Max prop setting

[Steve Murray]

Does anyone have experience with the settings on a 2 blade Max prop? While bringing the boat home from New Jersey, I experience overheating when running above 2100 rpm. With load, the engine would only reach 2200.

At first, I thought it was a heat exchanger issue. My experience with diesel engines is pretty limited. I let vinegar soak in the exchanger overnight, drained and filled again with coolant. No change. Finally removed the cooler ( after a yard in Vermont told me I needed a much bigger unit) but could see no clogging, scaling, etc.

I had the boat lifted and reset the 15" Maxprop to what correlates to a 9" pitch according to PYI.

I still only get 2400 rpm maximum but the boat will run all day at 2000 and 6.2 knots. That seems fast to me at that engine speed.

I would really appreciate some advice on resetting the pitch. I get significant vibration from 1300 to 1800.

Any help or diagnoses would be appreciated.

Steve Murray
E 35 III 222
Charlottetown PEI

 

[ted_reshetiloff]

You will find a lot of prop info on this site but the jist of it is that you want your engine to be able to reach max rpms per the manufacturer. Check the manual but I think you will find it to be around 2700. Too much pitch and you wont get the revs you need, too little and you wil rev to high and not get enough power. You want to make sure your tach is calibrated too. Have a mechanic set it with a stroboscopic tach. 2k is generally a pretty good cruising speed and 6.2 sounds to me about right assuming the bottom and prop were reasonably clean. I run a 2 blade max at 16 x 10.5 on my E-38. Cruise at 2k rpm at 6.9-7.2 max out at 2700.

 

[Loren Beach]

"You say you want a Revolution..."

Does anyone have experience with the settings on a 2 blade Max prop? While bringing the boat home from New Jersey, I experience overheating when running above 2100 rpm. With load, the engine would only reach 2200.

At first, I thought it was a heat exchanger issue. My experience with diesel engines is pretty limited. I let vinegar soak in the exchanger overnight, drained and filled again with coolant. No change. Finally removed the cooler ( after a yard in Vermont told me I needed a much bigger unit) but could see no clogging, scaling, etc.

I had the boat lifted and reset the 15" Maxprop to what correlates to a 9" pitch according to PYI.

I still only get 2400 rpm maximum but the boat will run all day at 2000 and 6.2 knots. That seems fast to me at that engine speed.

I would really appreciate some advice on resetting the pitch. I get significant vibration from 1300 to 1800.

Any help or diagnoses would be appreciated.

Steve Murray
E 35 III 222
Charlottetown PEI

Hi Steve,
Our '88 boat may have the same engine, the Universal M25XP, rated at 23 hp. Ours is rated to max out at about 3K rpm and cruise at 2400 to 2600. After several tries at setting the pitch on our feathering prop (two blade Martec) we do indeed cruise at about 6.2 kts and top out at 7.1 with a clean bottom. At WOT it does 2900 and that's close enough for me... heck, I really do not know how accurate the old tach is, anyway.

If you have the earlier version (M25) of this engine, it was rated at 21 hp, and I have no idea what the factory rpm reccommendations are. Others here will certainly know.

Harmonic Vibrations can occur in these little diesels at several different rpms. Even with new mounts this spring to replace the old shot ones, we still have vibrations at several rev ranges, but luckily not at 2500.

Best,
Loren

 

[NateHanson]

Sounds like you need to dial down the pitch another notch. Unfortunately it's a bit of trial and error getting the right setting, and you have to pull the boat to change the pitch (and even then it takes about one more thumb than I've got!). We went through this a number of years ago with a previous boat (Hinckley 38) that had a 2-blade max-prop, and I seem to recall that we somehow arrived at an educated/calculated guess for what the pitch should be. I don't remember if we did that by talking to a prop shop, or if we gleaned that info from the maxprop manual. Anyways, once we got it right, that prop really spoiled us. The reverse power is amazing. After using a max prop, all other props seem like egg-beaters when you try to go backwards or slow-down fast.

 

[Steve Murray]

Thanks for the replies. The motor mounts look good to me but the boat is still "in transit". I plan to get it into its own slip on the weekend and then will have time to spend some serious time in the cockpit locker.

I don't think I will be repitching until the fall since I can make the engine happy rather than myself for one season.

I am impressed with the Max, especially in reverse. I had a urethane Perfect Pitch prop on my previous Paceship 29. It was billed to have strong reverse and would "eliminate propwalk". Its performance can't touch the Maxprop.

Steve Murray
E 35 III 222
Charlottetown PEI

 

[Kim Schoedel]

Steve, we have the Max 2 blade. In the almost 2 years we have had the boat, I have not made any adjustments. With the 21 hp Universal, at 2k rpms we get about 6.2 knots, clean hull, no current or wind. If I push it to 2700 rpms, we get 6.8-7.0 knots. And we do get minor vibration at certain r's.

I have the original Max prop owners manual on the boat. I will try to remember to bring it home, copy and mail to you if you think it would be of some help. Might get to the boat this weekend so let me know if you would like it. If memory serves me correctly, I think there might be some hand written notes regarding settings.

 

[Steve Murray]

Thanks Kim,

I have the manual also and the adjustment guide is available on the PYI site. I'm sure you don't remember the setting on your prop but I went to 9.2 degrees in PYI speak. The old blade was in a box on the boat (15x11 I think). I was getting 6.2 at 1750 rpm with some black smoke and tried to approximate the 11 inch pitch.

I still don't know why I top out at 2400. This is my first experience with a diesel engine and the learning curve is very evident.

The 35 III seems to move very easily through the water; it carries its weigh in a very controllable fashion. I'm amazed at the manueverabilty in tight spaces.

Steve Murray
E 35III 222
Charlottetown PEI