Yammi 150hpdi - Only 5200rpms

[eyepatrol]

A couple of you have seen my rig, but in short, the prop would "blow out" or cavitate or whatever you want to call it, so I took it to a dealer and they lowered the motor to its lowest setting. I don't recall what RMPs I got before that, but right now I'm hitting 5200 which seems low, and that's with the motor fully trimmed out and a light load.

I've got a 14.25x19 Hustler prop and I'm wondering if it's the prop that is the problem or something else? I'm getting 45 - 46mph GPS and it seems to me the rig should be performing better (not only speed wise, but the blowing out too).

Any suggestions?

Oh yeah, the Yammi sits on an '04 Alumacraft Tourney Sport 175.

Thanks!

[PerchJerker]

Raising the motor will raise rpms, lowering it will drop your rpms. You know my boat and motor ...... I have my motor in the lowest hole / highest position.

Did they move it only 1 hole, or did they move it all the way to the bottom? If they moved it more than 1 hole I would try moving it in increments of 1 hole at a time to try to get your rpms back but not blow out.

Hustler prop is aluminum, right? With a 150 I think you should be running a stainless, maybe the Yam Pro (I think it only goes down to 21 pitch) or some other prop that you can get in 19 pitch.

Also, more blades on the prop should help your cornering and cavitation and handling a load, although you will give up a little speed on the top end. I say should help, because you never know for sure until you try.

Good luck getting it worked out.

[BoxMN]

Is your transome a 25" or 20"? I am familiar with 20" but not with 25". But that motor really should have a SS prop on it. Otherwise you are throwing away performance, really. Now, some will say SS will not break if you hit a rock and ruin your motor. Could happen, but not likely. We have run SS since '87 and never ruined a lower unit.

On our 20" transome with 150efi we are in middle hole. Raising up has helped. The blow out is because of the prop, not the hole, IMHO. Try a different prop, if the hustler is SS then try a different style design. I think you can get a Merc Tempest prop to fit that motor and that is what I would recommend. We use Tempest 19" on our TP175 and it works great. We tested a bunch, but long ago, as ours is a '97 and we did prop testing about 1999. Our motors should perform abouit the smae, and we get 49-50 mph gps with heavy load (three fat guys), and almost 52 with light load, and it never blows out unless we try to make it, and even then it is hard to do. Otherwise try a High Five prop, works AWESOME but reverse power is poor, which is why we don't use ours anymore, but it handles great.

Others with your exact rig will probably have better info for you. Good luck.

[marine_man]

I'm pretty sure he has a 20" transom. And I agree... moving the motor down to fix a blowout issue isn't the direction I would have gone - I would have explored a different prop first, per Perchjerker & BoxMN 's info above.

If you want to stay with the motor hole you're in you're going to need to drop to a 17 pitch to get your RPM's back up. That said, a 17 doesn't seem like a good fit for your rig Eric.

marine_man

[eyepatrol]

Wow!!! This is all GREAT information and I sure do appreciate it 100%!

First off, I'm going to say that I'll never take my rig to the boat dealer I've taken it to the last 2 times. First with the cavitation, they told me lowering the motor as low as it will go (which was only 1 more hole position) would solve the problem. I spent a couple hundred bucks and it obviously didn't solve a thing. Secondly, the leak I had under the console they told me was hydraulic steering fluid leak even though I told them there was no color, no smell, no greasy feeling to it, no taste even. I spent $210 on them to install a seal kit only to find that the leak was still there and upon my own inspection, I found it to be the speedo tube (?) was coming loose off the spedometer under the console. Pushed it back on and voila....no more leak. So $400+ down the tubes. Just as well taken 4 Hundos and thrown them in the fireplace.

Okay, there's my vent. Now on to answering your guys' questions.

Perchjerker

Yes, they lowered it 1 more hole which turns out is the lowest setting. Yes, the Hustler prop is an aluminum one. I'll have to look into a stainless prop in those pitches. I know stainless is quite spendy, so I'll probably have to live with the one I got for now. Probably keep it as a spare when I do get a stainless.

BoxMN

I guess I'm not sure if the transom is a 20" or 25", but I'm pretty certain the motor is the longer 25" shaft if that means anything (I'm not too mechanically inclined on boats and things). I hear what you're saying about SS props. I used to run the Hi-5 SS prop on my previous boat and it certainly performed much better with handling. There's always the risk of doing more damage w/ SS props, but I feel pretty confident driving on the lakes I fish. And yes, the 5-blade (Hi-5) prop doesn't reverse worth a darn!!!!

MM

I think I'd rather have the motor moved back up and then hopefully when I have the means to get a new prop, I can find a dealer that will let me test the Tempest props. Maybe try the 19" first and see how that performs before trying the 21". Who knows, maybe the 19" will do the trick and I won't have to test the 21".

Well I want to say thanks again for the replies. This gives me some good solid direction to follow/take. I just regret having to spend that kind of money on that dealer for things that just were not fixed or corrected. $410+ would have paid for a good portion of a new SS prop.

Oh, and one other thing....when the print on a prop says "14.25x19"......is the 14.25 the diameter and the 19 the pitch/twist? Or is it vice-versa? Or am I way off?

[PerchJerker]

14.25x19 = 14.25 diameter and 19 pitch, which theoretically means 1 revolution would move the prop forward 19 inches, but I say theoretically because slip comes into play.

I ran a Tempest for a while, loved it with a light load in the boat when I wanted to go fast, didn't really like it for overall performance though. But again, you never know until you try it on your boat.

I run a Rev 4 on my boat, very happy with that prop for overall performance. And as I said earlier, more blades should help with your handling and cavitation. I think you're looking at $550+ for that prop, not cheap.

Your best bet would be to test props, hopefully for free or for a small fee, to see what works best on your boat. Merc has the best selection of props and has hub kits to convert them to Yamaha motors, so they would work but a Yamaha prop might be simpler. If you can test props and find one that works on your rig, you might be able to find a used one for about half price, especially the 19 Tempest (seems like there's always some of them for sale).

If you really want to bring some variables into play, your motor could possibly be raised even higher than it was before. My opinion and experience is that most dealers mount the motors a little lower than they need to be, which robs a little performance out of them.

[croixflats]

I'm rather surprised to see a 19 pitch on a 150. I run a 21 pitch ss on my yamaha pro v 150 and I get a full 5600 rpm at 60 mph out of her with no cavatation at low range or high range.

With an aluminum prop you'd think you would want a stepper pitch in order to offset the flex in the aluminum.

Im not saying right, I'm not smart on things like that,Just letting you know what I run being we have simular moters

[BoxMN]

Croixflats, I'm just guessing, but you must have a glass bassboat for speeds like that with a 150, unless you are talking the speedo speed, not gps speed. He has alum hull in walleye styled boat, which like my boat is not a speed demon

However, I can get my boat to go "60" on the happy speedometer

[eyepatrol]

All very good information again. My main goal is to get rid of the cavitation and a close second is to improve the performance. With your guys' help, I've got some clear direction to take.

Thanks!

[croixflats]

Ya, it is a glass boat I didnt mention that figuring the aluminum boat would be lighter therefore perform better than glass. Buddy had 18ft alumicraft with opti 150 and it out performed me.

I thought a steeper pitch would get rid of the cavitation thinking the 150 might be to strong for a 19 pitch. Ofcourse steeper pitch would probly take some rpm's away to.

Hopefully eyepatrol you can get this figuered out. That cavitating can get irratatng, doesnt it?

[eyepatrol]

Yes it can, especially in the turns. Gotta play with the throttle and the trim at the same time whereas I'd rather just focus on the turn instead. Definitely have to take care of it before the kiddies get old enough to tube and start skiing.

[marine_man]

You will have to trim down some if you're going to make a harder turn - if you think about it, when you make a turn your motor raises out of the water some, losing some if the prop's bite in the water.

I don't suspect that's your problem Eric, but it is something worth noting.

marine_man

[eyepatrol]

Yep, that's definitely true. One thing about boats, you're not going to set any g-force records when turning.

[BoxMN]

Actually, with your TS175 and once you get the prop dialed in, you will be amazed at how it corners on a rail, no kidding. Especially when we were testing the Hi5 prop (which we bought and used for about 6 years before the Tempest) you simply canNOT get it to blow out even in WOT "turned to the stop" turns. If people were not careful and holding on, even the driver would go sliding off the seats Not to say that is desired, but with the right prop the boat will drive like its on a rail and not slide or blow out or even really "tilt" much.

Much different than our older 16' alumcraft semi-vee, not that one will skip-to-my-luuuuuu in a turn! ha!

[marine_man]

Especially when we were testing the Hi5 prop (which we bought and used for about 6 years before the Tempest)

I belive it corners nice with a Hi 5 - the extra blades make a big difference when it comes to holeshot and cornering.

marine_man

[setterguy]

What a great thread, I was going to post the exact same thing, about the exact same boat and motor. I am only getting 5000 rpm wot fully trimmed. I'm running a 13 3/4 x 21m. I am clueless as to what prop to try to get closer to 5800....any thoughts? I am getting about 45 on the gps, though. Could the Tach be off?

[PerchJerker]

the extra blades make a big difference when it comes to holeshot and cornering.

marine_man

That's why I really like my Rev 4 prop, really good compromise of speed (fewer blades) and handling (more blades). And those BIG blades on the Rev 4 do a really nice job of handling a heavy load in the boat.

Setterguy - it's possible your tach is off, and someone that's mechanically inclined like marine man or valv or the others will be able to help you out. Other things to check as we noted are your motor mounting height, having it too low robs performance, and the prop. 13 3/4 sounds like a small hub prop (so probalby small blades too??), maybe a larger diameter / larger bladed prop would work better on your boat.

[marine_man]

What do you have for a Tach? Is it a yamaha brand tach, or is it a generic (teleflex, etc). If it's a yamaha brand tach I'd be surprised if it's off.. that happens pretty rarely on Yamaha tachs from my experience. If it's not the only way to check it is to have a meter that measures it or hook up another tach and compare the two.

I agree with Perchjerker too - a bigger hub prop may be more what you might need.

marine_man

[setterguy]

It's an alumacraft boat I'm assuming its the generic tach that they use. I also forgot to mention that mine is not a HPDI it is a four stroke. When you say larger hub, does that mean going to like a 14 1/4 or 14 3/8, should I stay with the same pitch of 21 or go up to a 23 or something? Excuse the ignorance, I have no clue when it comes to this stuff. The boat is new to me since October of last year so I'm still learning the ins and outs of the boat. The motor is mounted on the second hole from the top. There are four holes.

[marine_man]

A couple of things here then...

Since yours is a 4-stroke the upper end of the rpm range is 6000 - that'd be my target for you running in your boat with a lighter load.

That said, you need to bump your rpm's by 1,000 rpm. I'd see what hole your motor is mounted in and go to at least one hole up from the lowest spot. Then you'll need some propping help.

What is your holeshot like? Not so great?

You're going to need to go down in pitch size.. but I'd see if a larger diameter prop is available for your rig - like you said, going to a 14 1/4 or 14 3/8 and probably dropping to a 19 pitch prop at a minimum. You drop pitch to raise RPM's and vice versa to increase rpm's. By going to a larger diameter hub you're able to get bigger prop blades and that'll help the RPM situation.

I presume your 5,000 RPM reading is fully trimmed out, running at WOT?

marine_man

[setterguy]

Yes 5k at wot trimmed up two guys, normal load. Ok, if mine is mounted in the second from the top and there are four holes, I should drop it down one hole? Then try to figure out prop size is needed?

Thanks MM, you are a great resource here for us knuckleheads.

As far as hole shot, I guess it's all relative. I've never had this big of motor, it seems to plane out fairly quickly. I just don't really have anything to compare it to ya know?

[eyepatrol]

This is a great discussion thread. Sure does help me out to understand the mechanics of it all.

[marine_man]

Sorry.. my hole description wasn't so good. What I meant is one hole up from the mounting position that puts your engine in it's lowest spot. That said, it sounds like you're in that location.

You could go higher, and there likely wouldn't be anything wrong with that... but I'm kind of stuck in a "if it works stick with it" rutt when it comes to motor height.

Anyway, I'd start exploring some prop options at this point. My gut feeling is that there shouldn't be any reason you can't get by with a 21 pitch prop on that boat.. but evidently that's not the case.

When you put the throttle at WOT on holeshot does it pop right out of the water or take a bit to get up and on plane?

marine_man

[BoxMN]

I don't know that much about 4 strokes, but from the reading and seeing other discussions about them, and seeing that your RPM range is to 6k, I would say they need (in general) much lower pitched props than I am used to. I bet that you might even find yourself into a 17" or 18" or maybe 19" on that boat. Not sure what gear ratio you have, as that comes into play as well, making it different from my 2 stroke and other engines.

Usually I think dealers will mount the motor one hole up (meaning one hole from the lowest position, in my speak, I guess I speak moe about the bolt position). I think that if you findthe right prop, that is often too low and raising the motor one hole gets you better performance.

Someday I will try a 4 blade like PJ uses, but on our boat the Tempest just works just as good as the Hi-5 but a bit faster (about 3 mph) so no real need. It still jumps out of the hole like a rocket, and for you guys with the TS175 and 150hp motors, yours should too when you find the right prop for the motor.

We did test 3, 4 and 5 blade props in different styles and pitches before we found ours. The 21" Hi-5 and 19" Tempest work best for us, but the 21" Tempest was fastest, but rpm's too low. We also tested all but the Tempest on two hole settings. Whatever you do, don't even bother with a Laser prop on this boat...

[LMITOUT]

I agree. It sounds like a smaller pitch is in order to get RPM's up, or if the holeshot is very good right now a cheap and dirty test would be to bump the engine up a hole to gain a few RPM's that way and see how it performs then. If that works and the holeshot isn't affected too much or you can live with it, then a step down in pitch may bring up the RPMs even a little more. When the holeshot starts to suffer or blowouts begin, then you've gone too far. You'll have to sacrifice something to gain in other areas of performance and finding that fine line is the holy grail of what you want out of your boat.......speed, handling, holeshot or a balance of all three.

If you can line up some test props then I'd start there first as that's pretty easy to try without monkeying around with a heavy engine. If that gets nowhere then bump up the engine a hole and try the props again.

I have a 90HP four stroke Yamaha and there is a wide variance in set-ups between that and other four strokes in that class for my boat. There are guys running the same sized Suzuki engine and running 21 P while I'm running a 16P...mostly because of the gearing difference between the two brands as the Yamaha is geared a little higher than the Suzi's.