Shaft Seal - This Could Get Ugly...

[Kanani]

Originally Posted by markpj23

I pulled the compression housing back away from the stern tube seal and found everything to be in good shape. I should note that on the trip to the yard we did not leak a bit.

I've also removed the static portion of the seal from the stern tube hose and slid that forward. There is some calcium build-up on the shaft but nothing looks amiss. I will clean it all up with some emery cloth (not the seal surfaces of course), wipe the carbon seal surface clean and reassemble.

I think all I had was some critter contamination.

Shaft looks fine. Had the cutless bearing replaced and got 2 different mechanics recommendation to leave things alone as they see no issues.

Regarding the black smoke, I'm becoming more and more convinced that I'm over-propped and have been since we bought the boat.

Some days during the refit are better than others....

I'm glad that all is OK.....I was beginning to get concerned.

If she is over-propped, that will become quite evident when you put her back in the water.

With a nice fresh bottom job, you should be able to motor at the maximum rated RPM for your engine. If you cannot achieve max RPM, make a note of the RPM and boat speed (in calm air). Take the prop off and get it re-pitched. It may not be necessary to buy a different prop.

The ideal is to be able to achieve max RPM and no more. I have seen people post on here that you should have "Reserve". Consult your prop specialist when re-pitching (if necessary). I think that he may say different.

Having the ability to "Over-rev" the engine serves no purpose and can damage the engine. To get the maximum benefit from your engine, you need to be able to utilize the maximum HP. The max HP is usually achieved at about 10% below the max rated RPM. By having an engine able to spin 10% faster than maximum rated HP will lose you the effectiveness of that HP by about 20% when you need it most (heavy conditions).

If you cannot achieve max RPM, the effect is even worse. During calm conditions your engine has to work harder to achieve that same push (thus black smoke) and you fall way short of needed HP (as much as 50%), on the lower end of the scale during heavy wind and seas.

[Charlie]

Hi Mark:

Glad to hear that something in the boatyard let you out cheaper or at least with out taking a big bite out of your wallet.

[markpj23]

Originally Posted by Charlie

...Glad to hear that something in the boatyard let you out cheaper or at least with out taking a big bite out of your wallet.

Amen to that!

[Kanani]

Originally Posted by markpj23

There are some variations in the shafting arrangement apparently. Here's mine when first hauled last year - before clean-up (yuck!) I have a single strut supporting the 1.5" shaft. Heavy steel backing plate supports it under the aft berth.

No I've never wrapped a line on the prop - knock on wood...

Mark,

I just went back and looked at this pic........I'm pretty sure I know why you were blowing black smoke. I'll bet it doesn't do it after you cleaned that prop up all nice & perdy...... That was like trying to turn a concrete block through the water.

I learned a trick in NZ....I put lambs grease on the prop (can't recall the actual name of the product). Kept the growth off for quite a while. It can also be applied under-water.

[Beemer]

By the way, that pic of a stuffing box hose looks to have been caught on something and ripped..that's not what a cracked hose will look like.

Seriously, look at the picture. The angle of the tear doesn't follow the angle of the nylon wrap in the hose. Plus, if you save the pic and blow it up, you can see where the snag actually caught, came loose and caught again.. Looks like it was snagged from the middle and was twisted to the right, since the attaching clamp (hose clamp) hose protector (the dark black thing under the two hose clamps) is actually COVERING part of the tear. This is the same type of nylon hose used for exhaust connectors for thru-hull exhausts and also for turbocharger and intercooler connections as well as for Farm Tractor radiator hoses. It has around 3 layers and is the equivelant of having weather checks on an 8 ply mobile home tire sidewall. The first ply is cosmetic. However, if you can insert a screwdriver PAST the first layer or two..then you replace the tire. Since these have zero positive pressure (unlike when they're used in radiator and turbocharged applications where they see 30 PSI and HEAT, they rarely disintegrate unless exposed to fuel or oil.

Also, oddly enough, hoses seem to deteriorate more from the inside OUT when exposed to heat, since engine heat will hit the inside of the hose first.

How many engine hoses have you changed in your car that were torn up internally but looked decent on the outside? I race and have for 30 years or more, and I've yet to blow a radiator hose from an outside scuff like that.

The outer nylon wrap is there just for that reason too, to protect the hose. I wouldn't say that the hose in the pic doesn't have internal damage from that scuff that happened over time, but since the area isn't pressurized much, or tremendously hot, like a radiator or heater hose is on an engine, I seriously doubt it was anywhere near failing.

That's like having your car mechanic say you need new brake calipers because you have a weather cracked dust cover on your caliper puck. That dust cover has NOTHING to do with sealing the caliper..but it DOES keep dirt away from the internal seal..but you can simply wipe a coat of black RTV around the dust cover to fix any minor cracks. However, if you drive in any heavy dust, rain, snow, etc, and the dust cover is missing, then you get a new dust cover and install it, but you don't need a new caliper unless you're losing brake fluid thru the seal or the caliper puck is stuck.

Oh, and if you own Michelin tires, they have a tendancy to dry out a bit faster than other brands. However, if the tire dealer tries to sell you new tires, yet your tires have nearly new tread (especially trailer tires that weren't covered) you can simply swap the tire around on the rim..the rear facing sidewall usually IS NOT cracked because it has been protected from UV exposure.

Believe it or not, I've had RV guys tell me to slather a bunch of SPF50 sunscreen on the exposed sidewalls to keep them from suffering UV related deterioration too.

Anyway, the big part of any hose is the inside of the hose..especially if it is a multi-layer hose. If the inside gets soft, THAT will allow a blowout. Just like if you have a bubble in the sidewall of a car tire..That's a BREACH of the inner surface..sort of like a hernia. THAT needs to be replaced asap.

Just my two cents from 30 plus years of auto racing.