new prop for 28 express 315 yamar

[saltshaker28]

I just put a new prop on my 28 express I have a yamer 315 in her h h props sent me a 19by 18 but when I haled the boat I found out I had a19 by19 on her does anyone have a 19 by18 on their 28 running a yamar 315 I would love to know why they sent me the wrong prop

[furball]

saltshaker28
I have a 2006 flushdeck with a original 19x18 prop. I am considering going to a 19x19. My Floscan reads 4050 to 4100 at WOT with full tank and loaded. Beede tach reads about 100-150RPM lower. First I need to confirm which tach is correct? At 3800-3900RPM my SOG is about 20Kts, 3600 gives me about 18Knts. I think I could use a little more pitch to bring WOT RPM down and speed up a little. I plan on tracking the numbers closely through the end of the year and make some changes this winter. What our your WOT RPM's and SOG at cruise and WOT with a 19x19?
Good luck
John

[RobS]

I just put a new prop on my 28 express I have a yamer 315 in her h h props sent me a 19by 18 but when I haled the boat I found out I had a19 by19 on her does anyone have a 19 by18 on their 28 running a yamar 315 I would love to know why they sent me the wrong prop

They should have asked you what prop you had now, what engine and what rpm's you were turning. Did they just simply send you the 19x18? Not saying it's wrong but they should have obtained some specs from you in determining the correct prop in case you either needed to get back or give up some rpm's to be at the recommended WOT. Is it a 3 or 4 blade? What was your WOT rpm before and what is it now?

[RobS]

saltshaker28
I have a 2006 flushdeck with a original 19x18 prop. I am considering going to a 19x19. My Floscan reads 4050 to 4100 at WOT with full tank and loaded. Beede tach reads about 100-150RPM lower. First I need to confirm which tach is correct? At 3800-3900RPM my SOG is about 20Kts, 3600 gives me about 18Knts. I think I could use a little more pitch to bring WOT RPM down and speed up a little. I plan on tracking the numbers closely through the end of the year and make some changes this winter. What our your WOT RPM's and SOG at cruise and WOT with a 19x19?
Good luck
John

Photo-tach it and go from there. If your Beede is accurate I'd leave it alone. I have the 4 blade 19x19 and turn less rpm than you. My tach reads 3900-3950 WOT fully loaded which would be perfect if the tach were accurate. I photo-tached it twice with different units and find that my tach reads +/-125rpms over the true rpms which is the norm for the Yanmar tach and it is not adjustable. Therefore, I'm just turning 3800 at WOT. So I will probably do the opposite of you and take a half to a full inch of pitch out the prop this winter to get back 50-100 rpms.

I don't have my data with me but I'd say I'm about 2 knots faster than the numbers you mention. Of course there are factors involved, tide, etc.

If you need to give up some rpm's you should find out about adding some pitch or cup to the prop as opposed to having to replace it as I'm sure it would be a big savings.

[furball]

RobS,
The Beede tach was set 1 tooth less than it should have been, pins set for 116 tooth flywheel, I changed it to 117 per Mack Boring. Still less than a 1% change. My Floscan reads higher and I'm hoping to check the setting on the two dials on the back this weekend. Next step, photo tach to see which is closer to true. My manual for the 6LP-STP says 3800 WOT. sounds like your right on it. How much pitch can a prop shop typically add or take out of a prop? I want to pull it this winter and have the prop scanned and tuned if they can change it that much, I'd perfer to do that instead of buying a new one.
Thanks,
John

[RobS]

When I checked the tooth count on my tach it was off by one tooth, don't recall the numbers. But like you said it's less than a 1% change (actually 1/116) The prop shop would have to examine the prop to see how much it can be re-worked, pitch, cup, etc. depending on it's current pitch, cup, etc. but my guess would be that it's a stock prop so they would be able to work it enough to gain the results you need without replacing it. An inch of pitch = 100rpms is common.

[Carl]

Furball, I see you are in Md. Black Dog Props is a prop scan shop on Kent island. They took my 19 X 18 and made it a 19 X 19. Mine is a 2006 flush deck and came with the 19 X 18. This took my WOT from 4250 down to 3950 with a clean bottom. I gained about 2 knots from a cruise of 14/15 knts to 16/17 at 3400 RPM. Hope this helps.

[RobS]

Furball, I see you are in Md. Black Dog Props is a prop scan shop on Kent island. They took my 19 X 18 and made it a 19 X 19. Mine is a 2006 flush deck and came with the 19 X 18. This took my WOT from 4250 down to 3950 with a clean bottom. I gained about 2 knots from a cruise of 14/15 knts to 16/17 at 3400 RPM. Hope this helps.

Now that what I'm talking about - nicely done...

[furball]

Carl,
Thanks for the info. I'll give Black Dog a call. Sounds like just what I need.
saltshaker28
Sounds like the move to 19X18 will cost you some speed, something I wouldn't want to give up!
Anyone know if the cheaper photo tachs are worth buying? I see some for around $50-$60 and then in the $200 range. I've checked with most of my friends hoping for a freebie, no luck
thanks
John

[Carl]

You can go to their web site at blackdogprops.com and print out a form thay you need to fill out before you do anything. The more info you give them on that form will save time down the road. When you get it back you will want to hang it on the wall it will be so pretty!! Around 300$ and well worth it.

[RobS]

Anyone know if the cheaper photo tachs are worth buying? I see some for around $50-$60 and then in the $200 range.
thanks
John

I am a firm believer in you get what you pay for. For the amount you would use a photo-tach I do not think it would be worth the investment but when you do feel the need to use one it's certainly imperative that it's as accurate as possible. In my opinion it's an item where accuracy is the need, not convenience of being able to use it regularly. You should be able to find a local mechanic who could shoot it for you for under $100. The mechanic I know who shot mine paid over $600 for his unit....

[furball]

Finally got around to checking my Floscan settings and it was set-up for 113 teeth on the flywheel. Changed it to 117 and went for a short ride. Both my Beede and Floscan now match, +/-25 rpm
Plan to give it a good run Sat and record my RPM/fuel/speed numbers now that I'm confident they're accurate. I'm not so sure about adding pitch now. Carl, I think my rpm/speed numbers will be about the same you mentioned.
John