Relcraft mercruiser 140hp to diesel engine

[jimmyht]

Hello all, I'm looking for some advice. I have a 1980 24' Relcraft with a Mercruiser 140 hp/pre alpha "r" type leg. Its a lovely boat but too heavy on the petrol.
What I would like some advice on, is there anyone out there who has changed their engine to diesel. If they have, can they tell me.
A) is there an engine that easily fits.
B) the cost
I'm retired now so time doesn't matter. The boat club I'm in, is full of helpful members.
The problems I can see are:
1) keeping the fwd/rev linkage for the leg, but having a seperate throttle lever for the new engine.
2)Engine cooling will be different, so might have to drill holes in hull.
3)I'm not sure about revs/thrust/prop size, I know that the hull of the boat was made to plane, but I would be happy if I could get a healthy 10+ knots out of her leanly.
Thanks everyone................jim

 

[Chris_d]

Try Lancing marine they offer lots of straight swap diesel conversions, however your not going to get a 24' planing cruiser to be economical at 10 knots regardless of engine type, its will be frugal up to its displacement speed of 6-7knots and once up on the plane at 16-17knots but in between it will just be using power to push water and very uneconomical, are you sure this isn't the problem as a 140hp merc doesn't use a lot of fuel?

 

[volvopaul]

Firstly an alpha leg won't take the torque from a diesel so your wasting your time trying to marry the equivalent hp diesel to it, also the gear ratio will be wrong, the alpha type leg is just like the bottom of an outboard with a dog gear for in or out of gear it won't last long.

Unless your say looking to marry it with a 50hp diesel, but the speed will be low unless you alter the prop which increases the torque on the drive, vicious circle in my opinion, better to look around for a complete package from another boat, I e leg shield, engine loom and dash etc, there are some around for sure look on boats and outboards and eBay.

 

[scottie]

Try running the boat at non planing speed and and then look at fuel costs because if you are happy to accept low hp diesel performance it might not be that different using existing petrol setup and won't cost anything in the short term.

 

[Spi D]

Before parting with money do some budgets for various scenarios.

Maybe selling her and getting one better suited would be the right solution, at least if
you look at the total cost over the next years.

 

[Elessar]

Hello all, I'm looking for some advice. I have a 1980 24' Relcraft with a Mercruiser 140 hp/pre alpha "r" type leg. Its a lovely boat but too heavy on the petrol.
What I would like some advice on, is there anyone out there who has changed their engine to diesel. If they have, can they tell me.
A) is there an engine that easily fits.
B) the cost
I'm retired now so time doesn't matter. The boat club I'm in, is full of helpful members.
The problems I can see are:
1) keeping the fwd/rev linkage for the leg, but having a seperate throttle lever for the new engine.
2)Engine cooling will be different, so might have to drill holes in hull.
3)I'm not sure about revs/thrust/prop size, I know that the hull of the boat was made to plane, but I would be happy if I could get a healthy 10+ knots out of her leanly.
Thanks everyone................jim

done it twice.

you have to enjoy the process.The time and cost for little bits you overlooked escalates.

the only one that stands a chance of fitting without major mods is the 1.7 engine which IS on an alpha leg.

Don't even think about keeping the leg you've got.

 

[rafiki_]

done it twice.

you have to enjoy the process.The time and cost for little bits you overlooked escalates.

the only one that stands a chance of fitting without major mods is the 1.7 engine which IS on an alpha leg.

Don't even think about keeping the leg you've got.

As Elessar says, there is a 120 hp Merc diesel 1,7 litre Isuzu engine. Same base engine as the Astra Van from 10 years ago. Very economical, and married to a CMD Alfa bravo leg. I have 2 of these on Rafiki, and very happy to date.

 

[jimmyht]

Thanks for the input

Thanks for the reply,s. I will have to do some testing i.e. at 6 knots then on the plane, to see how she drinks fuel. Ive kept her off the plane (thinking its cheaper) that might be wrong.
thanks jim

 

[Warpa]

You dont say how mych fuel you are buring at the moment, i have a 135 hp mercruiser and at 6 knotts i think i would lose interest long before it used a tank of fuel, it would take days. Pushing at 10 knotts just before its trying to break onto a plane would be the same as a snow plough effect.

Plus any saving on fuel you make by doing the conversion would take years to pay itseflf back.

 

[boatmaster]

Hello all, I'm looking for some advice. I have a 1980 24' Relcraft with a Mercruiser 140 hp/pre alpha "r" type leg. Its a lovely boat but too heavy on the petrol.
What I would like some advice on, is there anyone out there who has changed their engine to diesel. If they have, can they tell me.
A) is there an engine that easily fits.
B) the cost
I'm retired now so time doesn't matter. The boat club I'm in, is full of helpful members.
The problems I can see are:
1) keeping the fwd/rev linkage for the leg, but having a seperate throttle lever for the new engine.
2)Engine cooling will be different, so might have to drill holes in hull.
3)I'm not sure about revs/thrust/prop size, I know that the hull of the boat was made to plane, but I would be happy if I could get a healthy 10+ knots out of her leanly.
Thanks everyone................jim

I know of a Relcraft (an Emerald i think) that had a Steyr diesel fitted in place of an OMC petrol. as far as i am aware all went well and the boat maintained some performance. i saw the boat some time back for sale on the Medway. called 'Marlin B'.