Correct Prop for 1986 E32 ?

[newgringo]

Hello,
I'm new and in process of buying a beautiful E32. When we haul it next week I want to make sure the correct prop is installed for smoothest operation under power. It has a Universal MX25XP engine. What diameter and pitch should be installed? Any help is appreciated.
Thanks - Jerry email "griggs@centurytel.net"

 

[Glyn Judson]

Correct prop for 1986 E32

Jerry, I wish I were new like you but I'm pushing 63 F. But I actually I prefer to express my age now as 16.3 C. As far as determining correct prop pitch, read your engine manual to see what the maximun RPM should be. That number is what you should get on flat water and no wind with the throttle pushed all the way it will go. That IS NOT the speed you should operate the engine at though for any more time than an hour in the case of a Yanmar. My Yanmar 3GMF specs tell me that it should achieve 3,600 RPM. The cruising range for that engine is 3,000 to 3,400 RPM and should be adhered to in order to avoid excessive carbon build up in the exhaust elbow at lower speeds. Also check to see that there's at least 1" or more between the prop blade tips and the hull so as to avoid cavatation. So check your specs, do some measuring and see what you get on flat water. Armed with all that data, you can then intelligently approach your local prop shop should you need to change your pitch. Good luck, Glyn

 

[newgringo]

Glyn,
Yeah well I'm 18.5C. And I have a problem. This M25XP is rated at 23 HP at 3200 RPM. Flat out smooth water, no wind, it is only turning up 1800 rpm per the factory tachometer. There is no knotmeter but the boat is not making a bow wave and the wind speed meter (no wind now) is reading 4 knots. I have a mechanic coming to check the engine and tach tomorrow. We are all hoping it is just a fouled prop or something simple. But while it is hauled I want to be darn sure the prop is correct to prevent rehauling. Not to mention I can still walk away from this deal if I am looking at serious engine work. Oh, the joys of buying a boat.
Jerry

 

[Loren Beach]

My Universal manual calls for a cruising RPM of 2400 to 2600. Our prop is now adjusted to give us a bit over 6 kts in smooth water at these revs and will do about 6.8 at 2900. when throttle is against the stop.
Our engine has about 1800 hours on it, give or take.
The fixed two blade that came with the boat was over-pitched and the engine would hardly do 2500 and cruised at 1800. Do not assume that the pitch and diameter chosen by the prior owner or factory was correct...

We "straightened out" these issues when we put on the feathering Martec Autostream two-blade after a couple of years. AFAIK all feathering props have adjustable pitch and the brand we chose has this adjustment external.
Note that when checking out the existing prop, you are looking for a minimum tip clearance to the hull of 10% of diameter, and some books call for 15%.
After foolishly buying the same diameter as the stock prop and installing it, I discovered that I probably could have gone another inch in diameter -- always good for efficiency... oh well, live and learn...

There is a photo of our present prop on this site -- search on words 'prop options'.

Best,
Loren
Olson 34

ps: The separate engine survey I commissioned during the run-up to the purchase of our boat was the best $200. ever spent. The mechanic found an exhaust elbow problem that saved me more than his fee and I learned a *lot* about my engine.

 

[Glyn Judson]

Jerry,

Be prepared for the mechanic to tell you that your elbow is partially blocked, that being the most common problem to preventing top speed along with improper pitch.

That said, unless there's a lot of black soot emanating from the exhaust when at full throttle, it sure sounds like a case of over pitch to me. Is that 3,200 RPM the maximum allowable speed of the engine under load or just the point at which it delivers the most HP? The number you want is the maximum RPM while under way, perfect conditions, etc. Good luck with the mechanic tomorrow, Glyn

 

[newgringo]

Well we still don't know what the correct prop is but the mechanic blessed the engine as A-OK (started up good in 25 deg F too!). Two apparent reasons for low rpm are barnacles on prop an an obstructed air intake (improper crank vent hose routing), as well as a dirty hull. When this is all done I'll report back with prop and performance info. Thanks to everyone for suggestions and advice. Jerry

 

[clayton]

prop for '86 E32

The 2 blade fixed Martec on our '89 E32-200 is a 15" D x 11 P. Cruising rpms typically 2500-2800.
Clayton

 

[newgringo]

Follow up data, but not done yet. Got all the barnacles cleaned off the prop and shaft and cleaned the bottom. Yuk. As mentioned before this is an 85 E32 with a M25XP with 2:1 reduction. The prop is a 15" dia X 11"pitch. It clears the bottom by 1 1/4 inch. Now as for performance the engine now turns up 2250 rpm but that is with boat heading directly into a 30 knot headwind. My GPS was measuring 5.8 knots. So I still don't good data but I still think I'm a little over propped but will wait for some more data and advice. What do you guys think?

 

[jgarmin098]

I have an '88 32-3 with the 25XP. The prop is a fixed 15x11. Max RPM is 3200 ish and cruise is 2200 to 2400 at about 6.0 to 6.2 snots. It sounds to me like your set up is nominal. I'd stick with it for the first season. That was the advice I got 8 years ago and never felt the need to make any changes (except, of course, I still dream of strapping on a brandie new two blade Max Prop).

 

[ted_reshetiloff]

5.8 kts into a 30kt headwind sounds pretty good to me for a 32 foot boat, unless of course you had 5kts of current pushing you along

 

[newgringo]

Nope. No current to speak of. Slack tide in an inland bay. And yessiree it was a blowin. Lots of spray over the bow. Thank God for a good dodger. And all of us thought it was jusf nifty. I am going to get some good speed and rpm data on smooth water soon. More realistic.
Jerry

 

[JORGE]

On the Prop subject

I have an older 32-2( 1971), installing a Yanmar 2 gm20 and the new shafting is 7/8" and I will be needing a prop, the original 12" two blade is not going to do it. A quick measure indicated that I may be able to fit a 15" blade and still have about 1.25" to top of hull, whereas a 14" blade would leave me with a 2.25" clearance to top of hull. A prop company called A1 suggested using a 15x10 or 14x12. Is there anyone who has gone through this? Is the 1.25" top clearance okay, or is this too narrow?


On the subject of engine beds: mine are fabricated birch ply laminated beds, (the "original " steel mounts were almost completely rotted, and the old Atomic 4 would have caved right in.)
I ended with Yanmar mounts for the engine front and actually found that the rear mounts made by "bushings" company, sold by Mack Boring & Parts in New Jersey worked well since they provided about
2.5 " of lift at the back of the engine. The company offers a catalog and good tech support. The original rear Yanmar mounts are useless to me and seem to be in sound condition.

 

[clohman]

I purchased a Campbell Sailor 3-bladed prop for our 1986 32" with Universal M-25. The hull speed at 3,000 RPM increased from 6.something with the original 2-blade to 7.2. It doesn't back as strongly as the 2-blade but is alleged to have less drag. Prop walk is nil. Vibration is reportedly lower, although I replaced the cutless at the same time so I'm not sure which contributed to the reduced vibration.

 

[newgringo]

End of the story, finally. I am now repropped with a new Michigan 3 blade sailor prop of the proper diameter and pitch. After first feeding what I thought was good RPM, transmission ratio (advertised 2:1) and boat speed test data to Jon at THE PROP SHOP in Mukilteo, WA he said something was goofy that the numbers did not make sense. Time to get serious. Double checked the Tachometer calibration and found it to be off 300 rpm (14.5%). Also discover the Hurth Transmission had been changed and the actual ratio was 1.8:1 NOT 2:1 as in the literature. Finially I discovered the engine is an M25 (21 HP) NOT a M25XP (23). Now the data made sense. We put on a 3 blade of smaller 14 inch diameter for proper hull clearance and 8 inch pitch targeting for a full power engine rpm of 3000. The in water test data yielded a full power RPM of 2955 at hull speed of 6.8 knots. Best of all is the very smooth operation. The old hull vibration from the 2 blade (15 X 11 P) is gone. All told this adventure cost me $364 for the prop at my door and another $75 for a diver to install it. Some of the best money I ever spent. Now does anyone know how to adjust the tachometer so it will read correctly?

 

[Tom Metzger]

Tach calibration

Now does anyone know how to adjust the tachometer so it will read correctly?

This is from the teleflex sheet on their diesel tach. It can be found on their website also:

7. If the number of alternator poles is not known, measure the actual RPM with a Master Tachometer. Rotate the selector switch to the letter that puts the tachometer closest to the actual RPM.

Final Calibration adjustment requires the use of a Master Tachometer. Connect the Master Tachometer and start the engine. At about 1500-2000 RPM, use a jeweller’s screwdriver to carefully adjust the potentiometer in the
“CAL” hole (about 10 o’clock on the rear of the tachometer), bringing the tachometer into agreement with the Master Tach. Only a minimal amount of turning is required. Over torquing of adjustment will damage gauge mechanism. Turning clockwise increases tach reading, counterclockwise reduces reading. If the tachometer cannot be brought into calibration, the black Range Selector Switch is probably on the wrong setting.

8. Alternator belt slippage will cause some error on the tachometer.

 

[newgringo]

Tom,
Super! Thought there must be some way to tweak the tach. My belt is reasonably new and adjusted correctly. Very sure it is not slipping. Will be adjusting this week.
Thanks-Jerry

 

[newgringo]

Tom,
Done. Got the tach dead nuts right on (at least as close as I can read standing on my head to see it). Had to move the selector switch to a lower number then fine adjust. This web site is GREAT. Has helped me as a new sailboater so much. Can't wait to get things squared away above deck and GO SAILING. Soon!
Gerald Riggs