Any 90 Yamaha 2s performance tips?

[Spdloader]

Hi all,
I'd like to take this opportunity to say HI! to the group. I'm a newbie to the owners group, but not to boating. I even manned the Harbor Patrol/SCUBA Dive and Recovery boat in Carolina Beach, NC in 1991 and '92 as an officer there. I've been involved with boats in one way or another since about 1973, when my dad bought our first 16ft Sportcraft, with a Chrysler 85.


There have been a lot of boats and such since then, but currently I own an '05 Triumph 190Bay with the Yamaha 90 2Stroke. Easily the best boat I've ever owned, but I'd like to get the most out of my motor.

Are there any tips or tricks with this specific motor I can perform? It runs fine and is reliable, just doesn't quite give the power I'd like. I can't afford to swap up to the 150, so I'd like to get as much as possible out of this one.

Thanks in advance!

Spdloader
C. Tracy Bryson
Little River, SC.

 

[fridaysoff]

Tracey,
Welcome aboard. I ran one of the "Winner" cruise boats in Carolina Bch. about the time you were there and lived there from 1978 to 1995. I'm sure I've seen you. You may want to do a search on this site for Bob's machine shop stabilizer plate. I put one on my 170CC Triumph that I had and loved the results. It helped the boat to plane faster and I could run on plane at a lower speed in a chop. It is solid and does not look like the "whaletail" looking doelfins. Check it out and good luck.
John D.

 

[jebsr50]

Spdloader: I can't help you with the yamaha but would like to say welcome. I know you will enjoy the Triumph and this site. Great for good information and just good people. James

 

[Spdloader]

Winner boats! Wow those were the days huh? Remember all the drunks fighting in the street between the Winner docks and the Police Department? I sure do, still have the scars! lol

 

[fridaysoff]

Tracey,
Thats why I am pretty sure I met you back then. We were always calling you guys to come over to the boats to help us with the rowdy ones. Thanks for all of the help.Enjoy that Triumph!
John D.

 

[BigBird]

90 also

Welcome Tracy,
I bought my 2002 190 bay in april. It alos has a Yam 90 2stroke. i am planning getting a ss prop and bms plate.
I also have been looking into a set of boysens but dont want to sacrifice the reliability that i have now.
BTW-I love to go get scallops from Ellas when I am over your way!
Give me a shout anytime if you want to network on the 190s.
Lindsay

 

[BarryB]

More power

Hi CTB,

1. Anything you add to the lower unit that touches the water increases drag. Drag slows the boat.
2. What prop do you run?
3. What is the RPM at wide open throttle?
4. What speed (using a GPS) does the boat run at WOT?

If the pitch on the prop doesn't allow for the maximum RPM for your motor, you will not produce the maximum HP.

Also, with the motor OFF, remove the cowling and cover to the carbs. Look at the butterflys with someone holding the throttle all the way forward. Are the butterflys horizontal? If not, then the carbs are not adjusted properly. This would show up with less than steller HP.

 

[Spdloader]

Hi CTB,

1. Anything you add to the lower unit that touches the water increases drag. Drag slows the boat.
2. What prop do you run?
3. What is the RPM at wide open throttle?
4. What speed (using a GPS) does the boat run at WOT?

If the pitch on the prop doesn't allow for the maximum RPM for your motor, you will not produce the maximum HP.

Also, with the motor OFF, remove the cowling and cover to the carbs. Look at the butterflys with someone holding the throttle all the way forward. Are the butterflys horizontal? If not, then the carbs are not adjusted properly. This would show up with less than steller HP.

I should start by saying I purchased this boat "almost new" it had only 4 hours on it, and my low rpm problem was present at the start, but I was unaware it was a problem until recently.

I am only at 4200 rpm at WOT, and barely 32mph GPS in very smooth water. If I trim it too high, I can get more rpms, but no more speed. I'm running the stock 13 3/4 x 17 K prop that came on it from the dealer. I intend to try both a 15 and a 13 pitch to see what runs best. The motor does have a hydrofoil, the huge whaletail type, the brand escapes me right now, and the boat has a big t-top on it. There are no water issues, or hidden water on or in the hull of the boat.
The hole shot is horrible, and it gets on plane slowly. I was told by a local marine dealer that my low rpm at WOT was lugging the engine, and I was probably going to damage it, and I should try a different prop. I'm not trying to make a race boat out of it, I'd just like it to perform the way it is supposed to, and stay reliable, and I'd like a little more power when traveling against the tide. Looks like maybe a new prop will solve a lot of that.

I also have an issue with it not idling well after warming up. It shakes badly and coughs then stalls, but will immediately restart. Makes it tough to load on the trailer in a crosswind with a strong current though.
I replaced the fuel pump on the dealers advice, but it didn't help. I have read here about removing the backflow valve from the fuel line, but haven't had the time to look for it, (I don't know where it is) I intend to perform that this weekend. I assume its under the floor near the center console where the tank is. Someone correct me if I'm wrong there, please!

 

[BarryB]

More help

Hi CTB,

Replacing parts is an expensive way of diagnosing a problem.

First check out the Yamaha web site:
Two Stroke Midrange Home

The RPM range for power is between 4500 and 5500. You're at 4200 which is too low and, as the dealer said, you are loading down the motor. If you change props from a 17 to a 15 inch pitch, you should gain about 400 RPMs. That would still put you at the low end. However a 13 inch pitch prop may work better for you. Hopefully, the dealer will have spare props you can test with.

It is possible that the motor sat for a long time with some fuel in the float bowl. That fuel may have become gummy and clogged up the main jet a bit. The reason I say this is because you stated the boat will not idle too well. The idle circuit may be clogged too. At closed throttle, the fuel passes through the idle circuit and then as the throttle opens up, fuel begins to flow through the main jet.
The Yamaha service manual is available through Yamaha. I ordered one online, however, you may be able to get one through other book sellers and save a few dollars.

Depending on the year of make (mine was produced 8/06) the catalog number for the 90TLR motor is:
LIT-18616-02-66

The manual covers everything on the motor including rebuilding the carburetors and throttle adjustment. Even if you don't do the work yourself, a little bit of knowledge will help.

If you think you have a fuel, fuel line, or filter problem, borrow a 6 gallon tank and attach directly to the motor using the supplied line from the spare tank. Try out that system. If there is no change, then you don't have a problem before the motor.

Also, check out the Yamaha performance bulletins. They can help. Here is one similar to mine:

http://www.yamaha-motor.com/assets/...tb_2StrokePerf_HPMidPort_70hp_01213-TPH-Z.pdf