Mate about a 40hp diesel to 250-SP-C

I have 2 250 SP-C engines and they both died last summer-Had mechanic out 3 times-New plugs,wires checked timing,gas even rebuilt carbs. Anyway I been wanting small diesel engines on those drives for years- Contacted Volvo and they wont warranty the 40 hp diesel if I try to put it on the existing Outdrives so what are my options. Volvo suggested there smallest diesel Outdrive combo is 130hp -all I want is a small diesel-40hp range with an outdrive- Not against a new combination 40hp diesel with new outdrive but what are the options to connect to the SPs

Something does not sound right to me.

Both the 40 hp diesels and the SP-C AQ series drives are Borg Warner capable!
The final drive ratio choices (in this series) are: 1.61:1, 1.89:1 and 2.15:1!



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Question: why are you wanting so much reduction in horse power?
This will change the characteristics of your hull dramatically.



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Given fixed losses in outdrives it is likely that any boat that had twin 250s won't get on a plane with twin 40s. Frequent rule of thumb for gas to diesel conversion is 80%, i.e. replace 200 HP gas with 160 HP diesel for equivalent cruise (not top speed) performance. 40 to 50 HP diesels most often used (as singles) in displacement hull work boats and as engines in auxiliary sailboats in the 40 ft range.