Yamaha 150 RPM's

[Gremlin]

Got a '99 Saltwater Series 150 on 20' Key West. Runs great, but top end RPM's is around 3800, speed 32mph with 3 adults. Everything I've seen is that RPM's should get up to 5000-5500. Any suggestions on where to start?
Again it runs great, but would like to see if I could increase top end speed.

 

[v12mac]

Re: Yamaha 150 RPM's

150 HP on a 20' key west should FLY. Somewhere around 45-50 mph
Something is not right.

 

[Casco Bay Outrage]

Re: Yamaha 150 RPM's

How long have you owned the boat?

Was speed measured off of GPS or gauges?

What speed/rpm's does the boat do when are alone?

What make, model and size is the propeller. You may need to take it off to get the size.

 

[rodbolt]

Re: Yamaha 150 RPM's

post the full model number as there were several variants of the 150 in 1999 that used different fuel and ign systems?

 

[Gremlin]

Re: Yamaha 150 RPM's

Key West reccomends a 14 1/4 diam., 17 pitch for this boat. I am attempting to remove prop to see what is currently on the boat, but previous owner installed McGard propeller lock. Anyone familiar on how to get these off.

 

[Casco Bay Outrage]

Re: Yamaha 150 RPM's

Have you seen this?

http://www.mcgard.com/Home/MarineProducts/PropellerLocks

Give the company a call if you don't have the special removal socket.

 

[Gremlin]

Re: Yamaha 150 RPM's

Got the prop off, its a 14" diameter, with 19 pitch. Key West recommends 14 1/4" diameter, with 17 pitch.
Do you think its worth swapping, should I notice an increase in RPM's?

 

[Captain Paul]

Re: Yamaha 150 RPM's

As RodBolt suggested, you should supply model # to be sure, but to me you are not spinning enough RPM's. The book for my V-MAx 150 says 4500-5500 is top RPM range. Moving to the 17 pitch prop will give you about 400 more RPM. Are you trimmed out all the way when trying to get max RPM's?

 

[Gremlin]

Re: Yamaha 150 RPM's

I will get motor info. you requested.
When you say trimmed out all the way, do you mean raising the trim of the motor up? I don't always do that, I've messed around with it some, how high should you raise the motor?

Thanks

 

[Captain Paul]

Re: Yamaha 150 RPM's

Yes, raising the motor up. It will increase your RPM's. If the prop sucks air, you are trimmed too high. You will hear a noticble change in engine sound if the prop can't bite the water. This is not a scientific explanation, but think of it this way. When you trim the motor up, you put down pressure on the back of your boat, in turn, lifting the front of the boat out of the water. You are also raising the prop to the surface, meaning less lower unit in the water. Usually, the less boat in the water, the faster it goes. You do not want the motor trimmed up when you are first starting out. Once you are under way, trim it up. You need to get the feel for it in different conditions. BE CAREFUL!. When you are trimmed up high, the boat does not handle the same. While at speed, you need to trim down to navigate a turn or a wave.

 

[ghuru45]

Re: Yamaha 150 RPM's

i just posted the same problem with my 2005 yamaha 150 4stroke.. I posted under prop issues.. If any of you guys figure out anything please reply to my post with any help... thanks a ton

 

[Gremlin]

Re: Yamaha 150 RPM's

Ok, got the Hustler 14 1/4 17p blade on this morning and took it to the lake. Had appx. 20 gallons of fuel, myself and my son, appx. 340 lbs. of people, and no other equipment. Noticed immediately from takeoff the difference in acceleration. Previously the motor would lug around 25k rpm's, then sloooowly move up to a peak of 34-36k rpm's depending on load. Now in about 2-3 seconds its doing 35k rpm's, peaked at 45k rpm's and a speed of 36mph measured off of gps. It got to plane so much quicker than before, previously it sometimes would never get to plane, and just squat in the water. The motor just sounded better than before too, it seemed to have that peak rpm that was missing before. It previously just sounded like it was working so hard to get to speed, but couldn't make it.
Yamaha has WOT at between 45-55k rpm's, so not quite there, but a huge improvement from before. I think I may change all the plugs, see if I notice any difference there, but am extremley happy with the results.
Thanks to all that responded and gave me ideas to fix the problem. I know some of you had wanted model number, and I keep forgetting to get that, boat's stored at my parents house.
Any other comments or suggestions are welcome.
I heard so many positive comments about the Hustler and I'm a believer. Spent $100 and change for the prop and what a difference. Am going to sell my stainless now, probably recoup what I spent on the Hustler.
Thanks again for all the advice from everyone, it feels so good being able to work on the boat myself and not having to take it to the shop for every little thing.

 

[Casco Bay Outrage]

Re: Yamaha 150 RPM's

While that is an improvement, I think the propeller/motor height still not right.

With a light load, and by yourself WOT should be 53-5500 RPM's.

Can you tell us what holes in the top set are used to bolt the engine to the transom. Count down from the top of the transom. The bolts are in the X st/rd hole.

With the engine trimmed out vertical, where is the anti-cavitation plate, height wise compared to the bottom of the keel? Use a long straight edge measure with a tape the distance above or below the straight edge.

When at a medium cruise, trimmed out, the ant-cavitation plate should be at or slightly out of the water.

 

[Gremlin]

Re: Yamaha 150 RPM's

I decided to pull the plugs on the motor, all had signs of normal wear except one. It looked like it was brand new out of the box. I'm thinking its not firing, and suggestions where to start.

Thanks

 

[cousinabe]

Re: Yamaha 150 RPM's

get the model number off the bracket on the port side and post it.
no sense guessing at what model you have as they are all different.

and what cylinder# is not firing?

 

[Gremlin]

Re: Yamaha 150 RPM's

I don't know the proper term, but as your facing the rear of the motor, the bottom right plug is the one that shows no carbon, and looks like it hasn't been firing.
Model number is S150TXRX.

Thanks

 

[v12mac]

Re: Yamaha 150 RPM's

Gremlin,
It might sting a bit but here goes, Take your boat to a good mechanic. You have already thrown money at a prop that you might not have needed to buy. Pay for his knowledge and troubleshooting skills, build experience, and enjoy your boat.

 

[Gremlin]

Re: Yamaha 150 RPM's

V12 Mac, took your advice and dropped the boat off at a certified Yamaha dealer today. Hopefully it won't be too bad, and will be ready for the start of scallop season.

 

[v12mac]

Re: Yamaha 150 RPM's

Cool, when you pick it back up ask lots of questions look at everything. Learn all you can without being too much of a pest. Once it is running 100% you will be ready to tinker with the small stuff and work up to the bigger stuff. More importantly you will be out boating!

 

[Gremlin]

Re: Yamaha 150 RPM's

Good advice V12 Mac. When I was dropping it off and describing the problem with RPM's, the mechanic said it sounded like the carbs needed to be cleaned. Is that difficult to do on your own? I have owners manual, but have never tackled something like that. Reading a lot of other posts it sounds like with the ethanol in the gas, it may be something that needs to be before every boating season.

Thanks.