a few RDE questions

[johnyrude200]

I have a customer who brought in a 1956 30hp Johnson that he ran the wrong plugs, and partially melted the top piston. The motor wouldn’t idle well which is what sparked him bringing it to me.

He had a donor motor of the same year fortunately, so this sparked some questions I had as I was looking through the old parts books while I was transplanting powerheads. I’ve picked up some bits and pieces of these discussions over the past few years but admittedly don’t know every in and out of the changes these motors undertook in these few short years (1955-1958).

So here are my questions….

1. Why was the baffle eliminated in 1957 that goes between the exhaust housing and powerhead?
2. What are the changes that cause the 5hp increase in power (manifold/carburetor?)
3. I am assuming the carburetors are not swappable in these HP changed motors, particularly with different part numbers?
4. Is there a reason why the airbox and starter brackets changed. The donor motor had an original starter bracket with clearly an original starter from 1956; the customers daily driver motor had a new starter with an all metallic bracket.

On both motors, when I pulled the powerheads, the exhaust relief cover/baffle (PN 304875) were completely separated from the exhaust housing with no screws holding them down. Just a coincidence?

Have to say these motors seem pretty easy to work on and simple, easier to pull a powerhead on one of these RD motors than FD line. I’ve only worked on a handful of the RD models, but probably a couple hundred FDs.

Thanks for taking the time read this post and revisit the topic. I know it’s been discussed a lot of times already!

I haven’t been posting much the last few months because I’ve been busy renovating the property my wife and I acquired in fall of 2016, and just in the daily grind/life responsibilities. I work full time on pre 2007 OMC motors for a living and what I’ve been finding is that working on anything carbureted has become a niche. New techs know very little about them and marinas selling today’s motors generally can’t work on them because they have no staff to competently provide service.

Just wanted to thank fellow members of the AOMCI for your time and willingness to share knowledge. I wish there was a way for me to go to the old J/E school for the rubber stamp, but they aren’t available. The AOMCI is the next best thing!

[olcah]

Your 1st question is a hard to answer. There are a couple of conflicting opinions whether to use that baffle or not. Here is what I could find out. viewtopic.php?f=2&t=10757 I used a 1956 Johnson 30HP last summer w/o the baffle and it ran well.

[Author]

Posts