1962 28h johnson info

hello all, Id like some info on how(if any) I could get some mph out of a1962 28h johnson. First I should add that its compression was 80-85. low I know but I think the alum prop is not kosher. Its dinged up and looks in need of replacing. I cant seem to find a pitch # on it either maybe its behind the plastic cap? My question is if I could gain 5-10 mph by going up on pitch or is my comp. too low to gain much? It starts ok but doesnt seem to be revving a lot. No tach so its hard to tell. The motors on a 1983? 15ft sea nymph open bow alum. 19mph is kinda slow to get to the other side of the lake, but its still better than nothing. I would like to have it returned to (like new) someday as it is a great motor, but just not this year if I can get one more summer out of it. Im kinda new to this so any help would be great. thanx. bouttime007

Re: 1962 28h johnson info

there is no way you are going to pick up 5 - 10 mph by changing the prop. read the 2 decarb post on this link, and do it. may help free up the rings, and get the crud out of the engine so it can perform better. the size of the prop is stamped on it behind the cone or the other side. your lucky it's running as well as it is with that compression.
http://forums.iboats.com/forumdisplay.php?s=&f=31&page=1&pp=50&sort=lastpost&order=desc&daysprune=-1

Re: 1962 28h johnson info

You wouldn't get another 10mph out of that 28 if it were brand new.

Re: 1962 28h johnson info

Howdy, bouttime.

Welcome to iboats.

Your engine is definitely not performing up to snuff. A 9.9 should be able to move your boat that fast.

Are both cylinders making power? Pull each spark plug wire when she is at idle and in neutral. If rpm don't drop that cylinder is not making power. You should be able to get a 7/16" arc to the block from both plug wires.

Is the timing right? Do a "link 'n' synch" by the manual.

Is she carboned up? Do a decarboning by the instructions in the Engine FAQs.

Correct fuel mix? 24:1, 1 qt. TC-W3 oil per 6 gallons 87 octane unleaded.

Correct spark plugs? Champion J4C gapped at .030"

Correct point gap? .020"

Correct prop? Get or borrow a tachometer and find out what your WOT rpm is under load. Select a prop to get about 4500rpm.

My guess is that you are lacking spark to one cylinder and may also have some carbon to get rid of.

Good luck, and let us know what you find.

Re: 1962 28h johnson info

Well it was worth a shot. Is it pushing too much boat for the low comp? Theres a shimmy at 1/4 throttle, I figured the prop was bad. Thanx again.

Re: 1962 28h johnson info

The feul mix is right, had it wrong last year when I 1st put it in the water. I do need to get a tiny tach tho(1 more thing I learned from this forum). The cowling says the points, plugs and condenser were replaced july 96 maybe its time for another tune up. My plugs are champ. rj12c . not right? The decarb sounds like a plan, thanx. Yep prop #s were behind the cap it says 101/2 x 12. sound close?

Re: 1962 28h johnson info

RJ12C is for a Chrysler Imperial, Dodge Coronet, a few industrial engines, a few non-OMC outboards, etc. Someone must have just had them laying around and decided to use them. A 10 1/2 x 12 prop is about right. Your 28 is just a '56 30hp incarnate and std. prop for it was 10 3/8 x 12 1/2

Re: 1962 28h johnson info

Try RJ6J plugs in that boat or just J6Cs. Check them after a full throttle run. If they're really white, switch to J4Cs or RJ4Cs. What you have in there is way wrong.

Yes, it's time for a tuneup. And if the prop is dinged up, that could well be part of the problem.

As for your compression, it's not horrible for that old design. Once the thing is running right, though, it'll probably go up. Anything over 90 psi is fine.

Dump an entire quart of Seafoam in a 6 gal. tank of fuel/oil mix, at 24:1.

Your prop is probably close to ideal in diameter and pitch. 10 1/2 X 12 should be about right. The 35 hp version of that motor did best with the 10 1/2 x 13.

Check your throttle settings. With the controls wide open, the throttle butterfly should be absolutely vertical in the carburetor. Get on the lake, and run wide open, then in small increments, screw the high speed adjustment in 1/8 of a turn at a time, waiting to see if the engine speeds up. At some point, you'll lean it out too much and it'll sneeze or run rought. At that point, back of 1/8 of a turn and you're set.

Next, fool around with the tilt settings. You may run faster with the motor tilted in or tilted out. Try it, one notch at a time.

You should see something between 20-25 mph with that motor, on full plane and with it running around 5000 rpm. That's the best you'll get.

Re: 1962 28h johnson info

Ok, that is a help on the plugs thanx. I checked laingsoutboards and the prop theyre selling my year & horsepower is the 10.5 x 12 so I guess Im ok . Im gonna get new one. (and J4C plugs) Im gonna run some seafoam thru it also. Im sure itll help. Maybe the comp. will increase by a few by freeing up the rings? Just to check: the freezeplug on top of the motor has the #s 2303245 on it , does this denote a "62 28h? There arent any other plates or #s that I can see. Im just going by whats enginepenned in the cowl. Would a rubber cowl gasket fit from a 33h or 40h from 1962-66? Just wondering.

Re: 1962 28h johnson info

To JB,I fixed the wot problem last year cuz it wasnt getting all of it. It was a chore getting the 62 to be compatable with the newer boat.The steering was a pain to match. Also I gotta pick up a manual (or check the library) As for the tilt I did move out 2 notches last year, which helped ALOT. Theres 1 more notch left but I think Im pretty good there. I had the motor checked at the shop before fitting it and was told of the comp and that it may start hard. Which it doesnt, it runs great just alittle slow to plane. Ill check the HS jet when ice-out comes (in a week or 2 hopefully) and I can put her back in.

Re: 1962 28h johnson info

Well a little over 2 months and I finally got to wet the boat.(dont ask) I put J4Cs in the old 28 and ran some seafoam through the tank, didnt get to squirt it into the carb though. (my squirt bottle decided not to squirt when I got to the lake) It perked her up a little bit after an hour, and seems to run even smoother than before. It was too rich also, so I leaned it out untill there was no more adjustment left, but it was better. Once I can get back to the lake I can squirt the seafoam into carb and plug holes for the full treatment. I only put about 6oz into 3 gal of feul, so I didnt see much smoke-but some. I will post the full end results of the decarb when done. Still have that quarter throttle shimmy though, still in need of a new prop.