What would have to be done to swap out the powerhead on a Johnson/Evinrude 2cyl and replace it with one of the 49 or 56ci 3cyl? Is this possible?
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What would have to be done to swap out the powerhead on a Johnson/Evinrude 2cyl and replace it with one of the 49 or 56ci 3cyl? Is this possible?
Camohunter
It all depends on the year of the 2 cylinder. I take it that it is 2 cylinder 50, 55 or 60hp. You will need to change the drive shaft to suit the 4 spine crankshaft or if you have a late model 56ci that is a multi spline crank. You would also have to consider the gear ratios as the 50, 55 and 60hp's were 12:29 while the 75hp's were 15:28. There are a few changes to be made in the Gear Case such as a different thrust bearing carrier, water pump housing and inner exhaust housing. In relation to the midsection the bolt pattern at the adapter plate is different so you would be required to either source the 75hp s/s tower and also a different adaptor plate , exhaust housing, exhaust tuner and also the upper mounts bolt pattern is different. I would advise sourcing a 3 cylinder s/s complete midsection. Bill Ghor has one for sale on this site. If you are in Australia I may be able to help you out as I have a few s/s 3 cylinder midsections that I am currently rebuilding. You should also have a look at the parts listing for the 2 and 3 cylinder OMC.s
Stephen Medaris
Stephen thanks for the info. I'm in the States, Georgia. I've never seen one of the short midsections. I know they exist, but not many around here. I have a lot of the 49ci parts. I love the 49 / 56 powerheads. The tower and lower unit are a little heavy for my application. I want to build a motor for an aluminum river boat.
Justin Franks
a 49er or 56er with a 15" mid and nitro case should be around the same weight as the merc 40/60's that are typically run on the aluminum river boats, the 15" mid and nitro gear case from the three cylinder is the same weight as the two cylinder 15" mid and lower
That's good information. I'll see if I can find the 15"mid. So I should be able to build the nitro case out of a 40/60 short by changing the drive shaft and associated parts?
Yes, but it's a lot of parts to convert a two cylinder to a three cylinder case, I'd say only 50% or less of the internal parts are common between the two cases, different gear ratio. If you are going to run the 49er/56er you will want three cylinder gear ratio as it would be tough to find props with enough pitch to run the two cylinder ratio or the rpm's would be through the roof. The 2 cylinder gear ratio is 2.42 whereas the three cylinder nitro case ratio is 1.86Quote:
Originally Posted by camohunter