Sea Ray Sundancer Boat Engine Swap

[Iolare]

A friend of mine has a 22' Sundancer with a Mercruiser V8 that he wants to sell and I'm considering buying. The engine and manifold (raisers?) need rebuilding and/or replacement, so what about swaping it entirely with a diese engine? I've had great performance from my Mitsubishi Triton diesel and wonder if such an engine could be fitted into the boat, and mated to the outdrive. I'd like the economy and reliability of a Japanese diesel engine if it's feasible.

Does anyone have any experience with such a swap? Can anyone recommend a shop in the Phuket area for this work? Is this even a good and practical idea? Your comments and suggestions would be appreciaated.

[garyh]

It is quite feasible some points that will need to be addressed include heat exchanger ( raw seawater will eat the engine away in not time) and propeller matching to the engine. Diesel is a safer option than petrol also as it does not have a vapour explosion risk which can be very nasty,

[MikeyIdea]

Yepp, good idea. There are so many boats in Thailand that use converted Hino truck engines - bigger boats like ferries, fishing boats. Those truck engines converted for marine use work very well indeed. I have heard of smaller boats using converted pick-up diesels too but never actually seen one in use. No reason why a converted pick-up engine wouldn't work fine

I do not know of any shops who do marine conversions of pick-up engines but I bet there are several in Thailand. Many bigger long-tails are using pick-up diesels, you want a bit more sophisticated conversion than that of course but should also be possible to find. Ask around and don't give up if you don't get any numbers to the pick-up engine converter shop, maybe you'll have to call and ask the Hino truck engine converter shop and he will know

[katabeachbum]

Depends on which Mercruiser Bravo drive you have

Bravo 2 and 3 can handle Toyotas 4,2 inline 6, in Marine edition sold as Yanmar +300hp @ 3800 rpm as i recall. diesel

Most Hino are low rev engines and do not perform well in light fast boats

Mercruise has a 4,2 inline 6 diesel too, Italian VM Motori builds the engine, Mercruiser adapt cooling and exhaust for marine use.

[Iolare]

The outdrive is an Alpha 1 model, and the Mercruiser is a 5.0L V8. I suppose that means that the Toyota diesel wouldn't work with the outdrive. I could find a Bravo outdrive as the present one needs a rebuild, so maybe I'd be looking at a swap of both the engine and the outdrive.

This boat is quite the project boat, as it has sat outside on its trailer in the weeds for the last 5 years. It will need a total makeover and I want to be careful not to have more in it than it's worth when it's done. The cost considertions would probably eliminate the Mercruise diesel, so either I find a motor from a wrecked pickup truck and a willing and able mechanic, or I abandon the idea. But I'd like to do it, because I think it would be an economical cruiser to run with the diesel.

I'm still hoping there's a shop in the Phuket area that has experience with this kind of work. Thanks for your suggestions and comments so far. Here's a picture of the project:

[katabeachbum]

The outdrive is an Alpha 1 model, and the Mercruiser is a 5.0L V8. I suppose that means that the Toyota diesel wouldn't work with the outdrive. I could find a Bravo outdrive as the present one needs a rebuild, so maybe I'd be looking at a swap of both the engine and the outdrive.

This boat is quite the project boat, as it has sat outside on its trailer in the weeds for the last 5 years. It will need a total makeover and I want to be careful not to have more in it than it's worth when it's done. The cost considertions would probably eliminate the Mercruise diesel, so either I find a motor from a wrecked pickup truck and a willing and able mechanic, or I abandon the idea. But I'd like to do it, because I think it would be an economical cruiser to run with the diesel.

I'm still hoping there's a shop in the Phuket area that has experience with this kind of work. Thanks for your suggestions and comments so far. Here's a picture of the project:

I believe Alpha one is unable to cope with the tourque of a diesel. Its a light build go fast outdrive for light boats

[H2oDunc]

You might get good performance from your Triton on the road but trying to push a boat through the water is a totally different thing all together. My advise would be to find a boat that has a good engine to start off with. Yes there are plenty of diesel engined boats out there but they are slow, economical and reliable but hardly ever fast.

Before all you people start the what about this etc Yes there are some, especially ribs but the boat in question was designed for a petrol motor not diesel.

[katabeachbum]

You might get good performance from your Triton on the road but trying to push a boat through the water is a totally different thing all together. My advise would be to find a boat that has a good engine to start off with. Yes there are plenty of diesel engined boats out there but they are slow, economical and reliable but hardly ever fast.

Before all you people start the what about this etc Yes there are some, especially ribs but the boat in question was designed for a petrol motor not diesel.

say that to VW/Audi and their marine converted diesels :lol:

modern diesels are fast, a 300 hp Yanmar is actually faster than a 300hp V8 petrol, since it has higher tourque and needs to carry half the fuel to cover same distance. well, thats a decade ago.

todays commonraildiesels need even less fuel (weight), so is even faster

a Triton works fine, since the powerband is similar to commonly used small (2500-4200cc) marine diesels, 2000-4000rpm. OPs existing 5,0 is approx 200hp, but has less tourque than Triton, so expect same perfomance from 5,0 petrol 200hp and 165hp diesel, thats 25-32 knots in this boat @ 3600rpm.

sufficient cooling of exhaust and engine coolant is the tricky part, and loads of fresh air is needed to burn. and a heatshield for turbo

[garyh]

Diesels have torque down low and thats where it really counts to get a boat up on the plane quickly. This boat was Diesel powered and won lots of races.

[BSJ]

Seems like a good idea, All you need is the right diesel! Most of your Hi-Lux/Triton 4's are to underpowered....unless they have a turbo fitted. Even then they maybe iffy! A Toyota 6 as mentioned would be a good option if it can fit. And you will need a stainless steel coolant water/salt water intercooler. Let us know how it goes.

[sibeymai]

The height of the engine will also be a consideration. The marinised V8 will most likely be fairly low in height whereas a straight diesel may be taller. Could be an important consideration if the original engine fits below the cockpit floor.

You will need to ensure that the exhaust manifold risers are high enough to prevent water from entering the exhaust and reaching the cylinder heads/valves. The weight of the diesel may affect the waterline level thus affecting the needed riser height.

As for RPM, I wouldn't expect any problem with the Mercruiser petrol versus an automotive diesel.

[melvinmelvin]

Would be interesting to hear how you progress with the project, if you decided to go ahead with it.

I'd just like to add a further consideration which you may want to take into account:

An engine in a boat is often subjected to higher loads over longer time than a car engine.

That is being run at full speed for hours on end.

An ordinary car engine is not built for that. You don't normally drive ordinary cars for hours on end at full speed/load.

If you put a car engine (say 200 hp at (full speed/load) max revs) into your boat and manage to tune engine/gear/screw

so that you get 200 hp out of it I don't think the engine would last very long.

If (for example) a 200 hp marine engine installation would be a normal installation in your boat you would need

a significantly more powerfull car engine installed and you would need to adjust the whole installation so that you

take out much less than its maximum power when you run the boat at full speed.

That is, if you want the engine to have a long lifetime.

[katabeachbum]

Would be interesting to hear how you progress with the project, if you decided to go ahead with it.

I'd just like to add a further consideration which you may want to take into account:

An engine in a boat is often subjected to higher loads over longer time than a car engine.

That is being run at full speed for hours on end.

An ordinary car engine is not built for that. You don't normally drive ordinary cars for hours on end at full speed/load.

If you put a car engine (say 200 hp at (full speed/load) max revs) into your boat and manage to tune engine/gear/screw

so that you get 200 hp out of it I don't think the engine would last very long.

If (for example) a 200 hp marine engine installation would be a normal installation in your boat you would need

a significantly more powerfull car engine installed and you would need to adjust the whole installation so that you

take out much less than its maximum power when you run the boat at full speed.

That is, if you want the engine to have a long lifetime.

it is actually opposit. a car engine or industrial engine is usually tuned to perfom better than when installed in a car. The higher hp and frequent use on max revs gives boat petrol engine lifetime of approx 1.000 hours while in a car approx 6.000 hours/200k km. For a Marine diesel the figures are 3.000 hours while in a truck/bus 15-20.000 hours

[melvinmelvin]

Yes,

but I still think we're saying the same thing.

Maybe my entry was clumsily worded, but hinting at the same as you.

[katabeachbum]

Yes,

but I still think we're saying the same thing.

Maybe my entry was clumsily worded, but hinting at the same as you.

and most marine engines are used less than 200 hours a year, making them die from age and corrosion before they are worn out

[H2oDunc]

I have just had a chat with the local boat guy here on Samui and he just laughed.

Show me the boat when you have finished throwing in a Toyota diesel pick up engine into a high performance boat and I will stand corrected.

[WarpSpeed]

My goodness the trailer's in better condition then the boat, all I can say is I don't envy you, that's a bigger project then I'd be up to. Though I love boats too, sadly a boat is just a hole in the water you throw money into and this one isn't even in the water yet ..

[katabeachbum]

I have just had a chat with the local boat guy here on Samui and he just laughed.

Show me the boat when you have finished throwing in a Toyota diesel pick up engine into a high performance boat and I will stand corrected.

Toyotas diesel 4,2 inline 6 is sold by Yanmar as a 330 hp on Bravo 1-3. One of the most sold stern drive diesels in the world. Not in Thailand tho

and of course Volvos diesel 3,6 liter providing 300 hp on duoprop in my boat in 1998. +50 knots Replaced a 270 hp 350 V8 petrol sipper. Doubled range and gained 3 knots topspeed :D

afraid the local boat guys here in LOS dont know much about anything else than longtails, outboards, slow rev large inboard diesels (mostly Hino) and a few V8 petrol sterndrive

BTW a BMW 2,0 inline 4 on sterndrive now produces 220 hp@4000rpm and 450 Nm@1800 rpm. Outperforms most

[melvinmelvin]

If any of you guys know anything about boats & certificate requirements in LoS I'd be happy if you could

take a look at entry 18 and 19 in this thread;

[H2oDunc]

I'm not trying to say that diesel engines in boats are a bad thing. Far from it they are a great thing. The point I am trying to get across is a boat like the one in question has been designed to be propelled by the motor that is fitted to it. dropping in a pick up diesel as was being suggested isn't going to make it much of a boat. A dedicated marinised diesel engine is another thing in question.

My friends supercharged, turbo Volvo Penta diesel engine cdrtainly shifts his rib at a rapid speed and the economy is far better than any outboard.