1958 Johnson Fat-Fifty Acceleration?

[PhilfromOhio]

Does anybody know about the "linkage" that extends from the magneto to the carburetor? I'll give you a quick history of repairs and what it is doing to better address the question. I have replaced the plugs, wires, points, condensor, new timing belt, properly timed to all marks as indicated on engine and manual. Bebuilt the carburetor, new o-rings on needles, new gaskets, completely soaked the carburetor for 3 days in a tank of thinner, air compressed it out and checked allports, all clear, New float, new needle and seat in as well. It fires right up every time and gets up on plane, but slowly. The fuel pump has been completely rebuilt as well, new diafram, springs ect..
My question is should I attempt to adjust the linkage that extends from the magneto to carb when she is under full throttle? I cant believe how quiet this engine is? Is that normal? Once I open the access door to the carbs its really loud though? Normal operation noise. I can tell the motor is just struggling a bit and I am at about what I would guess 80% power. The linkage adjustment is the only thing I havent tried, but wonering if that would be a waste of time? Could be something else?

 

[Daviet]

Re: 1958 Johnson Fat-Fifty Acceleration?

Is the boat new to you, has it ever jumped up on plane quickly?
What RPM is it running at when running at WOT?
It almost sounds like a prop or weight problem, what size boat is it?

 

[PhilfromOhio]

Re: 1958 Johnson Fat-Fifty Acceleration?

Yes the boat is new tome, I had to completely restore it. New transom, floor, rub-rail,carpet ect... It is a 15' 1964 Sears Deluxe. The engine was last ran in 1984. It had been stored open in a barn. When I got it I was told the motor didnt work. Well, I dropped some fuel and pulled it...surprise it fired first pull. However the dead lady-bugs and mouse nests came out of every possible hole. I had to completely rebuild the lower unit, and everythinng else, minus putting new head gaskets on. I put 3/4" marine plywood floor in, instead of fiberglass. The floor was in excellent shape, but I still replaced it with plywood, and then woven-roving material and resin over the plywood. Could the boat be a bit heavier now? It is real slow to come up on plane, but it does get there. I have seen videos of this motor running and mine doenst seem to rev as high. I am unable to tell the rpm's? minus installing a guage somewhere how could I tell what they are? Is there a porta-guage or something out there?

 

[TN-25]

Re: 1958 Johnson Fat-Fifty Acceleration?

That motor should be able to push a boat of that size to about 28 mph. There was only one prop offered on the 1958 version. For 1959 the prop was changed to more pitch and a smaller diameter. At that point the 1959 prop was the only one offered from that point on through OMC accessories. Still figure on the same speed.

How's the compression? Have you verified that it is hitting on all four cylinders?

 

[PhilfromOhio]

Re: 1958 Johnson Fat-Fifty Acceleration?

I am going to assume it is hitting all four cylinders. I have absolutely fantastic spark on all four. When I checked the plugs they all seemed
equally used, none oily or fouled. I did have to put a helicoil in the lower port side plug hole, but it is holding fine. No oil residue around threads like I have seen on some helicoils before. So, there is only one prop for that motor? Could I use one from 1959? I wouldnt think the shafts are a different diameter? I am still curious about the linkage from the magneto to carb adjustment? any thoughts on that?

 

[TN-25]

Re: 1958 Johnson Fat-Fifty Acceleration?

I have never run through a link n sync procedure myself, but since you have taken care of many other possibilities it may be a logical step. Again, did you perform a compression test to see aprox. where your cylinder pressure is, and also to verify that your cylinders are reasonably even? A dead or loafing cylinder will definitely make a motor lazy under load.

As for the props, yes they are interchangable between the '58 & '59. Gear ratios are the same at .586 (17:29). The '58 prop was 13" x 13"; '59 was 12 1/8" x 14". Lower units were revised for 1960 on the 75 horse; Gale also combined the revised 1960 lower unit with the old 70.7 c.i. powerhead of the 50 horse but rated it at 60 horses (expansion chamber tuning or intake tuning?). Of course Johnson & Evinrude adopted the Gale 60 V4 when Gale was winding down operations for 1964, keeping the 60 horse V4 in production through 1967, then boosting it to 65 horses for the final 70.7 c.i. V4 in 1968 (new Power / Pulse solid state ignition & surface gap plugs were added from the 1967 100).

Just a thought, but have you actually weighed your boat after the rebuild? What about hull fouling (I doubt you wouldn't have addressed it were it a problem), or perhaps cupping of the hull if it sat on a roller bunk trailer for a long time? Is your motor set too low into the water? Another thought: is your propeller been verified as true to spec?

 

[steelespike]

Re: 1958 Johnson Fat-Fifty Acceleration?

The 50 is rated at 4,000 rpm.Really old school.A tinytach costs about $40,easy to install could be used temporarily. It will work on any 4 cyl.2 stroke. Be sure to read all info it is kind of an oddball setup.Also would be very good to get the speed gps is best.
Have you carefully adjusted the highspeed jets?The high speed nozzle requires a special tool to install.Manual says not to remove or renew unless the tool is available.
Is the choke opening all the way?If I was searching for a little more umph I would carefully advance the distributor.You may be able to simply advance it a little by hand with out messing with the linkage untill it seems indicated.You might also observe the linkage for wear.

 

[Chris1956]

Re: 1958 Johnson Fat-Fifty Acceleration?

That fatty should plane a 15 footer in a few seconds. They specialized in low end power.

OK, lets run thru the link and synch procedure (from my failing memory). Turn flywheel until timing mark aligns with mark on block and pull starter. Advance throttle until timing mark on pully base aligns with mark on black magneto bracket. At this point, brass carb cam should just touch carb throttle roller. Adjust link between magneto and carb to make is so. Remove point wire from stud on distributor. Put a test light or ohmmeter on point wire. Remove timing belt. Turn distributor puller and observe when points open on meter/test lamp. Points should open just as pully hits timing mark. Now turn pully to next timing mark (90* further on, and hard to see). Adjust second set of points.

Re set timing belt, so timing mark on pully aligns with pully base. That motor will never rev up very much, but you should get 28 MPH with a decent 14" pitch prop.

BTW - all cylinders should have 90+PSI compression. Sometimes the bottom cylinders need a few seconds to begin to fire after a cold start, for some reason. You shoul never foul a plug, if everything is adjusted properly. Did you set the carbs High speed jets and low speed jets?

 

[PhilfromOhio]

Re: 1958 Johnson Fat-Fifty Acceleration?

Gents, thankyou all for the information. I will certainly run the compression test again. I ran it earlier this season with a really old guage, that has the rubber cone and had a buddy pull it and the readings were in British measurements as I restore classic Brit cars for a hobby. Anyway, it was not the best test, I have recently purchased a screw-in tester and will try again. Question is, do I use the pull start to test or can I use the starter? And should I test after she is warm? Second, it has been on a trailer for along time, but not a roller type, 2X6 carpeted rails and the hull is completely supported, however when it is on plane it does spray in the front? not too terribly, but it is noticable. Now for the link/sync issue. I have read through Chris1956 suggestions and understand completely what he is saying,and he made more sense than the manual did. I have completed all the timing steps, however I think I may/know I made an adjustment error on the carb roller and cams. I will do the compression test in the am. as well as run the link& sync. My motor does sit pretty low in the water. Over the exhaust port until she gets moving. Is this an issue? Could I raise is somehow? The prop is the original 1958.13X13, I'll purchase a 14".

 

[Chris1956]

Re: 1958 Johnson Fat-Fifty Acceleration?

Do the compression test with the starter. Is the motor the correct length for the transom? A lot of those fattys were 20" (longshaft) motors and some of the 15 footers had 15" (shortshaft) transoms. That mismatch can affect performance. if the bow is digging in, move the tilt lock up one hole and retry. I think I used to use the third hole from the transom, as it was optimum.

If the spitter is underwater, that motor may be just too heavy for the boat. Be careful not to sink.

 

[PhilfromOhio]

Re: 1958 Johnson Fat-Fifty Acceleration?

I will move the notch up on the setting. I am pretty sure I have the long shaft. And I believe that you are correct, the engine mught be too heavy for the boat. I mean, when it is in the water the back of the boat is still about 6 to 8 inches out of the water, but when I am backing out some does back splash in, but runs right out the drain. I will make some link changes and more carb adjustments, but I may be fighting a losing battle if the motor is too much for the boat.

 

[PhilfromOhio]

Re: 1958 Johnson Fat-Fifty Acceleration?

Took the boat out today and ran 6 gallons of 32:1 mix. It is still really
slow to get going. I did however notice that it ran a lot smoother. I will try an push the mix to something near 50:1 and post results. Anyone have anysuggestions how i can get the hole-shot, so to speak, still verry sluggish and choky(a word i made up)...however once she's on plane I got roughly
28-30mph.

 

[Chris1956]

Re: 1958 Johnson Fat-Fifty Acceleration?

Is it possible that the two lower cylinders are not firing consistantly, while at idle, but fire properly at high speed? If so, this could be due to an incorrectly adjusted carb or a lousy carb. You might idle around a bit and see if the lower plugs look fouled, compared to the upper plugs. or maybe one bank has issues.

Those carb bbls cross over inside the intake manifold, if I remember correctly. So if the port cylinders look fouled, the starboard adjustments are wrong.

I used to run J6C plugs in the lower cylinders, and J4C plugs in the uppers. I do not know if it made any difference however.

 

[PhilfromOhio]

Re: 1958 Johnson Fat-Fifty Acceleration?

Chris1956:
Interesting. I noticed that when I was idleing through a no-wash area yesterday the motor seemed to be jerky. It woule go fast then slow. Definately a problem in the carb I think. I have had that carb off so many times. I have cleaned and re-cleaned, and adjusted those needles until I am blue in the face. I am heading out tomorrow to purchase a set of used carbs off an engine that was running great until he smashed the lower unit up. I noticed that one of my slow needles in mis-shaped. Ibought a new set of slow needles, but they seemed to mske no diference. I am wondering if the carb just isnt wore out?