WOT QUESTION (120 mercruiser)

[philtheskipper]

I just put a new prop on and my WOT dropped from 4300 to 4000. The new prop is the exact same as the old one, except for the wear the old one had(missing paint,pitts,etc.). Is this because the new prop is a little more efficient? Is 4000rpm ok for WOT on a 120 mercruiser? Thanks for your time.

 

[12Footer]

Re: WOT QUESTION (120 mercruiser)

Yes,Phil. It is probably due to a more efficiant prop. You probably have noticed a slight increase in speed too.<br />I had a Penn Yann that wound-out to 4800 routinely on my trip out to the reefs I liked to fish. I know I was under-propped, but didn't have the 450buks they wanted for a new prop $$$$$, ca-ching.<br />So I ran it like that.It ate impellers and fuel, but I couldn't kill it, even after repeated overheatings. And it got so hot one time, it MELTED the riser gaskets!

 

[fone_man]

Re: WOT QUESTION (120 mercruiser)

You should be 4200-4600 @ WOT... what pitch are you running & what kind of prop... SS or Alum... Hey its great we got 120 but still not enough info...<br /><br />Send it on............<br /><br /><br /><br />------------------<br />"Keep it between the Bouys & Good Luck"<br /><br />fone_man

 

[philtheskipper]

Re: WOT QUESTION (120 mercruiser)

It's a 1979 mercruiser 120, serial #5474115. I have a manuel and believe it says 3900-4300 WOT. The 120 Alpha/MR is 4200-4600. Is mine a Alpha/MR? I don't think so but could be wrong. The prop is 15 1/2 dia. and 18 pitch. ON 17' Steury which is very heavy for it's size. Thanks for input. Is that you fone_man? Change your username? You've been a big help guiding me through my problems. GOT TOWED IN TODAY AGAIN!!!! But that problem will be a new post once I cool down a little bit. What a money pit!!!!

 

[philtheskipper]

Re: WOT QUESTION (120 mercruiser)

Sorry, it's alum. prop.

 

[BRG25]

Re: WOT QUESTION (120 mercruiser)

I have a 14.5 x 19 on my 1994 Starcarft with 3.0 Mercruiser 135 hp. I get just about rated WOT of 4400 if trimmed correctly which I rarly do. Of course all boats are different and yours is probably a bit heavier. My oppinion is that if you get on plane fairly easily and are not under propped, don't worry about it. You're not going to win any races with this engine

 

[fone_man]

Re: WOT QUESTION (120 mercruiser)

philtheskipper:<br /><br />Yea... it is the "fone_man"... iboats board went down when one of thier programers was doing something the other night... shut the whole darn thing down... I can't get in under old user name & had a guy screaming for help on Friday & couldn't get to him... just went in and set up new one until followup call to iboats on Monday to find out "FIX"!!!<br /><br />When you say same as old one... same pitch 18??? Specs I gave were out of 86-96 Clymers Merc... shouldn't be much of a difference between the two but I will have to get another manual for older Mercs... know of any at garage sales??? I have been looking but nothing but self-help books on a positive attitudes... I will pick you one up & send it to you next time out... always remember " FiberGlass hole in the water, that you pour money into"!!! But boy aren't they fine when they are running good, nothing like it!!!!!!!!!! So keep a positive attitude on your boat buddy... & think "I wonder what the poor people out there are doing today???<br /><br />Has speed changed??? or is it the same??? I am full of questions tonight!!!<br /><br />Let me know as I was working on the Honda Friday night & Saturday morning... New Radiator... Runs fine all year long except between late June & Late September when Ambiant Tempature rises... & I run A/C but Honda said it always had a problem with Civic's in Mid 80's running warm... & I figured it out but that would be another BB not this one!!! But it is FIXED & that all that matters!!!! If it ain't the BOAT... It's the CAR or TRUCK!!!!! LOL<br /><br />Let me know......<br /><br />PS: I have to carry my brothers prop in to "The Prop Shop" tommorow & I will ask Laura, the owner, her thoughts on your issue... so let me know ASAP.<br /><br /><br /><br />------------------<br />"Keep it between the Bouys & Good Luck"<br /><br />fone_man

 

[philtheskipper]

Re: WOT QUESTION (120 mercruiser)

fone_man, I'm off to get some walleye with a buddy from work and I'm running late so I'll post more info later. Yea, the prop is same pitch, diameter, and type. Exact same prop, same manufacture, model, etc.

 

[fone_man]

Re: WOT QUESTION (120 mercruiser)

So my bro comes to town Friday... want me to go fishing... Can't you see I am working!!!!<br /><br />He rolls by yesterday morning to drop off his prop to have fixed @ "The Prop Shop" in Nashville... says I should have gone with him cause he could have got twice the limit on "Hybrids"... that tells you about my fishing skills... I always catch a "12 OZ'er" out of the cooler... "BUD"!!!! LOL<br /><br />Good luck & I hope you wear 'em out<br /><br />I will check with Laura this AM...<br /><br /><br /><br />------------------<br />"Keep it between the Bouys & Good Luck"<br /><br />fone_man

 

[philtheskipper]

Re: WOT QUESTION (120 mercruiser)

The speed is the same as well as take off power. I think it'll be alright. Well, as for the walleye I was going to catch this morning, DIDN"T HAPPEN!!! Just one and bunch of white bass which are useless to me. Oh well, better than being at work(off on Mondays). Just got back from my boat and found out that I have to run a new wire from my ignition switch to the starter, what fun. That was my other problem, at least it won't drain my wallet. Just wish I had thought to jump the starter yesterday instead of waiting for tow boat us to show up. Guess that's what those "buds" do to you. Well, thanks fone_man. Talk at you later.<br /><br />------------------

 

[fone_man]

Re: WOT QUESTION (120 mercruiser)

18 pitch.... never heard of it... hope it was a typo...<br /><br />Most are run this way 15, 17, 19, 21, 23... odd numbers!!!<br /><br />Spoke with Mike yesterday at "The Prop Shop"... you have old style prop "a monster", he calls 'em "Mouse Ears"...<br /><br />Might be worth a call to 615.255.0593 & discuss what you had & what you put on so he can get you on the right track.<br /><br />Have all info with you.<br /><br /><br /><br />------------------<br />"Keep It Between The Bouys" & "Good Luck"!!!<br /><br />fone_man

 

[philtheskipper]

Re: WOT QUESTION (120 mercruiser)

Thanks fone_man. <br /><br /><br />Yes, it is a "18" pitch. I know they don't make them anymore but I found it new in the box in a marine store with alot of dust on it. It was the exact same prop as the old one(mercury) so I picked it up figuring that the rpms and speed would be the same. Oh well, it'll do. Later.<br /><br />------------------<br />Phil