Perkins or Nanni

[jecuk]

Hi everyone, I am looking at a boat with twin Perkins 4-108s. Many similar classics seem to have been updated to Nanni 2.5ltr. Is there a significant performance difference or are the Nanni just the latest thing which you can put in if the Perkins die?

 

[miket]

In my view there is nothing wrong with the Perkins 4-108 other than it is getting a bit long in the tooth. It will be noisier, rougher and less economical than the modern Nanni engines, but for £10k + cost of replacing 2 old engines you need to be sure that you will derive that sort of additional benefit post replacement.

 

[jecuk]

Thanks.

 

[sailorman]

i re-engined 5 1/2 yrs ago the perky 4108- 1700cc ran @ 2700 RPM with my Max prop
the new Nanni 37.5 Hp - 1500 cc needed the prop pitch changed ( courser ) to achieve 2800 RPM ( the Nanni rated @ 3000 RPM ).
if you get more Hp from the 4108 I.e. rated up to 48 Hp the 43 Hp Nanni would be more appropriate

 

[jecuk]

Now the boat will do about 9-10knots with the twin 4-108s. Would the Nanni's change performance meaningfully or is this the likely right top speed through the water for my boat?

 

[sailorman]

wot is the RPM @ that spd

 

[jecuk]

I think about 2800 but need to do some more checking.