Need Yamaha F90 Performance Feedback

[Secret Spot]

After recovering from a car accident and installing Lenco Trim Tabs, I finally got the Secret Spot out to break in the new Yamaha F90.  The dealer recommended a 13.25X17 prop.  After doing the whole 1st and 2nd hour thing during break in, I opened the engine up to full throttle.  At WOT I was able to get 5500 RPM and 31 MPH.  The Secret Spot is a 1991 17' Sea Ranger.  I was topped off with fuel & water and had another 500 lbs between my buddy and I.  Does   know if the RPM and speed I obtained is where it should be?  I was extremely happy with the power and hole shot performance.  The trim tabs definitely make a huge impact with dropping the bow and getting on plane.  Another thing that blew me away was when I first started it, I didn't hear it running!

Larry - Secret Spot

 

[croaker stroker]

Sounds like you got it dialed in perfect. Thumbs up to Mauer Marine.

[Secret Spot]

Thanks Mark...  While the operators manual stated that the optimal RPM at WOT should be between 5000-6000, it didn't say anything about speed as I am sure it varies from boat to boat.  In any event, I don't see myself running at WOT.  I typically run in the ocean anywhere from 15-22 mph depending on sea conditions.  Not having any idea as to expected speed and economy, I wanted to make sure I was in the ball park.  Thanks again...

Larry - Secret Spot

[Danno]

You could squeeze another couple hundred RPM's out of here by dropping down to a 15" prop but you'd be going the same speed with higher RPM and that just adds noise to your drive. If you had rivers to deal with or bars to cross, I might be stronger on the change because you would have better bite out of the hole but since you boating zone is relatively easy, you're in great shape with the 17".

[Threeweight]

Sounds about right. 

My Suzuki 90 is running a 14 by 17, but it is geared a bit lower than the Yamaha.  My 17 Chaser is also a little bit lighter than your boat, and my typical passenger load is a little lighter.  On the river, I hit somewhere between 32-34 mph, according to the GPS, at 5900 RPM.  The newer Suzi 90's like to rev (I think the suggested RPM range on it is 5300-6300.)

[Enniberg]

This thread is of great interest to me too.

Enniberg was recently repowered with a 2006 Yamaha F90, and yesterday Ron (Fish On) and I too it out for a shake down cruise.

Love the motor - runs very smooth and seems to be sipping fuel. :party:

The motor came with a new 13X19 prop, which probably was ideal for the 16 ft Whaler that it was mounted to before. I did not expect much from this prop on a 17 Chaser, but it turned out to work quite well.

we briefly opened it up and the highest speed I saw on the gps was 33.6 mph @ 5600 rpm. It cruised nicely in the mid twenties at 4400 rpm. Hole shot is the downside - it struggles a bit to get planing, but this will probably be alleviated (at least partially) by installing trim tabs.

The boat was loaded with 2 guys, around 18 gallons of fuel, kicker, 2 batteries, and quite a bit of fishing gear and other stuff.

I think I will still go to a 17 pitch to get better hole shot and more control in the big swells offshore, but the 19 is certainly not bad.

We determined that the motor still sits a little lower than what would be considered ideal, but judging by the performance numbers, it does not suffer too badly.

Johan

[croaker stroker]

Yamaha has a pretty good resource for choosing a prop.  You just choose which motor you have, then pick a boat close to the size and shape of the Arima. Then you will see performance details including RPM, Speed, prop size, Etc.

http://www.yamaha-motor.com/outboard/products/perfbull.aspx

Here's the owners manual (notice that you don't run the engine while hooked to the garden hose fitting at the top of the motor, pg. 58)

http://www.yamaha-motor.com/assets/service/manuals/1/LIT-18626-07-12_1406.pdf

[Enniberg]

I not sure what would be the perfect size prop for my application.

Looking at what Larry is getting with a 13.25x17 on Secret Spot, he has good hole shot and top speed is pretty good too, but I have been told that it is best if rpm at WOT is close to the top end of the range, which is 6000 rpm for this motor, and if so, his WOT rpm of 5500 could be slightly improved on.

With the 13x19 on Enniberg, I am getting 5600 rpm at WOT and great speed, but hole shot could be better.

I would like to retain a top speed in the 30 mph range, while significantly improving hole shot and getting another couple of hundred rpm at WOT, but it just seems to be that I will have to sacrifice on something to achieve the other. Suggestions

Johan

[CanvasGuy]

Dare I say.....

get trim tabs..or at least smart tabs..

the point being that hole shot improvement.. not to metion stabilty control..with those big BUTTS sliding around the floor while your heading in..

I just ordered a set of Lenco

electrics 9X12 and the best switch..retract led..for just under 600.00
shipping 9.00 and no tax..discount marine..

I use a 4 blade prop with my honda 90 with 6200 WOT  but with a lot of equiptment and three fishermen..you need help up on the step..
just my :twocents:

[Threeweight]

Johan is a Smart Tabs believer... he may already have em' on the boat!

My suggestions ...

If you want torque and faster planing speed w/ a load, look at a 4 blade Solas prop, in the 13 1/4 by 15 size.  I have one I used on my Suzuki that is 13 3/4 x 15, and it turns right at 6200 RPM (max on my motor is 6300).  My motor is geared lower than yours, so you should be able to a little lower on the RPM's than mine.  They are pretty cheap, and also help give you a little more aggressive bite for higher speed steering.  Downside is you will lose some fuel economy (as well as top speed).

You could also think about taking your existing prop into a shop and having them re-pitch it down to 16 or 15.

[Enniberg]

Thanks for the input Gary, I just talked to a Solas dealer who recommended me to go to a 4 blade. Worth considering.

It seems that torque is not Yamaha's strong point.

I bought a set of Smart Tabs a few weeks ago (55 bucks, Cabela's bargain cave  :biggrin:) - just need to install them.

[croaker stroker]

I agree with 3WT on the four blade. In our fishing area we go out in 3' to 4' West swell. On the way back it is difficult to "stay on plane" with any boat.  The four blade prop sure helps cure that problem.

Trim tabs do help to get up and stay on plane, but if you are adjusting them "nose down" to stay on plane, watch out when you dig into the next swell. The four blade gives you a low gear to power through while still keeping the nose up.

[Enniberg]

Steve, how did you know I am a Smart Tabs believer?? :biggrin:

I ditched hydraulics for Smart Tabs on my previous Arima's, and never looked back - freedom from fiddling with switches

Considering the current gas prices (~ $5.20 per US Gallon at the pumps where I live), giving up on fuel economy, even if it is just a little bit - sucks! But I realize that propping a boat will always be a compromise, and in the end I have to prioritize my criteria.

[Threeweight]

Your experiences with Smartabs on the original Enniberg were one of the contributing factors to my installing them on the Lady J.

I'm running a 14x17 3 blade now, which is probably about the best compromise between torque and speed/fuel economy on my motor and boat, but if I were running offshore a lot and needing to be able to quickly jump on and off plane, I'd probably go back to my 4 blade. 

If I ever get the engine monitor cable for my Suzuki so I can display real-time fuel flow, I can give a better analysis of how the two props affect fuel economy.

[fishorcrab]

I have a SC16 with the F90 Yamaha.  It came with a 17 pitch prop and while it had a great hole shot, it left something to be desired at higher speeds.  I did like the fact that it would troll about 1.5 mph. 

I switched to a 19 pitch and have been very happy with it.  Hole shot went from about 4.5 sec to 6 sec or so but the main advantage was that 4000 rpm became a very nice cruising sweet spot. It was on plane and very economical to run.  Trolling speed went to about 2.5 mph and docking took some time to relearn at the higher speed.  In and out of gear for docking became the norm. 

Both batteries are located in the cuddy and the 6hp kicker weighs about 60 lbs.  No trim tabs on the boat so I can't say what difference they might make.

The main thing is that it isn't just about WOT.  It has been a couple of years and I don't have speed vs. rpm at WOT handy between the two props but both were within the range.  Both props are 3 blade aluminum.  Borrow a 17 if you can and see what difference it makes. 

Another possibility is to see if your prop could be repitched a little shorter.

Paul

[Secret Spot]

I got the Secret Spot out today and I was able to get the RPMs up to 5700 and 33 MPH by trimming the F90 up a little bit.  I played around with a little more, however, I couldn't top it.

Larry - Secret Spot

[croaker stroker]

I think that's pretty good. How's the idle ?

[Secret Spot]

Just purrrrrrrrrrrrrs.....  It's amazing how slow I can troll.  Will be perfect for halibut up in the Conception area.  I can see myself using the boat a heck of a lot more now that I have the 4 stroke.  I'm also loving it in a following sea.  The two stroke would want to bog and slow on the back side of a swell--the F90 appears to just chug right through it all without losing RPM.

Larry - Secret Spot

[croaker stroker]

Yes, and at 20mph, you can actually have a conversation.

I have hit the starter a couple of times while the motor was running.

[fishing eagle]

Isn't that a terrible sound & feeling when you do that Croaker?

[croaker stroker]

Isn't that a terrible sound & feeling when you do that Croaker?

Or trying to back the boat off the trailer. Wondering why it wont go. Only to realize you haven't undone the rear tiedowns.