Boyesen Reeds for a 90hp Yamaha- Good idea?

[Bazooka Joe]

I have an almost new 2004 90hp Yam and am looking to boost the low end power. It's presently badly lacking in holeshot power for pulling waterskiers. The engine just doesn't pull strongly until 4000 rpm, but runs nicely after that.

Previously, I had a 88hp Johnson on this same boat and the Yamaha does not come close in holeshot performance. The Yam is a MUCH nicer running motor, though.

Current setup, for reference:
17p Ballistic SS, w/ three .38" dia ventilation holes.
16ft Aluminum Smokercraft (approx hull weight = 875#)
Full throttle rpm = 5900 w/ one person, 5600 w/ two people.
The idle jets have been adjusted to 1.5 turns out each. (stock was 1.75 for the bottom two cyls, and .75 for the top cyl)

So, what I am wondering- Does anyone have experience w/ Boyesen reeds on this particular motor? The Boyesen reeds generally worked well on every dirtbike I have ever installed them in, so I am thinking that they would be a good modification for this motor.

I also have a 16p (Merc) SS Rapture which I am going to try as soon as I get a new thrust washer and modify it to adapt to the prop's Merc hub.

Thanks in advance for quality answers and suggestions.

BZ Joe

[tripleb]

Hey Bazooka Joe,

I can't answer your Boyesen reeds question but have some interesting observations to pass along to you.

I have:
17ft. Key West CC
750lbs. Dry Hull Weight (Approx.)
2005 Yamaha 90 TLRD
13.25 x 17 Stiletto SS Prop

Mine hops out of the hole like it was shot out of a cannon. I do not achieve the RPM level that you do ..... sounds as if you are actually "over revving" the engine somewhat. I believe the motor has a high end range of 4500 - 5500 rpms.

[Bazooka Joe]

TripleB,

Thanks for the info on your rig. That is interesting that you have excellent holeshot but don't pull so many revs on top end. Mine is opposite- I can pull (or overpull) the top speed of the 17P but suffer on take off (that is why I added ventilation holes which help a bit). Tomorrow, I'll call to a semi-local prop shop and see what they think I should do next. I've worked with them before and they seem to know a whole bunch of tricks to wake up a prop. I had them work on my previous Johnson's Michigan prop and they did some excellent work.

Also, I did get the thrust washer so I should be able to give the 16p a spin soon.

My outboard seems to pull and pull on the upper revs and doesn't seem to fall off the power until past 6000. I read a test in Bass & Walleye boats on the 90hp outboards. They said the Yam pulled peak hp at 6000, which is interesting b/c like you said, Yam rates it to run 45-5500.

Couple of Qs about your boat. When you slap the throttle wide open from a dead start, what rpm does the motor run while planing out? Mine will hang in the low 3K, until it gets to upper 3K and then it rips into low 4K and then pulls fine. Also, do you know your top gps speed is? I'm running mid 43mph on GPS.

Thanks again for the reply.

[tripleb]

Hey Bazooka Joe,

Right at 3K to plane. Actually the boat is real "happy" at 3K ..... 25 mph, nice ride.

Top GPS speed ..... I have seen 47 mph at 4600 rpm.

[jb123]

myself, i wouldnt change yamahas superior engineering to aftermarket parts, it would probably void any warranty if you have one. for the performance i would play with props and motor elevation,whether mount changes or jack plate. and high rpm`s are great but keep in mind they will reduce your motor life and put much strain on the wristpins.

[Bazooka Joe]

TripleB,
Your performance certainly sounds good, 47mph with a 90hp is nothing to scoff at. I'd be GRINNING if I could get that from mine. 46.5 mph was the best the 90 Johnson could pull.

However, something doesn't sound quite correct with your tach readings. With a 17p prop, it is not possible to achieve those speeds at those rpms. Could it be possible that you have your tach set at the 8 pole setting? If so, then the actual rpms would be 1.25X and the the speed/rpm numbers would be completely in the expected ballpark. Adjusting for such a setting, your plane out would be 4000k and the top rpm would be 6134 rpm.

Just supposing that to be the case, my 90 Yam certainly does come alive in a big way at 4000 rpm, and I will be trying to get my prop tuned for holeshot at that rpm. Thanks again for the feedback.


JB123,
I would not consider Yamaha's engineering to be so far superior that aftermarket parts are of no value. Yamaha = good stuff, but improvements can be made. As to the warranty... Warranty, schmaranty. I have two Yamaha 2003 YZ250F motocrossers that my son & I race. The potential repair costs on those bikes are easily more than a whole powerhead for this 90 outboard, yet we trash the bikes on a regular basis. Besides, the addition of aftermarket parts will only void warranty if the dealer is a **** and if the aftermarket part causes the damage. In the worst case, I tear it down and fix it myself. No biggee, I'm a big kid and known to take risks.

[tripleb]

Hey Bazooka Joe,

Well, don't know what to tell you ..... after reading your suggestion, I took out my tach out to verify switch setting ..... it is set for the proper 12 pole alternator position as per Teleflex's instructions.

My 90TLRD replaces a 70hp Evinrude. Top speed with the 70 was about 40 (on a good day). This 90 is brand new, just over a week old ..... still running the double oil for break in period. I have about 6 hours on it

Keep in mind that those speeds are not pulling a water skier. It is just me and the boat, with a little bit of fishing gear.

[Bazooka Joe]

TripleB,
My bad on the "8 pole" statement. I was thinking 6 pole was correct. I checked my tach- 12 pole just like yours. I dunno what to think either. Unless, connecting to the J/E terminal could cause reading errors?

But back at the speed/rpm/gps/theorectical numbers... The Yam 90 has a rev limiter at 6200 rpm. Here's what I figured-
6200 rpm / 2:00 lower unit ratio = 3100 prop rpm
3100 rpm x 17" pitch = 52,700" = 4392 ft
4392/5280 = .832 mile
.832 x 60 = 49.9 mph max possible.
49.9 minus 10% slippage = 44.9 mph

SS props with extra cupping and/or higher actual pitch can result in higher speed numbers.

Does the outboard sound like it's really howling? Keep in mind that the 3 cyls aren't going to be screamers like a 4 cyl.

[tripleb]

Hey Bazooka Joe,

Good job, I was never great at math

No, the motor does not sound as if it is "howling". It sounds as if it could use another 600 - 800 rpms. My old 70 would max out at about 6000 rpm (WOT) and sounded as if it were going to come apart. You could actually hear the carburetors "sucking" every bit of gas the VRO system could pump.

What is tough to factor into the calculations are boat hull drag and water conditions, both of which will affect the final calculated numbers.

My Keywest CC has a smooth bottom with about 12 degrees of deadrise. The cavitation plate is about 3/4" above the bottom of the boat.

[Bazooka Joe]

TripleB,
Over at the Yamaha site, I found some performance test bulletins, where they rigged up sample boats w/ various Yam motors. The bulk of the Yam 90s were turning low 40ish mph, so your (and my) speed is certainly near the top of the pile. I would point out that they were running 19+ pitch props to get much over 40 mph and that they always propped to hit 5500 rpm.

This would indicate to me that either your prop is mis-marked (maybe, but probably not), or your GPS has bad readings (doubtful, unless you have it set to Km/hr. ), or the tach is giving bad readings. I'd still look at that tach.

Myself, I'd bet that your engine is turning some big revs but just doesn't sound like it. Remember that the Yam 90 is a smoooooth running outboard and doesn't put on such stressful sounding antics as the OMCs. My 90 OMC howled like an airplane at 5800rpm & full trim.

Reeds update.... I'm going for the Boyesen reeds. I talked to Boyesen tech department today. The guy said the reeds will do a whole bunch of good for the Yam 90's lower end power, but not to really expect much on top end power. A place called Bob's MachineShop has the reeds for $70 and it only needs a couple of $3 gaskets. It looks like a fairly easy install. Stay tuned for a report in a couple of weeks.

[tripleb]

Hey Bazooka Joe,

Well, the tach is old, probably about 10 years. I will have the Dealer check it out during the 20 hour "check up".

Good luck with your reed install.

[dtmackey]

I would not waste your time with fiberglass reeds. BTW - Boyseen reeds are way overpriced.

I'm sure they have all these slick dyno graphs (compliments of the marketing folks) that show increases in power and claims from owners, but the truth is you would not feel anything. The story may be different if you were running a hydro and the engine was ported, head milled, jetted and turning about 9000rpm. This is just my experience with 2 stroke motors after playing with them for 20 years. I'm sure someone with a marketing degree could tell you that your engine will breath fire, but these could be the same people telling you that with a little gismo your pickup truck could get 80mpg.

I think you get the picture.

[Bazooka Joe]

DTMackey,

Thanks for your input.

I'm really surprised to hear that fiberglass reeds are bad news. Are you speaking as a general term or do you have experience with installing them in boat motors, specifically in a Yam 90?

What material are the stock reeds and what would be the preferable material? I am not sure what material the Yam Boyesen reeds will be; Boyesen makes motorcycle reeds in both fiberglass and carbon fiber. The fiberglass are typically better low end response and the CF are better durability. I'm expecting that the Boyesen outboard reeds will be carbon fiber material to increase life expectancy. The selection of caliper thickness will be the main factor in response charatoristics with whatever material is used.

Costwise, the Yam reeds are about the same. I see that Boats.net has the replacement OEM reeds at $25ish per cyl = $75 for the set. A set of Boyesens are $85 retail, $70 discount pricing. Granted, my stock reeds are almost brand new and I do NOT need to replace the stock reeds at this time. I am doing this strictly for a low end power boost.

Wait for the report. I'll either be wearing egg on my face or I'll be hoisting a brew.

Have a great 4th!

[dtmackey]

Baz - I have not installed them in a Yamaha 90, but have installed them in other motors with no difference, including a Johnson 110hp V4. The Yamaha lacks one thing and that is displacement. Adding all these simple bolt ons is no substitute for displacement. If you are looking for HP gains, reeds would be one of the last things I would look at. Try porting, milling the head, bumping the timing (run good fuel), or just buy a bigger motor. My rule of thumb is to power the boat with 10% more power than rated and I never have an issue. Since I am not a full thottle nut the motor also has a much easier life since it's not really working close to it's rate power.

just my $0.02

D-

[Bazooka Joe]

DTM,

The reeds are in. I was very impressed with Yamaha's detail to construction and choice of materials. The reed plate gasket is made of VERY good material and retails for only $3ish. All of the fasteners are good stuff and the engine is basically easy to work on. SO much better construction than my previous fat V-4 90hp OMC.

I got it out for a test spin. The Boyesen reed verdict.... drum roll plz.... The Boyesen reeds are definitely an improvement over the stock stainless reeds.

Idle speed is smoother (idles down to 1.8 mph on the locator), mid range is quiet, and top end is somewhat higher on the tach. I didn't have the GPS with to verify top speeds. Going off the tach, it's about a mph or so. Holeshot is better, although I didn't try waterskiing to give it the true acid test for holeshot. The boat could probably benefit from a hydrofoil. (the motor is mounted high enough that the h-foil will be out of the water at speed).

Bottom line, I feel that the Boyesen reeds are/were worth the $$ and would reccommend them for this specific outboard.