Cooling Configuration on 4-108 Perkins

[jimisbell]

Got the tach repaired today and now I know that with no load the range of the throttle is 600 to 4000 RPM. It might have gone higher but at 4000 it was scarry so I shut it back down...#8-) Thats a start. On Monday on the way to the yard I will check max RPM with it in gear. That will tell something.

[Alan Wheeler]

You can also do it with reasonably accurate results with it tied up to the dock. Just make sure you are well tied up ;-) and open her up.

[jimisbell]

I think its reasonably tied up...BUT if it came loose I would rear end my other boat. That might not be easy to explain to the insurance company. Soooo, I think I will wait until Mondy in open water.

[SkiprJohn]

Aloha Jim,
Isn't 4000 scary in those 4-108s? That's why I just never ran my 4-107 over about 2800. Too much noise and vibration. Good luck on your experiments. I love a good mystery.
I'd kind of like to know a little more about your alternater/tach diode attachment. Sounds like something I'd like to investigate. I've got one of those one wire alternaters with only one post.
JohnL

[jimisbell]

Originally Posted by SkiprJohn

Aloha Jim,
Isn't 4000 scary in those 4-108s? That's why I just never ran my 4-107 over about 2800. Too much noise and vibration. Good luck on your experiments. I love a good mystery.
I'd kind of like to know a little more about your alternater/tach diode attachment. Sounds like something I'd like to investigate. I've got one of those one wire alternaters with only one post.
JohnL

If you can send me a picture of the back of your alternator I may be able to show you what I did.

Looking into the back of my alternator there was an opening in the case thru which I could see the ends of the diodes, solder covered posts sticking up from the circuit board below. I soldered a short wire to the end of the diode and that was the input for the Tach. I put a ¨push connector" on the wire so I could remove it if I needed to remove the alternator without cutting the wire.

[Andy Copeland]

The first indication that my overheating problem on the 4-108m was due to a faulty fresh water pump was several weeks after the rebuilt engine had been installed and several mechanics including the supplier were unable to solve the problem was a sudden loud squealing noise and the loss of the coolant into the bilge from the pump. A replacement pump was fitted and we were back in business with normal running temperatures.
Andy Copeland

[jimisbell]

Thanks. That seems to indicate that the pump which was new was faulty from the factory.

Well, we hauled Isabella today and the bottom was clean as a whistle but the prop was covered with all maner of growth in just 6 months. On the way over to the yard I found that the RPM was limited at 2000 which is just 50% of max RPM. Partly I am sure because of the growth, but I think the prop is also over pitched but wont know till I clean off some of the crud so I can read the specs on it. The cutlass bearing was pushing out and was worn substantually but I never had any vibration to indicate it. So after the prop is off it will get a new cutlass bearing.

I may not do the bottom job yet, I may just do the prop and cutlass bearing and splash it.

[Alan Wheeler]

Mate!!!!! you love holding me in suspense don't ya?? ;-)
Yep well the 2000 RPM is a good indicator something is wrong, but growth will certainly do that for ya. I strongly recomend polishing the prop as smooth as you can. The smoother, the harder it is for stuff to stick. If you don';t use the boat that much, then maybe applying Lanocote to it every six months will help you. If you do a search, we have discussed fouling on props and remedies in great depth. Although I don't believe there was any one true remedy we all rushed out to try. At least no one told me if they did all rush out. :-)

[jimisbell]

I have some EP-ZO vinal anti fouling paint that uses Zinc Omadine for the toxic component..no copper or tin...so its compatable with bronze props and it is for bottoms up to 30 MPH. At 900 shaft RPM the midpoint of the blade is going about 30 MPH...course the tip is going 60 MPH...#8-) I am going to try a couple of coats of that stuff for the first cut.

[Alan Wheeler]

Sounds good.

[jimisbell]

Alan,

Heres the data you have been wanting to hear.

I scratched the crap off the prop and it is a 20x18 that has been clipped to 19x18. WAY over proped. That is the overheating problem right there.

I will be pulling it off and get it repitched to 13 or 14.

[jimisbell]

Oh yes, the guy at the prop shop suggested that I donnt pollish it. He said he didnt want to sand it because "You dont have much metal there now, you dont need to remove any of it."

[SkiprJohn]

Aloha Jim,
Hope this is the cure. Please let us know.
Kind Regards,
JohnL

[hellosailor]

Jimis-
"You dont have much metal there now," You might look around, after the prop work is done, and see if there is a welding shop in your area that does "plasma deposition" or "flame spraying". This is a common and surprisingly inexpensive technique used to resurface large precision rollers used in printing and other machinery.
The shop uses a tool that is a cross between an acetylene torch and a paint sprayer, a hopper drops metal dust into the flame where it flashes into a plasma, which lands on your metal parts and actually builds up a layer of new metal on them.
There are many alloys used, chosen for hardness, durability, galvanic choices, etc., so you'd want to let the shop know you're looking for something that won't have galvanic problems. But...I'd guess $100 or $150 and you could have the whole prop, or at least all of the blades, flame sprayed and built up an extra 10 mils on all sides. And that's enough to put a nice polish on them, and still have more prop than you have now.

Or maybe something to leave until after you're sure this repropping is going to solve the problem.

[jimisbell]

I am qurious, do you think they could put coper over bronze so it would have an anti fouling surface? Bronze ciontains coper so it should be possible and a 10 mill coat of copper would solve the fouling problem as marine growth wont cling to copper. That would be worth $150 for sure!!!