Prop ID question

[Jack Daniels]

I have a 83 85 HPchrysler FORCE and i was curious about the pitch of my prop. Stamped on the side is a 526-21, does this make sense or and i mis reading it.

Also if this is true, does that make the prop a 21 pitch. That type seems kind of high for a 85 HP, plus when you add that I am running at 6000 rpm at wot it doesnt make sense.

One more thing, if this is a 21 pitch then would it be safe to assume that the tach is incorrect or the rectifier needs replaced. WIth that high of a pitch common sense would dictate that my RPM would be lower. Thanks for the help.

 

[steelespike]

Re: Prop ID question

Max rpm and speed would tell more.gps speed is best.Of course 6000 doesn't make sense.A brief check of the net and iboats didn't produce anything
although 19" was the highest listed 15 was lowest.A prop shop should be able to tell the size.

 

[Frank Acampora]

Re: Prop ID question

That prop was made for Chrysler by Michigan although Michigan did use that profile for some SPM (Mercury) props . In my opinion, that style prop is the best readily available prop for a Chrysler.

The 526 is Michigan/Chrysler number that defines the prop style and pitch. 21 IS the pitch. Unless you are running the 85 on a 14 foot boat I doubt very much if the engine is turning 6000 with that prop. Check to see that it has not been cut down. Diameter should be 13 -13 3/8. If it is significantly less than 13, that's why you are turning 6000. Blade profile should be rounded ears with a straight leading edge. If the leading edge is curved significantly with relatively pointed blade ends, It has been repaired by a lazy prop shop that only ground the leading edge to remove damage, not built up by welding. This also reduces blade area and could lead to higher RPM, however, an 85, ESPECIALLY a 1983 85 with the small bore pistons (3.3125), should not be able to turn that prop anywhere near 6000. If there is any number stamped into the outside of the hub other than 526-21, then it has been repaired.

Those props were manufactured in 15 17, 19, and 21 pitch. Never saw the 15 pitch but 523 is 17 pitch and I think 524 is 19--but don't quote me on that one. Memory is the second thing to go with old age. 510-19 is the stainless 19 pitch. Very well made prop with beautiful lines and great performance on a Chrysler or Force. Actually seems to run better than the stock Michigan branded props for Force.

Believe it or not they did make a rare 529 25 inch pitch. On that one, the blade roots stick out about an inch past the hub. LOOKS RADICAL! I don't usually run it because it has undesirable torque reaction on my small 14 foot go-fast boat and because it is aluminum. BTW a 1988 Force 125 turns a 12 X 21 cupped stainless cleaver prop at 5900 on that boat for something around 60 MPH. So: if you aint doing near 60, you aint turning 6000.

Don't go all over the forum--ask Frank first! I am a fountain of useless trivia that just SPEWS forth unbidden.---Thank you, you're welcome! LOL

 

[Jack Daniels]

Re: Prop ID question

OK frank as usual you are dead on. the prop is a 13x21 per prop shop. I currently have it in for repairs. So the next question is my TACH off, how do i figure that out, or should i just replace it, they are cheap. Thanks

 

[Weber67]

Re: Prop ID question

Hey Frank, maybe you can help out on my prop?

There is a thread posted, I sure would appreciate any help!