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I got a 13.25x15 for my 88SPL and it came with a hub kit, but no instructions. The black hub is pretty easy to figure out, but there are also two washers, one large and one small. The large one appears to go behind the hub, likely on the shaft before putting the prop on, but it it has a ridge machined on one side that is a smaller diameter. Not sure which way it goes on. The smaller washer is not machined, but stamped and there is a ridge on that one as well. Assuming it goes over the hub, but it could fit inside the prop as well. Anyone install one of these props?

I'm looking to get out this weeknd to try it out. Surprised they did not provide instructions...

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Hi Larry,

There should have been some printed instructions with that kit. Let me ask: are there two washers *in addition to* the thrust washer? Or are you describing the thrust washer AND another conventional washer?

In all cases, all outboards, all outboard brands, there is a thrust washer which is very large and thick. You already have one with your current prop. You put this on the prop shaft first making sure the tapered hole matches the tapered prop shaft's shape.

The hub insert goes in the prop and the prop goes on the prop shaft.

Now there is usually a spacer and/or washer that precedes the prop nut. The purpose of this spacer is to place the nut where the prop shaft is threaded and to prevent it from "bottoming out" before it cinches up on the prop.

The thin washer usually prevents the nut from marring the prop. In some cases the spacer serves this purpose as on most Mercury outboards.

If this is not clear enough, post a photo of what is in the kit and we'll go through it part by part.

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Thanks for the reply, I did get the prop on Friday night.
There were two washers, one is the thrust washer, the other was stamped with a #3 on it, but no other markings. I just was not sure about the placement of that one and the orientation. The hub insert was very tight going into the prop bore. I used a block of wood and and shot filled hammer to drive it in, although it never did bottom out against the prop itself. When I went to install the prop nut, I had to crank the insert in further to get it to line up with the cotter pin hole. I did an overnighter on the delta for sturgeon, and got to run some rough testing in different water conditions. We had 15 knot winds pretty much all day in the bay, so a pretty good wind chop was out there. I noticed the prop does bite better in the chop and the holeshot coming onto plane feels like it is quicker. Later in the day, I went into a slough and found some flatter water and ran up to WOT to what she did. Top speed with 15-18 gallons fuel, myself, (180#) and fishing gear, topped out at 39.7 mph GPS speed. It was very surprising to see that WOT RPM was an indicated 4800 RPM. The old prop is a BRP 13.25 x17 aluminum, and top speed is at 39.1mph at 5300-5500 RPM WOT. I have no reason to suspect the tach but it did not “feel” like 4800 RPM, it did feel closer to the 5300-5500 range I am used to. Not sure why this is happening. Motor is running as well as ever, de-carbed it two weeks ago, it feels very strong from idle to WOT.

I’m worried about the 4800 RPM number. If this is a correct number it indicates to me that I’m over propped. From all the research I’ve seen, this prop should be a dynamite match for the boat motor combo. And I should be able to get full RPM from it.

The motor is mounted all the way down on the transom, and I’ve been told a number of times to raise it one hole. Being this is a blind hole mounted motor, I’m hesitant to drill another set of holes in the transom ¾ inch from the original holes. I’m not looking to go with a jack plate either.

I can get full motor RPM with the aluminum prop as the motor is currently mounted, but not with the stainless one. It would seem that I should be able to do so.

I’m a little stumped here.

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4,800 is not a good number.

Is your new prop Stainless Steel? It sounds like it is...

If so, even though you've reduced the pitch by 2", the loss of 500 rpm's is most likely do to the fact that most stainless props are "cupped" towards the trailing edge of each blade. The cup allows the prop to get a better "bite" on the water by holding the water on the face of the blade longer. It also makes your engine work a bit harder.

Believe in your tach, it has not magically readjusted itself. If you don't want to or can't adjust the height of your engine, you may need to either reduce the diameter or reduce the pitch another two inches to get those revs back where they belong.

Keep us posted,

Norm

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Got out to the delta gain today finally and ran the boat again with me and a buddy.

25 gallons of fuel, kicker motor 3 gallons in the kicker tanks, two guys, ice chest and gear.

Top RPM at WOT, indicated 5200/5300.
Speed (GPS), 38.3 MPH.



I am of the impression that the tach is correct and that is about all I'm going to get out of this setup without raising the motor. (Currently on the bottom hole right on the transom).

I did not swap the old prop back on, I think this is giving me accurate numbers.

Now I really have no excuse to drilling some holes.

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OK, 5200-5300 RPM heavily loaded, is more like it. Nice.

Yes, if that motor is all the way down, raise it two sets of bolts holes. I think you will be surprised at the difference in how the boats feels after that adjustment

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I like the specs of the older prop. More RPM's and more top end speed.

What brand is the 15 pitch turbo prop?

I had 2 OMC/BRP aluminum props for my prior Montauk with a Evinrude 70 hp
1. 13.75 x 15 part# 391198
2. 13.25 x 17 part# 391199
The 15 pitch had a better hole shot but the 17 pitch was a couple mph faster at top end.
The 15 pitch also had a few more rpm's at wot. You seem to have less.

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A bit of history may be in order..

The original BRP prop is a 13.25 x 17 3 blade, p/n 763463.
The turbo prop is a 13.25 x 15 3 blade, p/n DT-13215-R Originally I was going to go with a stiletto prop in that sizing; it was out of stock and this is the one subbed in at no additional cost. (thanks again Tom C.)
The prop I had on this motor when I bought it was a OMC 13.75 x 15, p/n 391198. It did the same as you are relating in your experience; better holeshot, higher RPM,. lower top speed. I did a lot of research and based on input from this site and CW, found I was underpropped. Consensus at the time was to go with a 13.25 x 17 pprop, in SS or Alum. I went cheapo and bought aluminum.
Got the money up to go stainless, and based again on input from here and CW, went with a stiletto 13.25 x 15 due to the performance of this prop being very much like a 17 pitch prop.

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That helps...

However, you are only under propped if you exceed redline of 5500 RPM (I believe that is redline for that engine)...

It still seems to me that the 13.25 x 17 prop gave you the perfect WOT RPM of 5300 to 5500 and gave you a good top end speed of 39.1 mph.....
Like you said, this #391198 15 pitch prop also gave you a good hole shot....

No harm in trying other props but I think you had a good one matched for your boat.
Of course if you experiment with raising the engine, then trying other props might help change the equation....

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Joe, the 39.1 at 5300-5500 came with the 13.25 x 17 aluminum, not the 13.75 x 15. The 15 pitch prop ran WOT at 5500-5700 easily with about 33-34 MPH top speed.

The 17 pitch aluminum prop did very well, at lower speeds, but at WOT felt like it was slipping in turns and not biting like I would expect. My buddies are telling my I'm nuts worrying about the prop/motor setup so much; I know they are probably right, but being kinda OCD, I'll never stop thinking about it unitl I get the setup as good as I can get it. That meant stainless for the prop, and now it means raising the motor.

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Yep.... My mistake...

I meant the 17 pitch that you had on their originally....

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Joe -- The brand of propeller that Larry has is TURBO.

http://www.turbo-props.com/

The TURBO brand is the sibling brand to STILETTO. Both are made by Precision Propeller Industries, Inc. which was bought by Yamaha last year. PPI had been making many of Yamaha's propellers for some time, as well as props for other manufacturers.

The TURBO brand is the premium brand while Stiletto is the more economical brand. However, in the case of the TURBO Turbo 1 model and the Stiletto Advantage model, they are the same casting, different decals.

Comparing propeller pitch between different models of propeller can be confusing because they do not all perform the same due to their different designs.

In this case we see the 15" pitch Turbo performs like it has more pitch than the 17" BRP aluminum prop.

It should also be noted that comparing performance on different days under different conditions (i.e. heavily loaded) will yield different results. Larry had previously reported the 15" Turbo yielded 39.7 mph GPS speed. Once he gets his motor raised he will be well over 40 MPH. well beyond the potential of his aluminum prop.