Not sure I want to post this but proves a point.

[Texasmark]

Recently got back into boating with the purchase of a 2002 Crestliner 1750 and a 115 Merc 2 stroker. Purchased from a rather large dealer of such and the engine had gone through the shop with the mechanic being a seasoned professional. It was obvious he had been through the engine. Compression was 129 on 3 and 131 on the 4th (he marked it on the water jacket cover).

Prop was a Ballistic SS 22XP and wasn't ported. I doubt the prop was what was on the boat initially as my first time out it was a dog out of the hole with just me and it took forever got up on plane and you could tell the engine was straining. I forget the speed and RPMS as I was concentrating on what it would take to fix the problem. Something was drastically wrong.

In applying my experiences over the years with similar boats and having run the Ballistic 24XP on the boat pictured in my Avatar, and having experience with the Turning Point Hustler Aluminum which is ported, I installed a 19P Hustler.

Idle to bow down 30 mph plane was 3 seconds! 3 inches of pitch reduction helped but didn't do that.....the porting did....and even though the TP is a premium Alum. prop, it still had thick blades as compared to the Ballistic and other SS high performance (non racing type) props.

RPM recommendation for the engine is 4750-5250 and at best trim, no wind or waves, I was running 4850 at 38 mph. Go-fast.com prop slip calculator said my slip was 14% so my (new Farina tach) must have been right on (was at 2000 when checked against my digital shop tach). The Crestliner is over 7' wide, 12* rise at the stern, and has reverse chines which allow it to set up really dry (not a lot of hull in the water) at WOT.

I like to run at the top or slightly above the recommended engine RPM range but for now I'm going to leave it be since the engine seems to be happy where it is and ¾ to full throttle gets an immediate response. If I were to fish with others then I'd drop down to a 17P which would set me up for 5466 RPM (per Go-fast) if the other conditions remained the same....and why shouldn't they. Since TP props are less than a hundred bucks here, I might just do that....hope I don't pop my neck on the hole shot. Grin

Point to all this jibberish is that MY experience with 2 strokers is that they have no torque (to speak of)since they are 2 strokers, (bang runs out half way down the power stroke) run 1 hp/cubic inch nowadays and to get your HP to twist your prop shaft so that your prop will develop the thrust needed to push your boat out of the hole you need RPMS.....HP is [Torque (in Ft-Lbs) x RPMS/5252]. Ports help you get those RPMS fast when you need them most!

 

[BaileysBoat]

Good advice mark......The TP Hustler is an awesome prop.

 

[flyingscott]

Point to all this jibberish is that MY experience with 2 strokers is that they have no torque (to speak of)since they are 2 strokers, (bang runs out half way down the power stroke) run 1 hp/cubic inch nowadays and to get your HP to twist your prop shaft so that your prop will develop the thrust needed to push your boat out of the hole you need RPMS.....HP is [Torque (in Ft-Lbs) x RPMS/5252]. Ports help you get those RPMS fast when you need them most!
Trying to wrap my head around this statement. No torque to speak of??? Must have ported props???? Because outboards are more than 1 hp per CI can't make torque???? HMMMM

 

[jimmbo]

If 2 strokes have no Torque, then 4 strokes must in the Minus ft lbs. Of course 2 strokes have Torque.

 

[Texasmark]

If 2 strokes have no Torque, then 4 strokes must in the Minus ft lbs. Of course 2 strokes have Torque.

Figure of speech. Grin All my tractors are under square 4 stroke diesels. To name a couple they run 4 or more cu in per hp. They can tug but run at 1800 for some and 2600 for the newer ones...fewer cubes.

 

[Texasmark]

Good advice mark......The TP Hustler is an awesome prop.

TP says that they are the only mfgr. of alum props that are ported......too bad the other guys are missing out on this superb hole shot assistor. This is my second; different rig. Not sure what this boat wanted and wanted something cheap to find out.

 

[flyingscott]

The OP has more holes in it than the block of swiss cheese in my fridge. lol

 

[jimmbo]

TP says that they are the only mfgr. of alum props that are ported......too bad the other guys are missing out on this superb hole shot assistor.

Poppycock, OMC/BRP have many AL props that are vented

 

[flyingscott]

Ok lets really look at whats happening here. You bought a motor ,put it on your boat found out it was over propped. So your holeshot sucked pretty normal stuff. Dropped 3" of pitch went from SS to aluminum and a vented prop. So with no other testing all of a sudden those holes are are what improved your holeshot. For this to hold any water for me at all you would have needed to vent your current stainless prop and document the difference in hole shot. Have you tried a non vented prop? How do you know that wouldn't be better? Have you tried playing with the hole sizes on the vents? For a fair comparison should you not have put a vented SS prop on. So do this plug all the vent holes on your prop and test it that way. This is one of the worst comparisons I have ever seen written. You were right you should not have posted it. By the way you are still slightly overpropped. Why don't you put one of your Diesels on the boat?

 

[QBhoy]

Hi there. Interesting post. Excellent. 2 strokes are known for their torque to be fair to them.
But most of all I’m replying because I’ve had a bit of experience with the ballistic.
The ballistic is a total hit or a miss. But not just in the usual way. I had one in my own boat for a while. It is without doubt capable of incredible result but not consistent or day after day. It very much depends on conditions. You also need enormous power to weight ratio and a hull capable of airing right out. To be clear when conditions were right it was ridiculously quick on my boat but not al the time.
Compared to the enertia and laser 2 of the same pitch it was slow to get on plane and seemed not too happy at cruising speed. It would try and fall off the plane at lower rpm compared to the above mentioned. It was only happy when close to or surfacing. But contrary to the normal rule of thumb (as in slow to plane would see lower rpm at top end) it would allow the engine to see higher rpm at wot than true other 2. But only if conditions were right. As in running light and a bit of chop and air under the hull. If I had anymore than a couple on board it would struggle and be a bit of a dog all through the rpm range. The enertia is a better prop on most occasions

 

[Texasmark]

Poppycock, OMC/BRP have many AL props that are vented

As I said: "they claim......".

 

[Texasmark]

Ok lets really look at whats happening here. You bought a motor ,put it on your boat found out it was over propped. So your holeshot sucked pretty normal stuff. Dropped 3" of pitch went from SS to aluminum and a vented prop. So with no other testing all of a sudden those holes are are what improved your holeshot. For this to hold any water for me at all you would have needed to vent your current stainless prop and document the difference in hole shot. Have you tried a non vented prop? How do you know that wouldn't be better? Have you tried playing with the hole sizes on the vents? For a fair comparison should you not have put a vented SS prop on. So do this plug all the vent holes on your prop and test it that way. This is one of the worst comparisons I have ever seen written. You were right you should not have posted it. By the way you are still slightly overpropped. Why don't you put one of your Diesels on the boat?

The engine was OEM to the boat. I just bought it from a dealer and know nothing about the prop that the previous owner ran. I really doubt he ran the one that came on it. Agree on the near surface running of the TP. At 4 holes up it didn't loose bite even in hard turns, nor blow out at high trim angles. On my previous boat with a stepped hull and one hole up, it bit just fine. No, the Ballistic is not ported.

Thing I didn't point out was the engine is a 2+2 and getting from 2-4 takes quick rpms if you want a blast of power out of all 4 in the hole. The ports suffice for that. Of course the pitch change helped but that was a somewhat linear thrust increase, not a stepfunction.

To play with the hole size you need JB weld or a drill. Not a Mercury Laser II.


Yes I was slightly overpropped. I said I was guessing at what pitch the rig wanted and looks like I was 2" higher than I wanted to be.
Bought a 17 which just put on today and will test sometime mid week and get back here. Interested if the numbers are accurate about usable thrust equals pitch x rpms x slip. If so, with the exact same prop with only the pitch reducing by 2" I should get my rpms up near the top rating (5250) keeping the same slip and boat speed at WOT with even a better hole shot. Expecting to loose a little speed at mid range but have better control on the engine rpms.

On putting a diesel on my boat (neat idea....wink), I need them in my tractors. I have hay on the ground right now and as soon as the weather clears enough for it to dry out I'll be using all 5 to get it up.

 

[Texasmark]

Hi there. Interesting post. Excellent. 2 strokes are known for their torque to be fair to them.

Really? Then why did Merc up it's 150 from the original 2 liter to 2.5 liter...like in the 1997 Merc sales brochure it lists the 150 at 1998 cc and the 150 Magnum at 2507cc (121.9 vs 153 cu in)............the 150 was having a hard time getting arse heavy bass boats up and out.

 

[QBhoy]

Really? Then why did Merc up it's 150 from the original 2 liter to 2.5 liter...like in the 1997 Merc sales brochure it lists the 150 at 1998 cc and the 150 Magnum at 2507cc (121.9 vs 153 cu in)............the 150 was having a hard time getting arse heavy bass boats up and out.

The 2.5l merc magnum was a limited run for certain purposes. It wasn’t just a case of upping the displacement for lack of torque. I’ve a 150hp 2.0 merc V6. It sure isn’t lacking on torque. A 2 stroke motor of any HP will always have more torque than 99% of equivalent 4 stroke. That’s why all the money in 4 stroke development has went into developing more torque from the 4 stroke whilst trying to keep the weight on a par with a lighter 2 stroke. Hence the reason that most big power 4 stroke outboards these days need forced induction to produce the HP and keep the weight down. This is the first time I’ve known anyone to say a 2 stroke lacks torque.

 

[flyingscott]

Take the transmission off of your diesel and make it run through a straight overdrive. Then tell me how well it does because that is basically what an outboard has to do. I had one of those motors I never had a problem with holeshot I pulled 5 skiers out of the water with mine. I ran a plane jane quicksilver aluminum prop no holes 19" pitch. I gotta say I always thought you were a little more knowledgeable than this.

 

[Texasmark]

I had a 1972 Johnson 125 on a '72 18' Caravelle tri-hull bow rider and did 5 too just to see if I could do it at a company picnic one Saturday. We made a couple hundred yards before one fell off which tanked the stunt for the rest of them but it did it and as I recall I was running a 19P 3 bladed OMC SST (Stainless Steel Teflon) which came out in '73. No ports in it.

I never ran a hull like the current one and have no experience with it so don't know what to expect. It does really ride high and dry for a non padded hull. Same with the engine. On a learning curve.

I got into ports back in 1989 when I bought a Ranger pad hull with a 115 tower and it came with a laser SS which was ported. Gave me a great hole shot and when up to speed you could feel the holes close off and the prop bite the water, rpms dropped initially and the speed took off. Have liked them ever since.

 

[anzomcik]

Point to all this jibberish is that MY experience with 2 strokers is that they have no torque (to speak of)since they are 2 strokers, (bang runs out half way down the power stroke)

I understand what your saying, but help me out....

As you say 1/2 power stroke per 1 revolution for 2 stroke, i agree

Tell me how that compares to 1 full power stroke per 2 revolutions on a 4 stroke....

Correct me if im wrong, but doesn't each motor design get 1 full power stroke per 2 revolutions (2 stroke .5 + .5 = 1 per 720 degree rotation) vs (4 stroke 1+0=1 per 720 degree rotation)

I fully understand the workings of the each motor, I understand the bottom line of your post. I just wanted to add the other side of the story that wasn't mentioned.

 

[flyingscott]

So a 2 strk only has a 1/2 of a power stroke. WOOOOOOOOOOOOOW

 

[Oldnbold]

Y’all are kind of harsh on Texasmark and his assessment of the 2stroke torque.
my assessment of 2stroke torque vs 4 stroke torque is the 4 stroke puts out more linear torque on a rpm curve than the 2stroke but less of it given equal displacement.
the 2stroke has an optimum powerband,aka Rpm range . If you’re not in the powerband the engine is sluggish. Porting the propeller gives enough slip to allow the rpms to quickly get into the powerband hence a much better holeshot.