Friend of mine has a 1986 Stratos 189 powered by a 150 Yamaha mounted on a jackplate. He tells me when he trims up on the motor it fails to lift the bow of the boat. He has tried a 25 Pitch prop and now is using a 26 Pitch. (Both stainless 3 blade). How high should the motor be mounted on this hull to obtain the lift he is looking for? Thank you.
Hes a little under power the boat is rated for a 200 HP . He may also over prop to with a 25 -p prop . I would try a Tempest plus 23-p or Yamaha 23-m .
Iwould start at 3.1/2 below pad both of these props has good bow lift.
How many RPMs at WOT? A 26 sounds like WAY too much prop for that combination. Bigger isn't always Better when it comes to props.
Thanks John for the post. I have now joined the site. I'm the boat owner, Too answer your question I have only ran the motor around 4500 RPMs because the bow is digging into the water. I just replaced the piston and rod in # 6 so I don't want to be too rough on that repair. On the transome, you have the very bottom of the boat at the drain plug, above that you have what looks like a false bottom, maybe called a step?? Where should the cav plate be in relation to the just mentioned. V/R elbob
OK ... this should help get you started:
Start with your prop-shaft 3.5" below the pad. This should assure that you aren't too high. If the boat still fails to lift the bow with it trimmed up 1/2 way on the trim gauge at the mentioned 4500 RPMs, then you have a problem. I suspect that the 26" prop you are using is WAY too much prop for your boat. I'm not real familiar with the 189, but I would think that a 23" or 24" 4-blade prop would be a good place to start. Also, it is going to be very difficult to select a prop until you have the ability to run at full throttle and see where the RPMs are. I'm not a Yamaha guru, so I'm going to be guessing when I say that you should be running 5000-5300 RPMs at WOT and trimmed up 1/2 way on the gauge.
My first inclination is that the prop is WAY too big and causing much of your problems.
Thanks for the Diagram. My prop shaft is about 5 to 6 inches below the very bottom of the boat. I lowered it because someone suggested that lower the engine more water for prop to digg. Little back ground. I've had this motor raised to the max , in between and now at the lowest. What kinda puzzles me,, is no matter where the setting the hole shot is QUICK with 26 and 25 pitch prop. never indicating a struggle to turn those props. You would think I was turning a 21 to 23 pitch. I'm at 4500 rpms at 3/4 throttle so Guessing from this point that when I get the nose up and at WOT i'll be up around 5500 rpm. The motor has around 90 psi in each of the 6 cylinders I wonder what it should be and if it's enough to produce 150 hp???
My best friend lives in Flordia he owns Charlies Fishing Hole bait Shop his name is Chavis Chuck Chavis. any relation?
Does the bow rise at all when you start to trim it up?
Where the motor is setting now it lifted a little. With that said, the water is breaking about 3 foot past driver console toward the front both sides. Which tells me the bow is still down. Too much trim i'm throughing a huge rooster tail, bow down. I trim down alittle no rooster tail,, bow appears to get a little better but still front of the boat it breaking water. V/R Bob
I was told by a fellow that used to race boats,,, that was a badly designed hull and I would never get the bow up. Just hard to believe
<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by elbob54 »</td></tr><tr><td class="quote">
I was told by a fellow that used to race boats,,, that was a badly designed hull and I would never get the bow up. Just hard to believe</td></tr></table>
..... the boat will lift, you just have to get it set up right.
Without seeing the boat run or driving it, and based on the info you've given, I would at the very least try a different prop. A smaller pitch would be my suggestion. Adjust the motor to 3.5" below the pad, and try running a 23 or 25 pitch 4-blade prop. I'm not familiar with the Yamaha prop offerings. I know that there are 150HP motors out there that perform with 26" props, but they are few and far between.
Hair jig to directly answer your last question there is no real noticeable lift throughout the trim up process. V/R Bob
Prop too big. Go to a smaller pitch.
The trim on the motor creates lift through a "lever" effect. If the engine can't create horsepower, it can't lift the boat. If the prop is too small, there is no "muscle" ... and if the prop is too large, there is no "momentum". Did that make sense? Your engine can't lift the boat because it's struggling to turn the prop that is too big.
At least that's my take.
Just to make sure I'm understanding the diagram in terms of "pad". Your diagram marks the transome, and pad. When relating this to my boat the PAD location in your diagram looks like the very bottom of my boat. Does this sound correct? V/R Bob
YEP.
The pad is the very bottom running surface, directly in the centerline of the hull.
I hear you about the prop pitch, but i'm strickly working within the confines of lodgic and I can't seem to get past the fact that there is no struggle with the hole shot or RPMs normally both are present if a motor can't turn the prop. So if you are right that I need a smaller pitch prop then it's technical not logical and I would be the first to agree that I could use a lot more technical understanding. I'll try it thinks for your help you are a true gentleman. V/R Bob
Like I said earlier ........
It's extremely difficult to diagnose something that you can't hear or see.
But based on your hull (heavy) and your horsepower (150) my first inclination is that you shouldn't be trying to turn a 26" pitch prop. That's just WAY too much wheel for that combination.
Do you know anyone with a smaller prop that you can borrow for an afternoon?
Yeal, Troubleshooting is hard the way we've been doing it. I'm sure if you could touch the problem you could fix it. Atleast by hanging in there with me you've given me a bit of incouragement in the smaller pitch prop idea. The local prop shop guys are very good about lending out test props. I'll keep you posted. V/R Bob
One other thought ......... EXACTLY what brand/model prop are you running?
Please don't tell me it's a chopper-style prop.
i would think with a chopper style it would blow out too bad to have a hole shot without laying on the front.
with you turning those big props easy on hole shot and no bow lift,i would say you may have some props that have little to no cup,or something like an all purpose ss prop,does it have short ears and no rake,someone may have done a backyard file,grind job etc or like a24 raker i had redone,wasn't worth bolting on.i fished out of one of those for 3 years and drove it for miles,while it had a 2.0 200 merc it would run high 60's and bow lift was not a problem,and neither was hole shot,it turn a turbo 2+2 in 24 pitch if remember correctly.with the 150 i agree with others,you should be in the 23 range max,unless it is a very stout 150.
as far as a bad hull,with a good 200 on it,3.0 200 rude or a 200 prov that boat will run in the 70's easy with a 25\26 prop.
HULAPOPR, you're think the same thing that I am. Either a big-eared prop, or one with no lift. Either or both aren't good.
Both are Mercury Props that came with the boat. The 25 pitch is a Lazer 2?? the 26 pitch has no markings. Will say it looks like the lazer 2 both are 3 blade and the cup looks good on both. Everything around here is closed until Jan 2nd. I will persue a 23 pitch test prop and post my findings. V/R Bob
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