2005 Crestliner Sportfish 1750 with a Yamaha 115 4 stroke

[dustybaker]

You'll have to simplify that a little more! cavitation plate?

[dustybaker]

Where is your cavitation plate vertical in reference to the bottom of the boat?

Ok, a couple google searches gave me an understanding of what your asking. I'll check tomorrow when I can pull the boat out and remove transom saver. Should the motor be trimmed all the way down while measuring this?

[delcecchi]

Yes, pretty much. Doesn't make much difference as long as it is close.

[dustybaker]

ok, when trimmed down on the trailer the cavitation plate is level withe lowest spot on the back of the boat.(the bottom of the little rib below the plug.

[Savage Brewer]

That is right for a staring point.

Next step will need 2 people. Run WOT on plane, go to the back and see if the cavitation plate is above or below the water.

If the cav plate is fully submerged while running on plane WOT, you could potentially raise the motor. But be careful as raising the motor too far could cause starvation of the cooling system.

But as a general rule of thumb the cav plate being set even with the bottom would be pretty close.

[BoxMN]

If you start setup with an alum prop from the dealer (or whoever you bought the boat from), generally speaking you can raise the motor one hole, then work on finding the proper SS prop that matches. Dealers (again generally speaking) mount the motor in a "safe" height for the lowest common denominator, meaning the person who doesn't spend time finding the proper match... for anybody who actually goes through the process of finding the correct prop, they can raise the motor at least a hole and you will notice a difference for the better.

I even had our dealer raise the four stroke on my new pontoon last year a hole above their normal spot - because as I mentioned above, it doesn't matter what you have, you might as well get the best performance out of it, even if it is a pontoon! haha!

I am more familiar with 2 stroke 90's and 150's but would assume a 115 4 stroke fits in there, and my guess would be that you can run on the middle hole with a well matched SS prop. But yes, you need water pressure for the motor, but I highly doubt a 115 is going to starve for pressure on the middle hole with a normal fishing boat. Not enough umph to really get it out of the water, most likely... but that is only my fourth cent here Good luck.

[dustybaker]

Ok, with two guys and fishing gear it ran just shy of 6k rpms and topped out at 35. It was a bit windier today than the last time I was out...but not much. Final thoughts anyone?

So to sum it up I have a 17 pitch alumium prop, fully loaded with 5 people 5750 rpms and 34-36 mph.

With 2 people, 5900 rpms and 34-35 mph.

[Ufatz]

I would say you have no complaints. And how often do you fish five people out of a boat that size? Looks like you're good to go. Have fun.Be safe.

[aanderud]

while calling around the dealerships to get advice on what to go with I was told this setup should run low 40s mph. I only get 35 or so with two guys and gear.

What dealerships were you calling? If they sell Crestliners, they should know how fast they run. Pretty basic piece of knowledge to have on a boat they're selling

I have a 1998 sportfish 1850 with a 125 merc 2 stroke. I get 37 on GPS with 3 guys and 39 (occasionally touches 40) with flat water and 2 guys (with gear and gas and 3 batteries, etc). If you took out the trolling batteries, the trolling motor, and all the fishing gear, and ran it on lower levels of gas, I could see it going "low 40s" with 2 guys, but that's not quite a realistic way to run -- no gear and no batteries and low on fuel .

[Kyhl]

Stupid question because maybe I missed it. Is your reported speed from a GPS or the speedometer?

Something doesn't add up because it sounds like you are in the correct rpm range. I am surprised that a 17" prop would turn that slow on that set-up.

Going by my experience with an Alumacraft 175 with a Merc 115 4S, I have hit the rev limiter (6,500 rpm) using an aluminum 17" prop.

I would ask these dealers how their boats are set up to hit 40 (hole position, prop, trim) then compare it to your boat.

[Savage Brewer]

My unprofessional thoughts are if you are holding 5900 rpm at WOT, I would believe you are probably propped about right, A 2006 Yamaha F115 should have a 28/13 or 2.15:1 drive ratio.

Meaning at 5900 engine RPM, would mean the prop is turning at 2739 RPM.

A 17 pitch prop at 2739 should put you at a theoretical 44 MPH with 0% slippage or loss.

12% seems to be a good average from most boating sites would put you at 38 to 39 mph.

I dont know, if this is bothering you that much you might need to go shop a new motor. I see that your hull should be rated for a 150HP motor. Maybe a Merc OptiMax Pro XS 150 or an Evinrude E-TEC 150 would do it... But spending that much to gain 10 MPH, that would be your decision.

Yamaha's aren't known to be the fastest motors out there, even with that sail I love my Yamaha 4 stroke, reliable fuel efficient, oh and did I say reliable?

[dustybaker]

What dealerships were you calling? If they sell Crestliners, they should know how fast they run. Pretty basic piece of knowledge to have on a boat they're selling

I have a 1998 sportfish 1850 with a 125 merc 2 stroke. I get 37 on GPS with 3 guys and 39 (occasionally touches 40) with flat water and 2 guys (with gear and gas and 3 batteries, etc). If you took out the trolling batteries, the trolling motor, and all the fishing gear, and ran it on lower levels of gas, I could see it going "low 40s" with 2 buys, but that's not quite realistic.

I talked to two different Crestliner/Yamaha dealers(Rapid marine in Rogers and Ham lake) and a dealer that sells Yamaha motors/g3 boats.(Hannays)

Your boat is a foot longer, weighs almost 200 pounds more and has 20 more horse, ehich equals 4-5

mph?

[dustybaker]

Stupid question because maybe I missed it. Is your reported speed from a GPS or the speedometer?

Something doesn't add up because it sounds like you are in the correct rpm range. I am surprised that a 17" prop would turn that slow on that set-up.

Going by my experience with an Alumacraft 175 with a Merc 115 4S, I have hit the rev limiter (6,500 rpm) using an aluminum 17" prop.

I would ask these dealers how their boats are set up to hit 40 (hole position, prop, trim) then compare it to your boat.

GPS, my spedometer is about 2mph faster than GPS. I will talk to them and get more details. I noticed when taking corners while pulling a tube it sounds like the motor cavitates pretty easy.

[dustybaker]

My unprofessional thoughts are if you are holding 5900 rpm at WOT, I would believe you are probably propped about right, A 2006 Yamaha F115 should have a 28/13 or 2.15:1 drive ratio.

Meaning at 5900 engine RPM, would mean the prop is turning at 2739 RPM.

A 17 pitch prop at 2739 should put you at a theoretical 44 MPH with 0% slippage or loss.

12% seems to be a good average from most boating sites would put you at 38 to 39 mph.

I dont know, if this is bothering you that much you might need to go shop a new motor. I see that your hull should be rated for a 150HP motor. Maybe a Merc OptiMax Pro XS 150 or an Evinrude E-TEC 150 would do it... But spending that much to gain 10 MPH, that would be your decision.

Yamaha's aren't known to be the fastest motors out there, even with that sail I love my Yamaha 4 stroke, reliable fuel efficient, oh and did I say reliable?

It doesn't bother me terribly, Ijust thought if it was supposed to go x amount of mph, and doesnt something must be awry, and because Ineed a new prop anyway iI thought I would see what others thought before deciding. It may be a mounting issue or just misinformation from the dealers. As far as the motor goes. im very happy with everything else about it. If it came with no motor, id probably buy the same one!. The boat is rated for a 140, so I think my 115 4 stroke has got to be close in weight.

[Savage Brewer]

Oh I didnt know you were in need of a new prop anyways.

Is your current one damaged?

Solderblooms hooked me up with a decent Solas aluminum prop at a reasonable price. What I did is give the guys up there my motor model, width and length of my boat, and I went to a weigh scale and got the total weight with all my gear, batteries and a full tank of gas (plus another 500 pounds to account for two adults)

They sent me the right prop without a hassle. Also if there is considerable wear or any damage to your current prop that can affect your speed quite a bit.

Good luck on your decision.

[dustybaker]

Oh I didnt know you were in need of a new prop anyways.

Is your current one damaged?

Solderblooms hooked me up with a decent Solas aluminum prop at a reasonable price. What I did is give the guys up there my motor model, width and length of my boat, and I went to a weigh scale and got the total weight with all my gear, batteries and a full tank of gas (plus another 500 pounds to account for two adults)

They sent me the right prop without a hassle. Also if there is considerable wear or any damage to your current prop that can affect your speed quite a bit.

Good luck on your decision.

Its not damaged terribly, but has a couple decent dings and I figured i'd get a new one snd keep this for a spare.

[aanderud]

Your boat is a foot longer, weighs almost 200 pounds more and has 20 more horse, ehich equals 4-5

mph?

I don't know, let's say my extra 10 hp accounts for the weight/displacement differential. I'm not getting 40s unless I run the thing either low on equipment and fuel or with a big tailwind. The other variable is that I have no idea what prop I'm running. LOL. It

That being said, I don't see 38 or 39 being unreasonable for your rig, and who konws, if you throw a 19 on there you may hit the low 40s that they're talking.

[delcecchi]

I have a 1775 provee lund, which sounds pretty comparable. I got between 40 and 42 with a Merc 115 2-stroke. That's with a bow mount 24v, three batteries, a 9.9 kicker, me and all my tackle.

Just for reference. (I think it held 30 gallons of gas too)

[tlbigstump]

Not real familiar with the speed of Crestliner hulls but it seems slow to me. I have ran alot of boats with f115's and merc 115 4-strokes and they always do real close to 40 or better. 1800 pro-v tillers with f90's will do 37-38 fully loaded with a ss prop. Do you get any bow lift with that alum. prop. If not I would go with a nice yamaha ss prop so you can get some lift and more speed.

[aanderud]

Not real familiar with the speed of Crestliner hulls but it seems slow to me. I have ran alot of boats with f115's and merc 115 4-strokes and they always do real close to 40 or better. 1800 pro-v tillers with f90's will do 37-38 fully loaded with a ss prop.

They're not the fastest in the fleet, that's for sure, but they're within a few mph of the fastest (given the same engine). The fishhawk is a faster boat, given the same engine -- especially the single console version.

Wind resistance is one of the biggest factors that limit all fast-moving objects. For instance, a dodge ram SRT with over 600 horsepower can only go 150 mph -- even though it has twice the horsepower as some other smaller, more aerodynamic vehicles that can do 200+ mph. Basicaly aerodymanically limited. I don't see many 1800 pro-v tillers with full windshields that the sportfish has. Similarly, the single console fishhawk will be several mph faster (low to mid 40s probably in this configuration) compared to the full-windshield sportfish. And that's just the windshield considerations. Add in the hull deadrise differences and you have a completely different beast for a completely different purpose.

[311Hemi]

If I could do 38 consistently with my setup which was weighted down with gear pretty good, you should be able to as well if not better. It's just a matter on if you want to mess with props or not. You boat should be able to go faster with that engine, but it's up to each person how important that is. I tried 3-4 different props before I dialed it in.

Below was mine before I sold it, it had the 115 yami as well. And the SS prop made a big different in overall performance. With the aluminum prop I had on mine, I was not able to trim out fully before the prop would start to cavitate. I could trim out much more with the SS prop, which allowed for better performance.

If you trim out too far at WOT (wide open throttle) does your engine start to cavitate?

And, for me running an 18 pitch SS prop I was still able to pull an adult skier out of the water without and issue and with multiple people in the boat, so my hole shot was not bad.