MAKE SURE AND VARY THE RPMS BY 200-300 EVERY 10 MINUTES DURING THE BREAK IN AT LOW RPMS FOR THE FIRST HOUR.
2ND HOUR SHOULD BE 1500-2000 RPMS, VARIED EVERY 10 MINUTES.
3RD HOUR TO 10TH HOUR, PLANING SPEED, WITH BURSTS OF WIDE OPEN THROTTLE FOR NO MORE THAN A MINUTE OR 2.
I KNOW ITS HARD, BUT MAKE SURE NOT TO NEGLECT THE WOT BURSTS. IT NEEDS THE LOAD TO PROPERLY BREAK IN.
Thanks for the break in recipe, Chris. I knew I needed to follow a routine, but, did not know the recipe.
Re: the manicure, that’s the best I can do with a wire brush on a drill motor and pocket knife.
After a couple of hours of running around below 2000rpms and varying speed, pushed her slowly up on a plane. After a few more minutes, went to WOT. Think she had a fouled plug and she topped out right at 30mph. Throttled back to about 3500 rpm for a minute or two and she picked up the missing cylinder. With fire in all 4 holes, WOT was 37mph at nearly 5000rpms. 7mph faster than she’s ever seen. Hops out of the hole like she’s been goosed. I am convinced she’s been dragging a very weak cylinder for a long time.
So, I think I’ll pull the 16" prop and put the old 17" back on and see if she’ll push it. If she can make a little more speed with the 17" pitch, new power will likely be a new 90, rather than a 115 or bigger.
Excellent results. Well done!
“No bar, no pinball machines, no bowling alleys, just pool… nothing else.”
…well, some fishing too!
Why not try for another 28 years out of it! Glad to see you got it running right.
I can hear you yelling repeatedly…
WHO’S THE MAN!!!
All the way down here.
I’m smiling with you. Thanks for sharing.
Forget the 4 stroke…the fuel efficiency isn’t worth the maintenance.
if you are only seeing 5000rpms WOT with the 16 pitch prop, DO NOT CHANGE TO A 17
you would actually want to see 5500 rpms with a light load.
if anything you need to drop to a 15 pitch.
remember, the bigger the prop the more load you are putting on the motor.
Chris, spot on.
Figured I’d check to see if the laws of physics were still in effect.
That are.
With the 17" pitch, slower, but OK, hole shot.
Lost maybe 1 or 2 mph. Hard to tell with Saturday’s wind and current. Average of several runs in both directions - still hard to tell if the difference was real.
Max WOT rpm dropped to about 4650 - to low.
It is interesting how the slip number behaves. I get better speed at about 3600 rpms with the smaller prop. I didn’t expect that. Seems given an RPM, and foot gear ratio, and a prop pitch, you 'd be generating more thrust with the 17" than the 16". But, somehow, the 16" pushes her faster at that RPM? I’m missing something. Or, my data is bad. I see how fuel consumption should change. But, why is the lower pitch faster? Must be more to the different prop shapes than I was thinking? Diameters are different, also. Weird.
So, the smaller prop goes back on.
Found the timing retarded by about 4 degrees this weekend. Adjusted it. So, I’m hoping I’ll get a little bit more at WOT with the smaller prop getting it a little further above 4800.
Anyone know of any Johnson 115 parts from that era?
Might be fun to put the baby-butt exhaust cover and 115 carbs on her and see what she does.
Not really interested in spending money. But, I just had the exhaust cover and carbs off. Would be an easy swap if I happened upon some clean cheap parts.
Have you ever weighed the Henry O? What year is the hull? Something isn’t right.
The higher the pitch…greater distance traveled.
"One inch in diameter absorbs the torque of two to three inches of pitch.
Both pitch and diameter absorb the torque generated by the engine. Diameter is, by far, the most important factor.
Thus, the ratio of 2 to 3 inches of pitch equals1 inch in diameter is a fair guide.
Since top engine RPM is constant, increasing pitch means more speed. Then, why aren’t all propellers as small in diameter as possible, with gigantic pitches?"
The answer is simply that when the pitch gets too large, the angle of attack of the propeller blades to the onrushing water becomes too steep and they stall. "
Here is some more on slip:
THRUST AND SLIP
High-speed runabouts and fast cruisers require relatively low thrust and therefore operate at low slip whereas tugs and other heavy vessels require high thrust and therefore operate most efficiently at high slip.
If the boat were tied to a dock, the propeller would not advance at all but would generate maximum thrust because full engine power would go into accelerating water astern. This would be called operation at 100% slip.
Slip must not be confused with efficiency that is a measure of the percentage of engine power converted to thrust by the propeller.
We have seen that we must have slip in order to generate thrust and the amount of slip will be proportional to the amount of thrust required by the boat.
Since force (thrust) is equal to mass times acceleration, it would seem that we might get the same force whether we gave a large acceleration to a small mass of water (small propeller turning fast), or a small acceleration to a large mass of water (large propeller turning slowly).
In practice, however, there are other factors such as the relation of the propeller pitch to its diameter and the energy losses due to friction between the accelerated water and the surrounding water that make a proper rela
slip can make a huge difference, and slip changes at different speeds with different prop diameter and blade shape.
if you do find a donor motor, and want to see a huge improvement in throttle response and mid range acceleration, put in a set of composite reeds
based on the comment from mdaddy, there are a few flaws…
max rpm is not constant, so changing pitch definitely changes max rpm.
Propping is done by WOT as you know. Max rpm is constant…if all 4 cylinders are working correctly. As the pitch is increased, distance traveled and rpm increase…till the prop can no longer bite. It makes no sense that his rpm dropped going up in pitch only. IMHO.
thats the flaw in your argument…
max RPM is not constant.
if you had unlimited horsepower, max RPM would be limited only by the rev limiter.
You do not have unlimited horsepower.
changing the prop pitch changes the load on the engine.
think of it like riding a 10 speed bike up a slight hill
you are the engine.
you have a limited amount of power.
if you try to ride that bike in 10th gear, your RPMs are going to be much slower than if you change to 1st gear.
same engine, same bike, same hill, changing the gear( the prop pitch) will change the speed at which you can pedal (prop rpms)
Well, I got the answer(s) I wanted. Was that old 2-smoker actually running on 3 1/2 cylinders for its entire life? Yes. It was.
And, would a healthy 90hp motor (or, at least, this 88spl with 4 decent pistons) push that hull significantly better than a crippled one? Yes. Top speed picked up from just under 30 mph to about 35. I now know that I really think that hull needs a 115. 90 is adequate. But, just adequate.
Checked compressions a few weeks back to see what the new rings were doing having had some time to get seated. Holes 2-4 were still hanging around the 105-110psi range. The new piston/rings/honed cylinder were at 138psi. When I saw that, I liked the quality of the repair on hole #1 and, at the same time, knew that she would not tolerate that kind of delta across the compression numbers. Weekend before last, took the grand kids for a ride and noticed a slight plinking noise and said to wife, “That’s new”. A few minutes later hole #2 gave up the ghost. Slow cruise through Wappoo Cut headed to the landing and heard it happen. Could literally hear parts rattling around in the cylinder as it munched them up and spit them out. Idle rpm dropped and but she kept running and maintained a 25 yrs record of making it on to the trailer every time.
So, we’ll be restricted to the Bentz for a while. Will pull the motor off of the Henry O, clean her up good, do some cosmetic glass touch ups, and may disassemble and paint her. New power in the Winter/Spring time frame.
SORRY TO HEAR IT DIDNT STAY TOGETHER.
THATS A LOT OF WORK
Sad news my man.
The new ones won’t last as long as that one did. You’ll need a computer to find the electrical parts that fail that keep the “new” motors running. It is nice to turn a bolt and they don’t break though.
Best to you and thanks for sharing.
Can’t leave on such a morbid note…
This happened.
Over the Winter, put a new SeaCast transom in and hung a new Yammer Hammer 115. Have only tried to start her once when she was already running. The tell-tail peeing in the water is the loudest part (at idle… she makes noise when hauling a55).
Anyone interested in a parts motor. 1995 Johnson 88spl (LOTS (nearly all) of identical parts the the 90hp). No VRO. J88TSLEOC
Stator, coils, plugs, rectifier/regulator all replaced and probably have something like 30 hours on them.
Trim tilt works - replaced seals and motor years ago.
Foot unit works. Annual oil changes show a little fur on the plug magnet and the oil does show some very slight water intrusion, but, leak is apparently very slow. For about 10 years, I’ve just changed the oil and run her.
No idea if the block is usable. She definitely ate the rings in hole #2.
The entire thing has been disassembled within the last year to do the #1 piston/rings. So, all fasteners have been removed kinda’ recently. Should be able to get her back apart. Should… unless you can’t.
Control box, cables, and wiring harness intact and functional.
nice upgrade…
I repowered about 4 years ago with the first four stroke I’d ever run. I still try to start it sometimes while it’s running. But apparently there’s an override on the motor.
22 life’s a day
Haha I’m glad to see that.Enjoy the money you worked for,cause you ain’t gonna live to be 200.
Would my transom rebuild be interesting?
I think I took enough pics to tell the story.
If so, ill pull something together. Otherwise, why spend the time/effort.
What you waiting on…
22 life’s a day