Prop size ?

[bonz_d]

The set up is this; 14' Lund DLX with side steer console and a 35hp Evinrude. Total weight with me in it appx. 600-650#.

Just purchased the motor and ran it for the 1st time last weekend. Got it up to about 1/4-1/3 throttle and it started slipping. Got it back and removed the prop. Found that the prop on it is an aluminum 10.5x11 and I thought that it was spun.

Located a local prop shop that had an 11x9 aluminum that was brand new and had been sitting on the shelf for awhile and they offered it to me for a very nice price. They also have a basically new SS 10X13 that they offered to me for $150.00. They asked me to bring in the old one to look at and when I got there he explained that the prop was not spun, it was just used up. Reworked to many times and was basically now a 9" diameter and to small.

I bought the 11x9 and ran it Friday with just me in it. Boat came up on plain very quickly and just flew. Today I ran it with 2 of us in it and it preformed almost the same. Was/am satisfied with the performance.

Tonight I was on Michigan Wheel site and found that they are reccommending a 10-1/8x14 or 10x15 aluminum or 10-1/8x15 SS for a 13'-15' boat with all loads and the 11x9 for 17'-20' boats.

The motor sounds like it's running normally at WOT. Not struggling or over reving but there is no tach to know for sure. So should I trust Michagan Wheel sizing or the prop shop that tells me this 11x9 will work very well on this setup? What should I expect if I change to the 10x13 SS or a 14 or 15 pitch? Remember this thing is flying as is and not really looking to go faster.

 

[steelespike]

Re: Prop size ?

Actually without the rpm and speed its difficult to know exactly where you are at. What year motor?My 89 aftermarket ser. manual indicates the 76-89 35s rpm range is 5200 to 5,800 rpm.The 11 X 9 does sound a little light though the almost 1" increase in diameter could reduce rpm some.But at 9" I'd be a little worried about overeving.The 81 OMC prop guide indicates the 9" is for 16 to 18' heavy loads,11" heavy runabout/skiing,13" general use.So your pretty far out.You could get a Tinytach they are reasonable easy to install and will fit any similar motor withouit regard to stator poles.Then borrow or buy a GPS and you'll be golden for getting the ideal setup.I would stay away from wide open throttle until youi know your actual rpm.

 

[bonz_d]

Re: Prop size ?

Thanks for the reply and sorry for the delay in getting back but right after I posted this question my computer took a dive and just now got it back.

Will have to look into that Tinytack, though as I stated before the motor does not sound like it's screaming at WOT with 2 people in it. Also wouldn't a steeper pitch increase the top end speed? Don't know that I need to go any faster than what it is.

I have sense talked with the guy at the prop shop and he suggested stopping by and trying that prop and if I didn't like it I could return it. Would $150.00 be a lot of money for a slightly used SS prop? It still looks brand new.

 

[steelespike]

Re: Prop size ?

Stainless props are expensive and they usually do a great job all around.
You might look up new aluminum and stainleess right here at iboats see what they are running.The whole idea in prop selectiopn is to heve the motor operte within its recommended rpm range.Of course you can't tell without a tach.The ideal prop will usually produce the best speed and economy and put thge motor at the correct rpm.Perhaps you could borrow a shop tach?
By all means try the prop.It should make a huge performance change it may not get up as fast but if it seems to perform well it probably is close to correct.But without a tach it is a crap, shoot.Also would be very good to have a gps speed.