1975 6HPs (Models 6504/6505) -- how does the '75 vintage compare?

[Good Trout To You Sir]

Anyone have a view on the comparative reliability, parts cost and repair ease of the 1975 6HP OMC model year vs the 6HPs before and after? Any noteworthy differences between the 6504 and 6505 variants? Assuming cylinders are relatively balanced, what compression results do I want to see? Thanks.

 

[racerone]

These were essentially the same from 61 to 79 models.------OK there are some minor differences.-----Consumable parts are easy to get for all of them.-----In fact easier / cheaper than much newer motors.-------- 6504 and 6505 are different by 5" of shaft length

 

[oldboat1]

^^+1. Easy for the DIYer to maintain.

 

[jimmbo]

1965 was the first year of the 6hp, in prior years it was a lower revving 5 1/2

In 65 or 66, the drive pin was relocated from the rear of the Prop to a location in front of the prop, also in 66 the prop was changed from Aluminium to Plastic

 

[Good Trout To You Sir]

Thanks, guys.

 

[TN-25]

1966 as was said, the drive pin was relocated. The bigger picture is that they switched from a shock absorber in the lower unit to a splined prop shaft. Just so you couldn't run an early non-spline prop on a later non shock absorber lower unit (or vise-versa) they purposely made it so props between the 1954-64 5½ & 1965 6-horse are not interchangeable with the 1966 through 1979 6-horse.

For 1977 they switched to CDI ignition. Supposedly better, but if the CDI box fails it is expensive to replace.

I think any 1966-76 6-horse is your best bet.


A little history as far as the lower units are concerned, the 1954-55 Johnson 5½ & Evinrude 7½ shared a 1st generation "Aquasonic" or "Suspension-Drive" lower unit with a detachable exhaust bypass cover. Gale also used them 1956-59 on their 5-horse.







They redid them for 1956 into a sleeker style with lower swivel bracket rubber mounts under "muffs" and were used on both the Johnson & Evinrude 5½ & 7½ (Gale used this as well on their 5 from 1960-63). This midsection & lower unit shared the guts & foot with the earlier style. The later style looked the same from 1956 through 1979 except the bump or "hook" that ran in line with the prop shaft forward was eliminated for 1968. (compare the 1967 "bump" to the 1975 "no bump" Evinrude pictures attached)

 

[Chinewalker]

The 6hp never had a splined propshaft. It was pin drive right up to the end in 1979.

 

[racerone]

I think he talks about the spline for the clutch dog.

 

[TN-25]

I certainly worded it incorrectly. I should have said "rubber-cushioned slip clutch" or "solid rubber bushing", not splined prop shaft. The point is they ditched the older shock absorber for a new approach in '66.

 

[thatone123]

For me anymore, "1975" is kind of the cut off point of outboard practical use. Before that the carbs and fuel systems are more complicated as to easy access and easy maintenance and speed as to being worked on unless you worked on them from early on. Also as you go back further you have to deal with the non-1 piece cowling which I hate and they invented the 1 piece cowling for a reason. (simple and faster) Also the major parts houses now are not carrying parts past 1975 as the outboards before that are getting scarce. The early outboards are great no doubt, but as time went on working on the newer ones became faster, less hassle and more productive time wise. I love the old portable outboards, but just not practical for how I use them which is very hard. In the portables hard to beat the 6, 9.9/15 models made in the 70's until the late 90's by OMC. In effect they were the "new" modern outboards as they advertised back then. Also a few independent type parts houses will really stick you for the cost of parts they know are scarce but are only available from them. And again, it takes more time to procure the parts as to searches and other assorted ways.

 

[racerone]

These older outboards are easy to work on !!----No special tools required for the average owner.-------And 123 how are you making out in getting the propeller off one of these modern motors ??

 

[thatone123]

That is a much more "Modern" motor that the ones I talked about. That range of vintage have a whole stack of "modern" problems to deal with like Cheap China Plastic Over Technologized Wonders.

 

[Bonaventure]

I owned a 1971 or so 6 HP Evinrude. It was a great motor, I bought it about 1979 and used it for a couple of years. Wish I had never sold it.

 

[82rude]

I have a 74 6HP JOHNSON.Outstanding ,reliable ,great running motor.Never to be sold.

 

[Steelhand]

My 79 6hp Johnson 6r79e is my first child in the small boats grand scheme of things that float. It sat a decade when the previous owner passed. Hooked it too a fresh tank of mixed, 6 pulls later, she was running like it sat only a week. I have a spare carb serviced with a rebuild kit waiting for the day it gums up. A spare kit awaits it also. I have collected many spare parts for maintenance and plan to pass it to my son when I go. I will cherish it for rest of my time. I think I'll run it this week for no other reason than I can.