Correct Prop Size for 28TE

[cpesce]

I have the 1997 28 TE and my boat is not getting up to the rated RPM. It may be over propped but i have no idea as to what the factory spec is for prop on this boat. Any ideas? Thanks for your help.

[Cape Codder]

My 2003 with a Yanmar 315 has a 19" x 19" 4-blade

[jcollins]

You didn't mention which engine? Does it matter?
Mine is the 18x18 3 blade. Peninsular.

[RobS]

You didn't mention which engine? Does it matter?
Mine is the 18x18 3 blade. Peninsular.

Yes, both the engine and the tranny ratio matter.

[Russell]

The props on other boats can only give you an estimate because of added weight and windage of things mounted on the pilothouse. What you should do is make sure your propeller and bottom are clean. Then fill your tanks and take some people with you if you usually have guests. Determine the boat speed and RPM you get at wide open throttle and take this information and prop to a propeller shop. They can analyze the prop and knowing the type of boat make a calculation of what the pitch and cup should be. An experienced prop shop can do this pretty well and change the pitch and cup if the prop is in good shape. If you are not certain your tachometer is calibrated, purchase an inexpensive phototach. I purchased mine on eBay but there are other places to get them.

[cpesce]

Thank you for the replies. I have "The Beast", Peninsular 300HP.

[RobS]

From what I recall and as John has posted above, the Penninsular TE's had 3 bladed 18" diameter props. As far as proper pitch and cup, that's gonna be based on "your" boat. Russell couldn't have explained it better. Will likely be in the 18 to 19" range on the pitch depending on any cup in the prop and the specifics of your boat (weight, windage, bottom condition, etc)

[jcollins]

Thank you for the replies. I have "The Beast", Peninsular 300HP.

I have the Hurth 1:56 to 1 transmission. Yours is possibly the same since we have the same engine and the year of our boats are close.

[Capt Paul]

You also need to take in to account the accuracy of your TACH. You didn't mention how you measured your RPM, but my mechanic told me if your dash board mount tach is within or around 200 RPM of spec, I should not be overly worried about it. I still have not had my TACH RPM accuracy checked but need to do it. I am supposed to get 3800 RPM at full throttle with the engine/tranny combination I have, Dash board tach consistently shows a little over 3600 RPM.

Paul

[RobS]

I have not heard too much about the Pennisular tachs being off a much as the Yanmar tachs. The Yanmar factory tachs are the worst for accuracy. In the higher rpm range my factory tach reads 200rpm's high and it's not adjustable. Here's the photo tach unit I purchased. Works very well: http://www.tequipment.net/Extech461920.asp Either way, I agree, the engine should be photo tached to prove, or disprove, the accuracy of the tach.

[Russell]

Your might try this one for $29 at Amazon. http://www.amazon.com/Digital-Laser-Pho ... B000EUT9ZS
I purchased one for a similar price on eBay and it is a good thing I payed so little or I might have had a heart attack. I went out by myself to check the speed and RPM at WOT. I tied the engine box up so it would not come down on my hands in a wave and set the phototach down on the deck so it would be right where I needed it. When I got up to speed I walked back to do the test and the phototach was gone. I looked around and there it was in the salt water in the scupper drain. Luckily it still worked after I took it apart and cleaned it up. The electronic part did not get wet, just the lens. My Cummins tach reads about 50 turns low at 2600.

[cpesce]

My tach might be off and I'm definitely going to photo tach it to check but my boats not even close to getting to rated speed (3,800). I'm barely getting 2,800 and she doesn't smoke a lot of black smoke so i doubt it's the prop size/pitch but I'm exploring all possibilities.

Thanks for the tip on the photo tach, just ordered the one from amazon. We'll see...

[DougSea]

My tach might be off and I'm definitely going to photo tach it to check but my boats not even close to getting to rated speed (3,800). I'm barely getting 2,800 and she doesn't smoke a lot of black smoke so i doubt it's the prop size/pitch but I'm exploring all possibilities.

Thanks for the tip on the photo tach, just ordered the one from amazon. We'll see...

I'm pretty sure the rated top end for the Penninsular is 3600 and that's your target for WOT.

I'd be fairly suspicious of your prop. Can you get to 3600 in neutral? That will help narrow it down.