Home › Forum › Ask A Member › 1956 Johnson 30hp, RD-18
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March 20, 2019 at 3:27 pm #171627
I had a parts RD18E that had a compression release head on it. (It did not have the comp release mechanism that comes from the rewind on it.) The RD18 cowl fit fine.
March 20, 2019 at 10:02 pm #171646Frank,
You are correct, the pinion gears are different numbers. Guess I got confused while cross-referencing my 2 parts lists. In any event, I’ve now located another possible source for an RD18 powerhead if I need one.Thanks to all who responded.
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."March 21, 2019 at 9:33 am #171661There are nearly no differences in these motors. The 35 has bigger pistons. I don’t think the hoods, leg, or anything else is different. The crank are the same in the 25-30-35’s…and early 40’s. So the driveshaft should not be an issue.
Should be an easy swap.
Greg
March 23, 2019 at 11:32 am #171830The 35s had a beefed up lower unit so the gears could take a bit more stress, but the lower unit from the 30 HP will probably be OK as long as it doesn’t get abused a lot.
DaveMarch 23, 2019 at 8:48 pm #171856Turns out the powerhead was total junk. Guy had left the motor sitting outside for like 15 years and had it laying on its side for the last 3. Crankcase and #1 cylinder full of rusty water and sand, pistons and crank rusted up solid. Unbelievable that people would do that to what had been a good motor.
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."March 24, 2019 at 10:50 am #171889Do not know where you live salt water area or freshwater but eBay always seems to have 30 HP. power heads on there pretty regular. I have a Johnson 30 that had a seized power head and although I am capable to rebuild it it was much more cost effective to just get a freshwater good used power head. I live in Ohio which is the mother load of old outboards. Our boating season is only about 6 months long and most old motors were not used too hard. Michigan, Wisconsin, Ohio, Pennsylvania are states with plentiful old outboard engines. There are other good states to get freshwater parts from also but the motors there are just not as plentiful. I bought my complete replacement power head off eBay from Kansas it was from a Javelin 30 HP. the guy just parted it out to get rid of it. Bought it for $75.00 plus shipping. It was in beautiful mechanical condition and obviously very low hours of use . I could not have been happier. All I had to do was change ”O” rings in bottom seal, new top crankshaft seal and a head gasket which really did not need to be changed . ( I removed head to inspect cylinders ). The motor when assembled ran beautifully my favorite outboard to use. My point here is that if you or anybody is redoing a 1950’s OMC 5, 51/2, 7 1/2, 10, 15, 18, 25 , 30 or 35 and the power head is totally seized and rusted it is much cheaper and sometimes better to just get a good used correct year power head for $50.00 to $100.00. My seized original power head would have needed everything pistons, rings, cylinder boring, bearings, gaskets, etc $$$$$$$ of dollars. My tips for getting a good used power head . 1 get one from a freshwater state. 2 look at the pictures of all the bolts and screws on power head if paint is not chipped off good sign nobody has screwed with it internally. 3 If bought off eBay look at the sellers other items if they are selling a power head most of the time they will have the other parts of engine for sale and you can get an idea of general condition over all. 4 read feedback of sellers past sales if they have 100% good feedback and good feed back comments your probably good. 5 ask them to please double box it with extra padding between boxes they get throw ed around in shipping. Sorry to be long winded but but I see a lot of people here with seized engines wanting to buy a ton of hard to get parts to get there engine going and even then probably not even using it 15 hours a year. You my friend I would look for a 1956 30HP. power head from a Johnson , Javelin . Evinrude or Evinrude lark. Why build a Frankenstein motor when you can have a correct year motor? Hope this helps others enjoy this hobby. Bill,
March 24, 2019 at 12:09 pm #171895I have seen 1956 RD18 powerheads advertised with very low compression readings. I have three complete motors . Checked one by manual starter and got around 121 PSI. Checked that one and the two others using the electric starter and got around 130 PSI.
Earlier year RDs normally do have lower compression readings.March 24, 2019 at 3:48 pm #171905I have a ’56 30hp Powerhead, but it is fully rebuilt and restored. New everything from rods to rings to pistons, plus every bearing, seal etc… and painted. So isn’t really a cheap option, but available as an option.
March 24, 2019 at 5:18 pm #171912I rebuilt a seized powerhead on my 72 Evinrude that had been used in saltwater all it’s life and even locked up it was in way better shape than the powerhead I have on this RD. There’s no way to even attempt rebuilding this powerhead – must be 5 pounds of muddy sand inside the crank case and the crank and rods are one rusted mass. I have a lead on one 56 rebuilt fresh water powerhead right now. Chris, what would you want for your? You can send me a PM, thanks.
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."March 25, 2019 at 1:01 pm #171954So one RD-18 powerhead I was looking at came back with compression readings of 105psi in both cylinders using the manual rope starter. Seems low to me. Thoughts?
Bob
1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings." -
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