Hi everyone.
I’m a new member here today. I am in the process of buying an Explorer 21 cabin cruiser here in England, the boat needs much restoration and has no engine (but does have a Volvo 270 stern drive)
Can anyone suggest what is the biggest engine this boat can safely accept?
Many thanks in anticipation.
Barry

Welcome!

Do you mean 21 Explorer or 21 Explorer II ?
I would guess 1965 and newer as it has the 270 drive unit.

Hello Stefan and thankyou. Yes, it an Explorer II.

Hi Barry!

As you might know the Explorer II has the same hull as 21 DC and Playmate and in fact some other models and even models made by Nimbus.

The hull can take a small block V8 and handle well.
What I have been read some people thinks it will sit somewhat rear heavy with a V8 and like a V6 better for that reason.
It will handle the power no problem.

I you think of a diesel engine you may not go over the weight of a small block V8 (with iron block and iron heads)
Hopefully some owners of the 21 hulls will shime in and give more info.

Thankyou Stephan. That’s very interesting.
I have been researching for possible engine types to install. I could take the low cost and original, with a straight four cylinder. Or, as you have pointed out, higher performance and higher cost V8.
In England, all engines are horribly expensive, even broken used ones.
Thankfully, there is much work to do before I make the final decision.
Best wishes
Barry

Hi I have a mercruiser V8 260 5.7Lt engine

Be aware of that 21 Explorer II is a heavy boat so it need a powerful engine. It will not work well under 170 hp. The optimal engine is a V6 VolvoPenta or Mercruiser it is the same base engine.
Forget four cylinder models, it will not work. the boat will be boring to drive and hard to plan
The sterndrive VP AQ270 works with older model of VolvoPenta V6/V8 depend on the drives gear ratio
For example V6 aq175A Aq205 or V8 AQ225
I have AQ175A in my 21 Explorer II, it works for me and my wife 2 person. If we are 4 person it takes some time to get the boat to plan.
Look at my website there is a lot of pictures. The adr is under "så gjorde jag"

Thank You Leonard and Sven.
That's useful information. I know the boat had an old Volvo B30 removed from it before it was abandoned.
I have the chance to buy a 7.4litre V8. But I've been told this would be too big, hence my question here.

Yes a 7.4 big block is to heavy and also to much power, and it will not work on your sterndrive.
Ok B30 Inline six, then the gear ratio will not be optimal for V6/V8. It can work if you find a propeller for this combo. But it will not work on a four cylinder engine
If you planed to keep the AQ270 sterndrive, otherwise forget the last lines.

Hello,
New to the forum and I am here in hopes of gaining some knowledge on my two 1959 Coronet 21/22 Explorers. Both boats came with a property I recently purchased and have been tucked away deep in the warehouse just waiting to get out on the water. I unfortunately am not the one to give these boats there second life on the water and am hoping to sell them, was looking for what a fair price is as well as an interested buyer. I unfortunately I am in the states and was also wondering if there is a large American following on here and if it is worth posting up a classified add.
Thanks in advance.

Ownership is now imminent. Thinking about engines again. I dont like the idea of carrying fuel to the boat for a petrol engine, (there is no dockside petrol in U.K.).
Thinking about the engine weight issue mention by Stefan, there aren’t many Diesel engines with the needed power that weigh anything near a small block V8.
I seem stuck, unless anyone can point me towards a solution?
Someone did recommend Ford, or Cummins 6 cylinder diesels, but these are twice the weight of a V8
Am I stuck with petrol as the only viable solution?
Cheers.
Barry

Hyundai Seasall, Steyr and Marinediesel all produce lightweight engines. Expensive though.

Someone installed a VW 5 cylinder diesel. It seems to work ok. So here’s a viable option.
https://youtu.be/2sxKiyPH1NY

There is very little information on engine choice in the Explorer registry but rather good documentation for the 21DC. Before making a choice for my DC I made a table of engine choices and speeds. There are som inconsistent values in the table, most likely caused by incorrect values entered by owners. I think that the most interesting finding is that a vast majority of boats have engines between 225 and 270 hp. As the Explorer is heavier than the 21DC I think that the recommendations above of a V6 or small block V8 would be an ideal choice.

Good Luck!