Merc V6 petrol - Diesel Conversion

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enterprise

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I know that in the past there have been posts on the subject of re-powering with diesel but has anyone done a straightforward swap for what is probably the most common mercruiser, the 4.3l V6.

How straightforward is conversion?
What engine would be a direct replacement?

205HP V6 petrol - what diesel?

Is there an engine suitable as a direct bolt in replacement onto the Alpha 1 or do both require replacement.

Is it possible to install another manufacturers engine inplace of the merc, ie volvo etc.

Would like to know how successfull the repower was if you have done this conversion, might repower our Sealine s240 if feasable.
Thanks
Andy
 
I know that Mercruiser do supply there drives to other 'customer' engine packages - such as Yanmar and Nannini. The gear ratio will certainly be different for diesel compared to your V6, but I don't know if this can be fudged by leaving the ratio and playing around with the prop size/pitch.

I would have thought something like the VP D3 160hp would be a good replacement if you are looking at new - you don't need as much power in a diesel as you do in a petrol as the torque is much higher and is more useful in the marine environment.
I know S23's go well with the KAD 32 which has 170hp.

Another option would the the Mercruiser 1.7 D-Tronic. I think this engine is still available, and comes in 150hp format. This may be one to look for on the used market as well. This is also the most likely to enable you to retain your drive.
 
Had wondered about the 1.7 D-Tronic, being single engined would the 1.7 provide enough power?

Torque would be higher but would it counteract the loss of 50+ Hp, would I need to opperate at full power to maintain planning speed or have I got this torque-horsepower thing totally wrong?
 
I have seen the 1.7 in 23/24 footers, but I have never used one. I have been out in the Bayliner 285 with a 240hp Yanmar, which went just as well as my Merc 300hp petrol.

Thing is, with your engine bay, I suspect you are really looking at a 4 cylinder unit. Did you click the link I posted in my second reply? Looks like a good options, and has the same power as the V6 so .... Whooooooosh! /forums/images/graemlins/grin.gif
 
the 1.7 would be way underpowered and only swings one prop, careful on the d3 160, the kad32 has nearer 190hp which is why d3-190 was launched. but changing from merc to volvo is more complicated as different shape thru transom
try yanmar route, they have a good reputation.
 
He only swings one prop at the moment (alpha 1). I agree that the 1.7 might be a bit underwhelmed, which is why I suggested the 3.6 - 4 pot and with 200hp would be perfect as it would match the drive.

I don't think I have ever seen a KAD 32 with 190, they were rated by VP at 170, and most older ones will have dropped off from that.
 
Thanks Jez,

Good call with the 2.8, will Google for specs & Info, right about 4 pot, access & weight probably limiting factors, S24 was built with Volvo diesel option so know boat is capable of installation.

Yanmar as sudgested by Carl could be another option but I still would like to here from anyone who has swaped a 4.3 for a diesel.

Guess I need the positive push in the right direction to proceed further, cost maybe the crunch but thought that as the 4.3l was so common maybe a manufacturer had designed a bolt in replacement by now.
 
1.7 will be very underpowered compared with your current. My boat has the 4.3, and another identical boat supplied new with the 1.7 was sluggish in acceleration, and no where near the top speed I have.
 
My Sprint had a 205 V6 in it. I ended up with the Yamaha 370 sti. A great engine and the Hydro drive leg knocks spots of anything else. Mods required to engine beds but nothing major and transom needed laminating and then cutting.
 
Just to add to the higher torque and less HP comments.

I swapped out a 230hp V8 for a 170hp KAD32, going from single prop to duo prop and I acheived 30 knots. From new with the V8, the builders quoted a top speed of..........30 knots! So it would seem that my 60hp reduction has made no difference to top speed. Acceleration may be a bit down, I can't really tell but overall a good swap.

KAD32's are no longer available new although if you hunted around you may still be able to find one in stock somewhere and possibly at a very good price as an out of production engine. It would also make sense to put this combo in as it was an original option on your boat making it perhaps more sellable.
 
I understand the Yanmar is impressive - and I believe it can mate to the Alpha leg (although a Bravo 3 is normal- someone will confirm that) they do a few outputs in the 4-cyl incl 240HP so that's worth thinking about.

I hear the Yamaha is amazing too - can't think why more aren't in boats...
 
Speak to Mike Wills in Poole, hes done plenty and knows his eggs.
The kad32 is supposed to be 170, but 2 volvo peeps have told me d3-160 was tried in s23 and couldnt pull like the kad32, hence volvo had to go back and find more hp, then then retested kad32 and found it closer to 190 and not 170. Could be load of garbage but seems odd that i've heard that twice now.
 
definitely need to change gearing in legs (not entire leg though) if you stick with Alphas.

was looking at a similar project 2x300hp petrols for 320hp diesels....if you don't change leg gearing top speed is half what you would hope for!!!!!

petrol revs to 4500 or maybe 5000....diesel rpm will be lower so it gets made up in the leg
 
I watch the posts with interest with people trying to help but giving the incorrect info.
Hope i can help.
We have many S24 / 240 senators we look after lots with the 4.3.
The 1.7 is not a d tronic engine i.e is not electronically controlled...no ecm etc.
The 1.7 will only run on the 2.00:1 ratio alpha drive. It is the only Alpha that will take the torque. With the correct propping you should see 30knots but thats pushing it.
The 2.8 is an option comes in 170 or 200 hp it will fit in the 24 engine bay with a few mods but would be a tight install....thinking of servicing this would also cost for the engine around £15k
The yanmar 240 wont fit + be too heavy
The D3 160 or 190 would fit fine and the transom cutout for that engine is for the SX drive which will not require much moddong to the existing cut out.
The cheapest option is the 1.7 otherwise i would go for a D3 160 which you can have on duo prop

hope this helps
 
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