Diesel v Petrol Glastron

[QBhoy]

And as said above, we were talking cruising boats - to be getting mid 20mph at 2200 rpm you must have a light narrow boat - can't see it being a 26' 2500kg cruiser to do that.

It’s 1400kgs dry. But this isn’t the argument. Show me a diesel that will do that, pound for pound. It won’t. Again. We are talking a boat of a certain ere here. This boat can come with an under powered kad32 which will be good on fuel no doubt. But you can also get these late models with an mpi. You wouldn’t even fit a diesel with the same power in the engine bay. That’s a fact. End of story.

 

[QBhoy]

Also is your petrol engine from that era?? You can't compare a brand new mpi with a 20 year old diesel thats ridiculous.

Also your boat does 65mph so thats where petrol do come into their own. A diesel doesn't need to produce as much power as its the torque that moves boats - so a 200hp diesel is the equivalent for cruising as a 260hp petrol, but obviously not equivalent for acceleration or top speed.

My engine is 17 years old.

 

[QBhoy]

I was talking about modern engines. Modern lightweight common rail diesels aremjst

must be a very small boat if you can do mid 20s at 2200rpm. I would have thought 3000 plus for a petrol engine. My 30 footer does about 12knots at 2200rpm and it will be producing a shed load more torque at those revs than a petrol v8

 

[ontheplane]

I don't get your argument?

The diesel is more efficient - full stop end of! There is no debate about that.

Can you fit a more powerful petrol engine into the boat than the diesels that were fitted? Yes of course

Would you want to? No

Are the newer MPI / GXi engines more efficient than carbs - yes

Are they as efficient as a diesel - No

You are saying that a 5.0MPi engine is a better fit for a 1495kg (i assume day type) boat for watersportsn- yes I think you are right

Is it a better fit for a 2500kg 28' cruiser - No


Is it as efficient as a diesel no, and never will be which was your initial argument

 

[QBhoy]

I don't get your argument?

The diesel is more efficient - full stop end of! There is no debate about that.

Can you fit a more powerful petrol engine into the boat than the diesels that were fitted? Yes of course

Would you want to? No

Are the newer MPI / GXi engines more efficient than carbs - yes

Are they as efficient as a diesel - No

You are saying that a 5.0MPi engine is a better fit for a 1495kg (i assume day type) boat for watersportsn- yes I think you are right

Is it a better fit for a 2500kg 28' cruiser - No


Is it as efficient as a diesel no, and never will be which was your initial argument

Are you still comparing a 170hp diesel to a 270hp petrol ? If you are...we aren’t getting anywhere.
Even at that...a Kad32 in the 28ft boat is going to be screaming at full throttle to keep on plane. The 270hp gxi in the other 26ft boat won’t be breaking sweat at canter at the same speed. Are you actually telling me this kad32 170hp is better suited to either of these boats than a 270hp gxi ? Get a hold of yourself man. The 170hp will be a nightmare in either of these. I’ll also add that I highly suspect that the Kad32 should never have been put in that larger boat in the first place. Maybe it wasn’t. A 4 cylinder screaming diesel with the canvas up in U.K. weather...full throttle at early 20’s at best...that’s if you don’t have things like a family and gear with you...no thank you !!

 

[QBhoy]

I don't get your argument?

The diesel is more efficient - full stop end of! There is no debate about that.

Can you fit a more powerful petrol engine into the boat than the diesels that were fitted? Yes of course

Would you want to? No

Are the newer MPI / GXi engines more efficient than carbs - yes

Are they as efficient as a diesel - No

You are saying that a 5.0MPi engine is a better fit for a 1495kg (i assume day type) boat for watersportsn- yes I think you are right

Is it a better fit for a 2500kg 28' cruiser - No


Is it as efficient as a diesel no, and never will be which was your initial argument

You must be getting your engines mixed up sir. Please have a look at these things before commenting with smart arse comments, you clearly know nothing about. Stick to the arm chair fella.

 

[QBhoy]

I don't get your argument?

The diesel is more efficient - full stop end of! There is no debate about that.

Can you fit a more powerful petrol engine into the boat than the diesels that were fitted? Yes of course

Would you want to? No

Are the newer MPI / GXi engines more efficient than carbs - yes

Are they as efficient as a diesel - No

You are saying that a 5.0MPi engine is a better fit for a 1495kg (i assume day type) boat for watersportsn- yes I think you are right

Is it a better fit for a 2500kg 28' cruiser - No


Is it as efficient as a diesel no, and never will be which was your initial argument

Apologies...no need for me to be as sharp with you. Not worth arguing about really. To the original question...I truly believe the gxi is a better suited engine than the under powered kad32 in either of these boats. The short block GM in some form of another has been powering boats like these effortlessly for about 40 years or more. The kad32...just won’t. It won’t be a pleasant experience either. It literally will be screaming flat out to make any form of headway at all. That’s a fact. Got to think about the harm it may do and resulting costs associated with.

 

[ontheplane]

That's ok!

We'll agree to disagree.

You are talking about a 1400 kg runabout - and for that, yes you want petrol - I wouldn't want a KAD32 in a ski boat.

In a 25' cruiser you want a diesel that's all I am saying. The KAD won't be "screaming" it will be doing 2500-3000 rpm at cruise - it's optimum speed and doing about 22mph - hardly "struggling to make any headway at all" - it will be burning a sensible amount of fuel - fuel which you can refill at your destination.

And yes the short block v8'S have been powering boats for years - in small boats. They do put them (often 2 of em) in big boats in the US because they don't give a monkeys t*ss about fuel burn as it's so cheap (but even that's changing now).

If the petrol was the right choice for a 25' cruiser, it would fetch more money 2nd hand than a diesel - a bit like a Fiesta diesel is now worth less than a petrol because no-one wants them whereas even just 5 years ago they fetched a premium..... However the fact a diesel cruiser fetches a premium is because of the higher efficiency of the diesel, the better suitability for a cruiser, the increased range and the availability of fuel.

You simply cannot compare the use of a large petrol in a light boat with a diesel in a heavy boat - it's a totally different use. It's why you don't see petrol HGV's - and very few diesel Ferrari's - they are for totally different purposes.

However to come back to the base point - the diesel is more efficient if by efficient you mean the most power out of the least fuel.

 

[ontheplane]

You must be getting your engines mixed up sir. Please have a look at these things before commenting with smart arse comments, you clearly know nothing about. Stick to the arm chair fella.

I have been boating since I was 3 months old.... first in parents boats, then my own.

I have run inflatables, Outboards (5hp through to 175HP)

in 2000 I ran a boat import business from the US, During that time I imported in the SAME version and Hull of one boat a 4.3GL (carb), 5.0GL (carb), 4.3Gi and a 4.3GXI and a 5.0 Gi - all on duoprops AND a KAD32 on duoprop - so I have direct comparisons - have you run all those engines in the same hull to have a direct comparison??

The 4.3GXi in a 1800kg boat ran beautifully - it performed well and was very efficient - and would have been my choice in that kind of trailable day boat - but it still used 1.4-2 x the amount of fuel the KAD32 did.

Perhaps I do know just a little?

 

[QBhoy]

That's ok!

We'll agree to disagree.

You are talking about a 1400 kg runabout - and for that, yes you want petrol - I wouldn't want a KAD32 in a ski boat.

In a 25' cruiser you want a diesel that's all I am saying. The KAD won't be "screaming" it will be doing 2500-3000 rpm at cruise - it's optimum speed and doing about 22mph - hardly "struggling to make any headway at all" - it will be burning a sensible amount of fuel - fuel which you can refill at your destination.

And yes the short block v8'S have been powering boats for years - in small boats. They do put them (often 2 of em) in big boats in the US because they don't give a monkeys t*ss about fuel burn as it's so cheap (but even that's changing now).

If the petrol was the right choice for a 25' cruiser, it would fetch more money 2nd hand than a diesel - a bit like a Fiesta diesel is now worth less than a petrol because no-one wants them whereas even just 5 years ago they fetched a premium..... However the fact a diesel cruiser fetches a premium is because of the higher efficiency of the diesel, the better suitability for a cruiser, the increased range and the availability of fuel.

You simply cannot compare the use of a large petrol in a light boat with a diesel in a heavy boat - it's a totally different use. It's why you don't see petrol HGV's - and very few diesel Ferrari's - they are for totally different purposes.

However to come back to the base point - the diesel is more efficient if by efficient you mean the most power out of the least fuel.

Most boats like this and about every other American boat over here that size will have a v6 or v8 GM. The kad32 isn’t up to the job on either of those boats. The 259 at a push...but the 27/28ft boat is not going to be too clever. I doubt it’s even original in a boat that size. I’ve no doubt about it. It’s under powered for a boat like that. Trust me. It will be almost or at full throttle to keep it on plane. That’s never an ideal situation.

 

[QBhoy]

I have been boating since I was 3 months old.... first in parents boats, then my own.

I have run inflatables, Outboards (5hp through to 175HP)

in 200 0 I ran a boat import business from the US, During that time I imported in the SAME version and Hull of one boat a 4.3GL (carb), 5.0GL (carb), 4.3Gi and a 4.3GXI and a 5.0 Gi - all on duoprops AND a KAD32 of the same year - so I have direct comparisons - have you run all those engines in the same hull to have a direct comparison??

Perhaps I do know just a little?

There was no 4.3 mpi or gxi in 2000. 2003ish for the mpi and I’m sure 2001/2002 for the very early gxi. I think they perhaps had one at a boat show in 2000. But that’s is. The early gxi and mpi were quite different things from 99-2000ish. But they were usually 350 or 454 things. Hope that helps

 

[ontheplane]

There was no gxi or mpi 4.3 in 2000 sir !

Nope - I imported that one later on - there were Gi's though

 

[Chris_d]

Apologies...no need for me to be as sharp with you. Not worth arguing about really. To the original question...I truly believe the gxi is a better suited engine than the under powered kad32 in either of these boats. The short block GM in some form of another has been powering boats like these effortlessly for about 40 years or more. The kad32...just won’t. It won’t be a pleasant experience either. It literally will be screaming flat out to make any form of headway at all. That’s a fact. Got to think about the harm it may do and resulting costs associated with.

Diesel debate aside, you are right when talking about these Glastrons a single KAD32 is not quite enough, seem to remember MBM did a test of this very boat back in the 2000's and I seem to remember it was struggling to better 22knts with a couple of crew + fuel etc... the V8 petrol will be thirstier but a much better match to the hull. The KAD engine versions were UK market only and trying to undercut the Sealine S25 at the time with a very low quality build as well.

 

[QBhoy]

I have been boating since I was 3 months old.... first in parents boats, then my own.

I have run inflatables, Outboards (5hp through to 175HP)

in 2000 I ran a boat import business from the US, During that time I imported in the SAME version and Hull of one boat a 4.3GL (carb), 5.0GL (carb), 4.3Gi and a 4.3GXI and a 5.0 Gi - all on duoprops AND a KAD32 on duoprop - so I have direct comparisons - have you run all those engines in the same hull to have a direct comparison??

The 4.3GXi in a 1800kg boat ran beautifully - it performed well and was very efficient - and would have been my choice in that kind of trailable day boat - but it still used 1.4-2 x the amount of fuel the KAD32 did.

Perhaps I do know just a little?

Good to hear of others with it in their blood. I could bore you to tears with my engine and boat collection. I even have 2 engines identical to each other...just because I’m a Yamaha 2 stroke nut. Been in my blood for generations. Brought up on boats since 6 weeks old on a Shetland 498. Many boats later through childhood..went to sea as a professional marine engineer for 10 years...of course leave was filled with being on boats too. Currently have boats from small ribs, 40 year old classic CVX16, Campion Chase performance, Fletcher 19 GTO right up to the 40ft princess Flybridge with her lovely Tamd61a’s. I’m a fan of all things marine...petrol, diesel or sail. But just trying to get a point across about the MPI and GXI common miss conception. They should never be compared to the older carbs...as far too many do. The reality is that very few have had the pleasure of them.

 

[QBhoy]

Diesel debate aside, you are right when talking about these Glastrons a single KAD32 is not quite enough, seem to remember MBM did a test of this very boat back in the 2000's and I seem to remember it was struggling to better 22knts with a couple of crew + fuel etc... the V8 petrol will be thirstier but a much better match to the hull. The KAD engine versions were UK market only and trying to undercut the Sealine S25 at the time with a very low quality build as well.

Totally agree. No doubt these wee kad32 pack a punch...but not enough in some boats. The s23 and s25 is a great wee thing. Wish they did one with an mpi or gxi. Exclusively kad32 though. Even a larger Kad might have been nice.
there is a 249 with a kad32 here local to me. It does ok...but runs out of puff. If the hood it up and the boat is on plane...it’s almost full throttle and you can forget any kind of conversation with the crew altogether. Very officiant going slow...but glastrons like this aren’t good at going slow. Too light at the bow and heavy at the stern with a diesel...or any engine really. Alway with a mind to lift the bow. No doubt the petrol of any kind is a better option for these.

 

[ontheplane]

Totally agree - the 4.3 GXi came out around late 2001 early 2002 from memory, I ordered the very first one to hit the UK - I just could not believe the difference - it had the ooomph of the 5.0 V8 carb with the fuel burn of the normal 4.3 carb - it was a lovely engine - and ideal for the 18-22' sportsboat unless you wanted silly performance.

I can imagine the 5.0GXi to be similar....

 

[QBhoy]

Totally agree - the 4.3 GXi came out around late 2001 early 2002 from memory, I ordered the very first one to hit the UK - I just could not believe the difference - it had the ooomph of the 5.0 V8 carb with the fuel burn of the normal 4.3 carb - it was a lovely engine - and ideal for the 18-22' sportsboat unless you wanted silly performance.

I can imagine the 5.0GXi to be similar....

Spot on. Agree entirely. You’re dead right with the comparison. The gxi and mpi pretty much all matched the power from the previous era engine above it, in displacement

 

[ontheplane]

I had heard the S23 with a KAD32 was a nice set up - 170HP in a boat just over 2000kgs should be ok?

I did also think that KAD32 in a 26' cruiser might be a bit underpowered - however my experience in 26' cruisers is that a petrol just burns far too much fuel really.

It would have been better with the KAD 42 but I don't think that was ever an option?

 

[Chris_d]

Totally agree. No doubt these wee kad32 pack a punch...but not enough in some boats. The s23 and s25 is a great wee thing. Wish they did one with an mpi or gxi. Exclusively kad32 though. Even a larger Kad might have been nice.
there is a 249 with a kad32 here local to me. It does ok...but runs out of puff. If the hood it up and the boat is on plane...it’s almost full throttle and you can forget any kind of conversation with the crew altogether. Very officiant going slow...but glastrons like this aren’t good at going slow. Too light at the bow and heavy at the stern with a diesel...or any engine really. Alway with a mind to lift the bow. No doubt the petrol of any kind is a better option for these.

Yes not a good boat at all, built down to a price plastic cleats an all, not a good boat by any measure. But could at least go well with a big V8.

 

[Lisandro]

There was no 4.3 mpi or gxi in 2000. 2003ish for the mpi and I’m sure 2001/2002 for the very early gxi. I think they perhaps had one at a boat, show in 2000. But that’s is. The early gxi and mpi were quite different things from 99-2000ish. But they were usually 350 or 454 things. Hope that helps

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