change prop, mounting hole, or both

[Eazy Mony]

Well I am getting 3 for 3 telling me to move the hole first, your experience and reasoning make a lot of sense. It is a new engine with low hours, just had it serviced and it will turn the 5900 rpm. I called Hewescraft direct today, and they confirm it should be able to turn a 17P with proper setup. I checked all of the Yamaha Performance bulletins that had a F150, 2 boats close to mine...22ft Searunners, both are using a 17P Reliance SS prop and using hole #2. I also just found the 15P is not recommended for the F150. So, I have the boat on a trailer in my driveway...looks like moving the hole is first project. SkinnyRaven, hope you report back on your next outing in hole #3, and thank you for the lesson on prop slip, i have already learned so much from this forum.

[Eazy Mony]

BaileysBoat was spot on with how easy it is to change the mounting hole. My local dealer set my boat/engine up from new and it was really buried, which I gather most dealers do as it lessens the cavitation in corners for inexpierienced drivers.
I lifted my outboard using the method described by BaileysBoat and picked up almost 400rpm, switched to a better pitch prop and is now a much better performing boat (speed, cruise and fuel economy). Have a look at the Mercury prop web-site, they really hammer home setting the height right...

Cheers

You are the 3rd to zero in on the mounting hole...makes sense. Thank you for the comments and the point to the Merc prop site.

[BaileysBoat]

here is prop calculator;

Propeller Calculator / Prop Calculator

[Eazy Mony]

here is prop calculator;

Propeller Calculator / Prop Calculator

the web page would not load from here, i will try to search for the page outside of this thread.

Looks like my son and I have a weekend project waiting for us. change the mounting hole and record and document the results. I found a Prop shop in town that is willing to work with me after I make the hole changes. They also agree, make one change at a time. They are willing to let me try props in order find the correct prop even if it means swapping a few times and I dont bring one back that has been dragged along the concrete ramp.

I will report back next week some time and let everyone know the results. Thanks again to all for sharing the experinces and suggestions.
Howard

[SkinnyRaven]

When you calculate your prop slip with the information you have posted you will find that even though the rpm for the 17" prop is less than desired the efficiency is much better than the 15" prop. I spoke with Yamaha tech. support recently and was told that they would prefer to see the rpm's in the upper end but anything between 5000-6000 would do no harm. You can get an idea how far you need to come up if you can view the cavitation plate while underway. Each hole will give you approximately 3/4". I think once you get the engine mounted correctly the 17" prop will be fine. I am also talking with A1 Props.

[rodbolt17]

trust us, at the end of the day that engine MUST be able to turn 5800-6100 RPM with the load its carring THAT day.
otherwise they tend to make oil.
ask that yamaha phone rep if they actually work on them daily and if they actually own an F150.
I do both.
proper set up is critical and yes make only ONE change at a time.
always remember when looking at the perforance bullitens.
if the test boat and your boat are not identical the results will vary widely.
on the test boat,how much fuel,persons gear and did it have an extra 200 pounds of kicker motor?
you would be amazed how much a hard top, curtains and kicker motors will affect performance when compared to the same rig without them.

[axolotl98]

otherwise they tend to make oil.

Can we clarify what we mean by that ?

[Eazy Mony]

trust us, at the end of the day that engine MUST be able to turn 5800-6100 RPM with the load its carring THAT day.
otherwise they tend to make oil.
ask that yamaha phone rep if they actually work on them daily and if they actually own an F150.
I do both.
proper set up is critical and yes make only ONE change at a time.
always remember when looking at the perforance bullitens.
if the test boat and your boat are not identical the results will vary widely.
on the test boat,how much fuel,persons gear and did it have an extra 200 pounds of kicker motor?
you would be amazed how much a hard top, curtains and kicker motors will affect performance when compared to the same rig without them.

Thanks Rodbolt17, that has been one of the challenges...finding a performance bulletin with my exact boat and motor setup. My goal is to definately hit 5800rpm minimum with a "normal" load when this is all said and done. The last thing I want to do is screw up this motor with an improper load/setup. I do appreciate the comments and the emphasis of one change at a time. you are correct to include all variables, especially the added componets of a kicker, I also found out when I called Hewescraft, the 2003 Searunner weight was about 200 lbs more for that model compared to current year. I took a look at the cavity plate with the engine all the way down, it is approx 1 1/2 inches below the bottom of the transom. The engine mounting hole seems to be the most logical place to start, so this weekend, we are going to hole #3 and the 17P alum. Weather permitting.

[SkinnyRaven]

Ok somewhat of a report,was able to test run Sunday morning after watching the wind and rain blow for two days. I am currently mounted in the top hole, last adjustment up. Now however the spray around the engine lower unit prevents me from seeing the cavitation plate. I think I am as close to correctly mounted as I am going to get short of drilling new holes in the transom, not inclined to do that. I can say that I was somewhat heavier loaded than the Yamaha performance bulletin, full tank of gas, fishing gear, Wife, the Weimaraner, and three chihuahuas. The engine mount alone has made a remarkable difference in rpm's (6100), handling (no more excessive steering torque) and performance (within 4 mph of the performance bulletin). The next step for me is prop testing to reduce prop slip.

[Eazy Mony]

Ok somewhat of a report,was able to test run Sunday morning after watching the wind and rain blow for two days. I am currently mounted in the top hole, last adjustment up. Now however the spray around the engine lower unit prevents me from seeing the cavitation plate. I think I am as close to correctly mounted as I am going to get short of drilling new holes in the transom, not inclined to do that. I can say that I was somewhat heavier loaded than the Yamaha performance bulletin, full tank of gas, fishing gear, Wife, the Weimaraner, and three chihuahuas. The engine mount alone has made a remarkable difference in rpm's (6100), handling (no more excessive steering torque) and performance (within 4 mph of the performance bulletin). The next step for me is prop testing to reduce prop slip.

That is very encouraging...we got the engine mount changed to the 3rd hole. It was a very easy chore, just like the directions said. Couldnt make it out this weekend, so plans to head out next Saturday.

[Eazy Mony]

06/27/2011

Well, it has been a few weeks of trial and improvements, so I thought I would post our final and best results in case anyone is tracking this thread.

I have to go all the way back to the beginning and correct a statement of using a 15P prop black stainless. I was wrong...it was Aluminum. Even tho I used the sound of taping the fins and hearing a distinct "ring" compared to the 17P prop black, which had a definate "thunk", it became so clear when I went to the Prop shop and we finally selected a 15P 4 Blade Solas Stainless. When I went to pick up the Stainless with one hand, it was quickly apparent I needed two hands to hang on to it.

So, final result...glad to report after all this research, and with the help of a local Professional Prop shop, I was able to match our boat to what I think is the best setup for our situation. I have to be clear here, everybody has a different setup and requirement for their particular boat and engine. With that, I can tell you we disovered we are running our boat with a "typical" load on the "heavy" side. Like I stated earlier, we finished with a 15P, 4 Blade Stainless Solas prop that had some "cupping" on the edges to help with slippage and more "grab" comming out of the hole. We also moved the engine mounting from the #1 hole to the #3 hole.

The results were absoutley amazing. The torque was instant, we were able to cruise easily at 26 MPH @ 4000 RPM, and 31 MPH at 4500 RPM, finally WOT...39 MPH @ 5700 RPM. Even going from 4500 RPM to WOT, there was still a significant torque and excelleration.

This was a great learning experince, and I really do appreciate all the earlier comments and suggestions. And of course, I am wide open to additional ones concering our final setup configuration.

Howard

[99yam40]

Still not hitting the 5800-6100 Rodbolt talked about, but are real close so make sure you keep your eye on the oil to see if it starts making oil

[Eazy Mony]

Still not hitting the 5800-6100 Rodbolt talked about, but are real close so make sure you keep your eye on the oil to see if it starts making oil

Thanks for the reply back, I value your input and Rodbots'...you guys are the real experts here. If I missed something else to try, or go back and check, sure would appreciate another tip. I really like the way this is performing now. Quick response, crisp excelleration, engine even sounds better, not laboring to reach the RPM's. Again, I will show my lack of experience here, but what exactly do I look for when you mention: making oil?

Howard

[99yam40]

the oil level will increase from dilution by unburned fuel seen in 4 strokes.
You can keep an eye on the oil level to see if it increases.

I am not an expert, but I would consider Rodbolt one.

[SkinnyRaven]

I would still look at the mounting height, I am currently running a 4blade 15pitch prop on mine and run at 6000rpm WOT, I'm also 2' longer with a hardtop and have to be several hundred pounds heavier than your setup. I may yet try a 3 or 4 blade 17pitch.