How to remove crank protector from 1973 25ss

[zul8tr]

I have my 1973 25ss engine apart and the bottom crank seal needs to be replaced.

Question - In the attached figure how do you remove the pressed on steel driveshaft protector cap at the crank bottom? Is heat the answer?
This cap is about 0.060" greater OD than the crank OD and the extra thickness seems to prevent the seal from going on . Off is easy if the seal is damaged, so what as long as I can get the correct seal to replace. Also there is a rubber O ring in the tip of this cap that seals on the drive shaft when it is installed.

Thanks.

 

[Chinewalker]

Re: How to remove crank protector from 1973 25ss

I've simply pulled them off - gently. A crescent wrench tightened down to the diameter of the crankshaft may help tap it off as the edge hits the lip of the retainer.

We don't see many 25SS Mercs on i-boats. I've got a pair of them that I've run quite a bit. Mine are both 1980 models, last year of production.

- Scott

 

[zul8tr]

Re: How to remove crank protector from 1973 25ss

I've simply pulled them off - gently. A crescent wrench tightened down to the diameter of the crankshaft may help tap it off as the edge hits the lip of the retainer.

We don't see many 25SS Mercs on i-boats. I've got a pair of them that I've run quite a bit. Mine are both 1980 models, last year of production.

- Scott

Thanks for the tip I will give that a shot with the addition of PB Blaster. I have had this engine since 1973 when I purchased it new from **** O'Dea. I raced it in 25ssh in Region 5 from 73 to 80 using friend Harry Pinner props. Here is a pic from 1978 out front in Lake Worth Fl in my home built and deck modded Hal Kelly Wetback. At the time the basic design was 1955'ish and still competed very well with the up to date stuff.

What was changed from 1973 to the 1980 version? When I was racing this engine the speeds I was running in the 1970's (63-64 set up for heat racing) were up to the later models so that's why I was asking.

I was not in racing when the loop charged 25XS came out but would have been pissed since it caused the demise of the deflector charge 25ss.

 

[Chinewalker]

Re: How to remove crank protector from 1973 25ss

The only differences I've seen between my 25s and the earlier ones are:

> In the mid-section - mine has a small round relief snout, not the slotted relief that tended to be a weak point. That's why most, if not all of the early 25SS motors have plates welded onto the mid-sections on either side of the exhaust relief outlet.

> Updated ignition components. Mine have the later plastic housed CDI box and the black plastic housed coils.

I bought mine from the original owner. He bought a pair of them in 1981, directly from Mercury in Wisconsin. One was blown when I got it (he ran it 50:1!) and the other has never been apart - might have 3 hours on it. I rebuilt the blown one with new pistons & rings and have run that one a lot. Raced it a few years in Classic B Runabout against 20H conversions before I put my own 20H together.

- Scott (112-N)

 

[zul8tr]

Re: How to remove crank protector from 1973 25ss

I finally removed the cap. Turned the crank cap pointing up, filled the spline socket with PB Blaster and let sit for couple days. Then used a blunt set punch and also cresent wrench you suggested and tapped on the thin edge around the circumference a bit at a time. Mild rust was the culprit.

I have some questions about your 25ss engines:

How did the 25ss compare in speed and acceleration to the 20H conversion when you raced classic B?

What type and make classic B hull did you race?

What advance degrees are the magnetos set at? I have been using 40 degrees (0.315") The factory tag suggested 38 degrees at 6600 rpm. I ran it at 7000 - 7100 so it required a bit more advance.

What crankshaft end play did you set the rebuilt 25ss at? The data sheet that came with my engine states .003 to .010".

What compression (cold) psi do you have in each engine? The 25ss are low compression (9.2:1) compared to the 20H (10.5:1). I get 115psi cold.

Do your engines have the 0.012" thick reeds and longer Merc 200 reed stops to prevent reed tip whipping and resultant reed tip damage? This was the first change I did in APBA racing in the 1970's and they recommended it in the inspection manual.

Thanks

 

[Chinewalker]

Re: How to remove crank protector from 1973 25ss

Top speed-wise, the 25SS compared quite favorably to the 20H conversion motors, but the 20H had quite a bit more kick in the behind when coming out of the turns.

Here's a few pics of the boats I ran the engines on....

The ones with the 20H Conversion: It is a 1980s era hull out of New Jersey (basically an Austin copy, bowling alley chine, etc.), originally built for the Mercury Challenge Series (a for-money series of races Mercury sponsored in the 1980s) in 25SSR and was run with the 25XS Merc. It's about 10'6". I built up the transom to fit the 25SS/20H transom height. I raced the class for fun as I wasn't very competitive - I'm not really cut out to be a B/25 driver at 6'4" and 240 lbs. I get about 54-55 out of it, but guys I've lent the boat to can get a bit more (they're a better fit for the class at around 150-170 lbs.)

The ones with the 25SS: Is actually my C-Runabout. It is a Broccoli, built by Craig Bowman. This was the only hull I had my rookie year and I wanted to run a second class. Classic B has a minimum hull size, but nothing about a maximum! The 25SS actually performed quite well on the bigger (11'6") hull. It was a little slower, but I wanted the seat time that year, so I ran the extra class - in the rear, with the gear, as they say.

As for the technical questions, I'm afraid I can't really help you much. I didn't change anything on the one I rebuilt - just swapped out the scuffed piston, honed the bores lightly and reassembled it with new rings. I remember looking at the reeds to see if they were cracked or chipped, but never did anything beyond that.

I've never gauged the compression on either motor. The timing is set high enough where they will kick on you if you don't pull it like you mean it. I'm sure you're familiar with the 25SS handshake - fingers cramped in a curl because you had the handle ripped out of your hand!!

- Scott

 

[zul8tr]

25ss etc.

25ss etc.

Looks like a nice time with those runabouts. Good looking rigs. Are you still actively running these? I only raced hydro in APBA in the 25ss and 20ss (Yamato Y80 engine) class. The Yamato was a real accelerator and a handfull and a bit faster top end than the 25ss. The runabouts look like alot of fun. I will be getting a chance to run one at a Florida meet in couple weeks at the Antique Outboard Motor Club. It is a Hal Kelly Airborne hull with a Mark 25 mated to a 20H tower and 1:1 quicki gear case .

Thanks for all the info.

Pete

 

[Chinewalker]

Re: 25ss etc.

Re: 25ss etc.

H Pete,
I raced from 1997 to 2001. I still get the Broccoli out every now and then with an old Mark 30H to pound my knees a bit...
- Scott