WOT Question

[harrydohnert]

I was wondering if anyone could tell me how I could find out the WOT of my engine. It's a 1986 Sea Ray Weekender 230. I have a 8 cylinder Mercruiser engine (230 HP) and a Alpha 1 Drive. <br />Thanks.

 

[harrydohnert]

Re: WOT Question

The reason I ask is that I am trying to figure out what prop pitch is right for me. I am all the way down to a 15, and I still barely hit 4000 RPM's. Should I go down to a 13?

 

[jeff13601]

Re: WOT Question

I think you have other problems then the prop. When is the last time your boat was tuned up. I am not a pro with props but that v8 motor should turn more then a 15 pitch prop. Are you saying the prop is a 15 pitch or diamater?

 

[QC]

Re: WOT Question

HarryD,<br /><br />New boat for you? History? Has it ever ran higher RPM? Boat bottom condition? At what altitude do you boat? Oh, my personal favorite, do you know the tach is right?<br /><br />With what you have noted so far, you should go to an 11 inch prop . . . <br /><br />Mucho mas informacion por favor . . . <br /><br />BTW, welcome.

 

[searay3]

Re: WOT Question

I have a searay of the same vintage. My tach was never set up at the dealer or factory or wherever they do that stuff. The engine was not aligned and motor mounts set up properly. Got the boat used and the prev owner bought it new. Point is, LOOK at the back of the tach to make sure it is set properly. If it is not, look around the entire boat to make sure the dealer prepped it properly.

 

[harrydohnert]

Re: WOT Question

Thanks for your repsonses so far. A little more info. The prop is a 15 inch pitch, not diameter. I am not sure if the tach is set up properly. Never knew to check that. I had it tuned up. The bottom is in near-perfect condition. The boat was purchased from a guy I know from work. The guy was from Indiana, and had the boat on a lake in Indiana. I live in New York, near City Island, so the boat is now in Salt Water. I just had the boat worked on. I used to get over 4000 RPM's on the boat when I first purchased it last year. I messed the prop up, and could not read the numbers off the prop, so I have been experimenting with different size pitches. I tried a 19 originally, as suggested when giving the motor and make of boat to the Marine Store in my area. I could not get over 3000 with that one. <br />Tried a 17 inch, and still could not go much over 3500. So, now I am on a 15, and I can not hit 4000. I do not know the entire history of the boat because I am the 3rd owner. Have had the boat tuned up. The drive worked on extensively. I am not sure what RPM's I should be getting in the first place.

 

[harrydohnert]

Re: WOT Question

I just found a chart on the Sea Ray website. According to their site, I should be using a 15 inch pitch prop, and my WOT should be 4600. So, I am too low.

 

[Haut Medoc]

Re: WOT Question

You said that they did extensive work to the drive? Did they replace the gears in the upper? With what ratio?

 

[Haut Medoc]

Re: WOT Question

4200-4600 rpm's is right.

 

[harrydohnert]

Re: WOT Question

I believe they changed one of the gears. I would have to find out what ratio. What should it be?

 

[Haut Medoc]

Re: WOT Question

I'm not an expert on this but, the ratio should be 1:50 to 1. The only way to know what you have for sure is to take the top off the drive and count the teeth on the gears themselves. Should be 22/20 I think. What did the invoice say?

 

[QC]

Re: WOT Question

You have to verify the tach. Simplest part of the equation. Sounds like it is right though. You are very close to the correct RPM. Gear Ratio is a possible cause and the shop that did the work should be able to help with that. The prop that was on there could have been tweaked slightly on purpose, so you are right to question what it once was. Does the guy at work know anything about it?<br /><br />Yes, Sea Ray may have noted 4600, but that could have been with no gear, one operator, little fuel etc. This could simply be about load, lots of stuff, full fuel, 12 passengers. When you check your WOT RPM are you trimming the drive out to get the most out of her? Smooth water? Bimini down? All of these things add load and decrease your WOT RPM. For example if it is near empty and all other factors are optimum, you may get the 4600, but with an extreme load, bimini up etc. etc. 4200. This would be an almost perfect (and unlikely) propeller compromise. If you find all else is correct and are still a couple of hundred RPM off, then you can have a prop shop take an inch out instead of going to the next propeller pitch. I am not saying that this is not an engine or mechanical issue. Just that there are multiple factors and any one can cause changes in the WOT RPM.<br /><br />Good luck!! We all go through this. I am trying different props now with mine too . . .

 

[jeff13601]

Re: WOT Question

Are you sure you are only supposed to have a 15 pitch prop? That sounds awfully small for a v8 on a 23 ft boat. What are both numbers on the prop. As an example mine is a 14 x 19 on a 120 mercruiser