charity cruise ill show you 40 knots+ for yourself.
Racing a friends boat in small chop with 3 people and 80 littres of diesel we hit 43knots and on the boats maiden voyage up the river from fareham hit 47.7knots with barely any fuel, a few knots of tide and Kevin from solent ribs driving.

This is with a 23inch Ali prop reving at 4500-4600 rpm.

edit: I did have a photo of 43knots on the gps somewhere. Ill see what i can do.

[Jono]

The Shakespeare 600 space cruiser (advertised on Boatmad..go on treat yer self, you know you want to!) with this engine in recorded 33 Knts (GPS average for two way run) at 4200 RPM. 1.4 tonnes displacement, 2 "lardies" on board swinging a 21" x 14" 3 blade alloy prop.Trimmed for speed...

...but Ooo! what a hoot! If I wanted a hardboat, this would be it... smooth, smooth, smooth... and the wonders of diesel economy It's currently at Pwllheli if any one fancies a demo...


actually, I shouldn't have said "two" lardies, sorry Jo...