Wanted - Diesel inboard rib

[Intertidal]

Hi all,
New to the forum - looking for recommendations on which 6.5-7.0 diesel rib people would advise purchasing. Priorities are;

1 Reliability
2. Sea keeping
2. Economy

Ideally would cruise @ 26kn loaded.

I am a cash buyer ready to go so if anyone has something that might fit the bill please do let me know.
Many thanks

[jakew009]

Originally Posted by Intertidal

Hi all,
New to the forum - looking for recommendations on which 6.5-7.0 diesel rib people would advise purchasing. Priorities are;

1 Reliability
2. Sea keeping
2. Economy

Ideally would cruise @ 26kn loaded.

I am a cash buyer ready to go so if anyone has something that might fit the bill please do let me know.
Many thanks

Appreciate this doesn't really answer the question but is this your first boat and why do you want a diesel?

I thought the same as you before buying my boat having spent my life around diesel engines, but now I am more learned, I have realised that diesels are generally just a massive pain in the ass.

Unless you are going to be doing a thousand plus hours a year I very much doubt the fuel saving on a diesel will cover the increased repairs / maintenance / hassle.

Once red diesel goes (soon?) the outlook looks even more bleak.

The only benefit is that diesel is available at more marinas than petrol, but even that may change if they have to start having red tanks and white tanks...

[Intertidal]

Thanks for the response. This will be first rib not first boat and does need to be diesel inboard. Some interesting points you have made though, thank you.

[mikehhogg]

diesel inboard is more economical by far, diesel is more efficient and produces more real power at the prop or jet etc. I totally disagree with the cost of maintainance compared with petrol outboards. ,no highly flammable expolsive mixtures on board. no troublesome damp electrics,the list goes on.

[Intertidal]

I have seen a couple of 6.5 - 7.0 ribs running the mercruiser 1.7tdi and Volvo 130. Curious as to how they perform with a load whilst cruising? I’m not interested in flat out speed rather a safe comfortable cruise.

[mikehhogg]

after thirty years of boating I still dont get it. a boat hull had a designed displacement and top speed \power ratio. adding more power is a waste of energy,adding a second engine is madness unless its a backup. I was on a rib recently that had two 150hp petrols hanging off the transom,fuel consumption about 70 ltrs an hour. 70 lts diesel on my rib would do me a week of fishing and diving.Its a no brainer unless your a no brainer

[beamishken]

Originally Posted by Intertidal

I have seen a couple of 6.5 - 7.0 ribs running the mercruiser 1.7tdi and Volvo 130. Curious as to how they perform with a load whilst cruising? I’m not interested in flat out speed rather a safe comfortable cruise.

Avoid the merc 1.7 they aren't a great engine & personally I'd want bigger than 130 for an inboard.
Yanmar 4lh @240hp or yanmar 6lp@315hp would be my first choices there are a lot of yamahs diesel powered boats about which uses the same base toyota 4.2 engine as the 6lp but they stopped production about 10 years ago so some parts are hard to find but a good reliable engine all the same. Volvo Kads were ok but personally
I'd want to avoid volvos later offerings just because they are so dealer dependent although a lot of folk speak highly of the d4 & d6 & later d3's
The petrol/diesel debate will rage on & the loss of red may or may not happen post brexit as it was European driven & our govt didnt want it anyway. I own two diesel powered boats a delta rib & a cruiser & love them both but i can also see the benefits of a lightweight petrol outboard for a rib (which I also own) . Sterndrive is imho the only realistic option for a diesel rib as jets are too power hungry & shafts dont suit, drives can be reliable if well looked after and maintained but can also be a maintenance nightmare too.
There is no right or wrong choice its down to personal preference at the end of the day

[paulbrown22]

Originally Posted by mikehhogg

diesel inboard is more economical by far, diesel is more efficient and produces more real power at the prop or jet etc. I totally disagree with the cost of maintainance compared with petrol outboards. ,no highly flammable expolsive mixtures on board. no troublesome damp electrics,the list goes on.

I do absolutely love my 9m Ribtec with a 315hp Yanmar 6LP, but between the engine and Mercruiser drive, it does take a fair amount of maintenance to keep it up to spec, and that's without any major issues. We certainly spent far less on our previous RIB with a 4 stroke outboard, and that's with me doing most of the work on the Ribtec.

Depending on where you are located, diesel can be far more accessible on the water, which I see as a big plus when extended cruising. Fuel economy, if you're talking similar power and speed - I'm not sure there's that much in it between a diesel and modern 4 stroke from previous figures seen on Ribnet, I thought most people were claiming around 1l/NM from diesel and modern (single) petrols at a cruising speed, give or take a bit? Obviously, if you have twin outboards, an old 2 stroke, and/or you run the boat faster, there can be a vast difference.

[Searider]

There's not a lot of choice of boats and engines at that size.

120hp Mercruiser on an Alpha drive. Reputation for the waste gate sticking shut and melting the pistons.

KAD32 170hp Volvo Penta. Good engine but very few RIBS built with these. Would be ideal in a 6.5m.

Yanmar 240hp on a Bravo Drive. Would go very nicely in a 7.5m.

Yanmar 315hp on a Bravo Drive. Good performance in a 7.5m.

Coastline built some 7.0m and 7.5m boats with Volvo D3-160s and they were good.

Scorpion built lots of 8.5m with a variety of Yamaha and Yanmar/Mercruiser combinations. 8.5 Scorpion with a Yanmar 6lp on a Bravo drive is a lively package.

One thing to bear in mind is that the engine takes up space in the rear of the boat. Allow losing 0.5m - 1.5m in comparison with an outboard boat.

I guess it depends on your budget. If you have £50k plus it opens up the options a bit.

OR, at the other end of the market (price wise) there are always a few ex Navy pacific 22s around. Built like tanks, not a lot of space, but diesel and 6.5m.

[Pikey Dave]

My first RIB had an inboard petrol engine, admittedly not a diesel. The maintenance was considerably more than the outboards I’ve subsequently owned. The loss of space was considerable too. Personally I think RIBs are a difficult environment for inboards, but that’s just my personal opinion based on limited experience.

[Philip Hodson]

Inboard makes RIBs look much sleeker & sexier rather than having a great big lump
hanging off the back of the transom

[Pikey Dave]

Originally Posted by Philip Hodson

Inboard makes RIBs look much sleeker & sexier rather than having a great big lump
hanging off the back of the transom

Beauty is in the eye of the beholder [emoji6]

[jakew009]

Originally Posted by Philip Hodson

Inboard makes RIBs look much sleeker & sexier rather than having a great big lump
hanging off the back of the transom

Hmm. I just look at them and think there's no way on earth I'd want to be standing on my head trying to fix anything in that engine bay.

[jakew009]

Originally Posted by mikehhogg

power is a waste of energy,adding a second engine is madness unless its a backup. I was on a rib recently that had two 150hp petrols hanging off the transom,fuel consumption about 70 ltrs an hour. 70 lts diesel on my rib would do me a week of fishing and diving.Its a no brainer unless your a no brainer

A diesel engine will burn around 0.2 litres per HP per hour depending on the model, give or take a couple of litres.

A 4 stroke petrol engine will burn around 0.32 litres an hour per HP, give or take.

That's just the way it is.

So your correct that a diesel boat will use less fuel than a petrol one, but it's hardly 1 hour vs 1 week of boating as you suggest...

[GuyC]

I'm the proud owner of a diesel RIB but I suspect they are a slightly left field choice. I bought mine primarily because of the availability of diesel in the Outer Hebrides.

I'd agree with most of the negatives that are mentioned about inboards although I'd stop short of calling them a pain in the arse and I'm not sure my Pac 22 could be called sleek and sexy.

I'm also not sure that petrol outboards are more dangerous than diesel inboards although they have the potential to be dependent on the user.

Deck space is an issue although you can usefully use the space on the top of the engine cover.

The stern drives seem to require more TLC than the engines. When the gearbox is built into the stern drive, there seems to be a few issues with the gearboxes not liking the torque the engines produce. Pac 22's have an engine mounted gearbox with a shaft leading to the stern drive. If money were less of an object I'd go this route again but with a new Konrad stern drive. Again it impacts on deck space particularly as the engine ends up being further forwards.

They tend to weigh more as well.

I like mine a lot but you have to really want / need a diesel inboard to justify it.

Apolloduck has a few for sale at the moment. If you do the advanced search and select inflatables and diesel, it filters the results quite well.

[Pikey Dave]

Originally Posted by mikehhogg

...I was on a rib recently that had two 150hp petrols hanging off the transom,fuel consumption about 70 ltrs an hour. 70 lts diesel on my rib would do me a week of fishing and diving.Its a no brainer unless your a no brainer

Maybe the owner is more of a sports car man than a tractor driver. ‘Appen he’s used his brains & made his money.🤷*♂️ People have different priorities.

[willk]

Originally Posted by Philip Hodson

Inboard makes RIBs look much sleeker & sexier rather than having a great big lump
hanging off the back of the transom

Originally Posted by Pikey Dave

Beauty is in the eye of the beholder [emoji6]

Yer not wrong...

[Pikey Dave]

Originally Posted by willk

Yer not wrong...

You had to go & post that[emoji849]

[Fender]

Never felt the desire to own a inboard diesel RIB, its already been covered but for me the loss of deck area, increased maintenance costs and poor performance ( not all of them ) have always put me off - crewing on a 7.5/8m scorpion a few years ago safety boating, think it was running a Yanmar inboard and would do around 40 knots, that was after comical turbo lag, I swear the tide changed while we were waiting to pop-up on the plane

Interesting a lot more manufactures are now adding outboard/s options rather than just solely inboards on their craft, times are a changing

[jwalker]

This harping on about loss of deck space and high maintenance costs puzzles me. I have to say, mostly by folks who haven't actually owned a diesel rib. Since I have one of each I consider myself in a position to properly comment.... With a bit of forethought in the design of the engine compartment there is no loss of useful space, indeed, a flat engine cover is far more use than the dirty, sandy, salty and oilydrips rear deck of an open outboart rib. No hydraulic steering pipes, no control cables, no fuel tanks, no auxiliary engines, no oil tanks and no grubby engine well. I'm sure there is a few other nos also on some rigs.

With regard to servicing, it's just like a car, engine oil and filter, air filter occasionally and fuel filter occasionally. Outdrive oil change just like the outboard lower unit.

Issues will arise if the boat is kept in the water permanently but that is the case with outboards too.

With regard to handling, inboard engines are low mounted whereas outboards are high mounted consequently the CG of an inboard boat is considerably lower that an equivalent outboard boat. Noticeably better handling in rough water.

Fuel availability in some areas of the country is a issue for petrol driven craft so will be a major consideration. Everything is doable of course but lugging Jerry cans wears thin very quickly.

However, with regard to the op's questions, a 6.5mtr rib is a bit small for a diesel boat imho. There are limited suitable diesel engines and all are rather heavy for a 6.5mtr craft so performance will be limited. A beamy 7mtr would be better but a bigger boat would be better still.