In the 70's when there were not too many marine engines to choose from, it was common to convert an airplane engine to marine use. Most of the engines were front (crank) intake. Then as the hobby evolved, we started seeing specially built marine engines with rear intake (disk and drum). My question is, do they really have a power advantage?
Disk induction system, while simple, has several disadvantages. Most of the disks I have seen are not balanced well. Unbalanced rotor causes vibration. The drive pin can wear; and on more than one occassion, the rotor pin backed out. The resulting rod strike caused me an engine.
Drum induction system has its own disadvantages. Unlike a thin disk, a drum rotor requires dynamic balance. It is virtually impossible to perfectly balance a drum. From personal experience, if the drum housing is not bushed, the unblanced drum will cause accelerated wear.
The way I see it, a crank induction system is really a crank with an integral drum. The crank is supported by ball bearings so we don't have to worry about wear. There is no rotor drive pin to wear, or disk clearance to set. It is a very simple and effective induction system and it has worked very well in .21 size engines. Why don't manfacturers offer .45 and larger size engines in front induction versions? Is it because we automatically associate rear induction engines to performance?
Disk induction system, while simple, has several disadvantages. Most of the disks I have seen are not balanced well. Unbalanced rotor causes vibration. The drive pin can wear; and on more than one occassion, the rotor pin backed out. The resulting rod strike caused me an engine.
Drum induction system has its own disadvantages. Unlike a thin disk, a drum rotor requires dynamic balance. It is virtually impossible to perfectly balance a drum. From personal experience, if the drum housing is not bushed, the unblanced drum will cause accelerated wear.
The way I see it, a crank induction system is really a crank with an integral drum. The crank is supported by ball bearings so we don't have to worry about wear. There is no rotor drive pin to wear, or disk clearance to set. It is a very simple and effective induction system and it has worked very well in .21 size engines. Why don't manfacturers offer .45 and larger size engines in front induction versions? Is it because we automatically associate rear induction engines to performance?