Volvo MD4 Merc 636 power differences

[Ifraser]

Hi, I have a Storebro Royal Cruiser with twin Volvo Penta MD4's rated at 30 hp each. I have discovered that they are the same engines as Mercedes OM636 rated at around 42hp. Does anyone know where the difference lies and can the Volvo's be uprated simply. That extra 24 hp could be really useful! Thanks Iain


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[seaspray]

hello perhaps you can help me my friend has a 1976 merc om636 36 hp and it has a wet exhaust thro water lock and the outlet is very close to the water line is this ok or should it be alot higher because when sailing on one tack it is under the water
regards robin