Got her fixed (the engine that is)

[VA Chris]

Well I got my boat back from the shop (Bowers Marine in Hagerstown MD) I like those guys especially Scott the engine tech.



Apparently the source of my unknown engine cutouts and missing was a bad "rev limiter" spiking voltage screwing things up. Runs great now but something Scott brought up has me a bit confused. He said I am over propped running a 21p getting 5000 rpm WOT and that he would like to see me getting 5500. When I told him the manual said 5250 was the recommended top end for this motor he said he new that but that in his opinion and experience base I am better off getting the 5500 he stated and my motor would last forever by doing so. He said to drop down to a 19p. Any thoughts on this?

 

[TOMMY RICH]

do they make a 20 pitch?

 

[Jim B]

Maybe Pat can chime in and confirm this but i have heard the 115 and 125 mercs dont like to be overrevved one bit. From what i have heard they have a tendacy to blow up if you do.



Its not like the v6 models that you can run over the limit.

 

[TOMMY RICH]

Could hit the rev limiter if it's over on RPM

 

[Jim in VA]

Chris - how MUCH do you trust this guy? Enough that you're willing to bet on having to buy a replacement engine (or power unit) if he's wrong? Sure, he has experience, but does his anecdotal evidence compare with millions of dollars or R&D spent by Mercury? Something else that would give me pause - don't know if it applies to your engine or not, but there are now stickers on the new Mercury engines that warn users of a "black box" in the engine. The box basically monitors engine operation and can tell whether proper oil has been used, break-in procedures have been followed, and engine use has not been outside manufacturer recommended specs. The sticker goes on to warn users that any failure to follow Mercury-specificed operating parameters can cause the warranty on the engine to be voided. Saw these for the first time on the engines of the new boats for sale at Bass Pro in Maryland.

 

[TOMMY RICH]

See if you can find someone with a 20 to try...most will and hope you get er' where you want her.

My max on my 90 is 5500 and I feel very comfortable @ WOT and 5400 RPM's.

 

[Jim in VA]

Hey Chris:



Sorry about my original post. I reread it and it sounded a lot snottier than I intended. It wasn't meant that way at all. I guess I was trying to say that (IMHO), your best bet is to stick with what the manufacturer recommends. Afterall, they designed and tested the engine. I would imagine if the manufacturer could get more oomph out of their engine by telling customers to run a higher RPM, they certainly would. It would be a great selling point. But if they say the limit is X, then there's probably a pretty good reason for it.



Good luck!

 

[TrepMan]

VA Chris - I won't jump in on ythe 5250 vs 5500 rpms, but mine is the same motor and I will not look for a way to get it over 5250rpms that just me.



but, if you go looking for different props, make sure you know what you have and what you are getting. For instance, a 21p 13inch diameter prop and dropping to a 20p 13 1/4 inch prop of a different brand will not give you the 200rpms you need. Speaking from experience, I bought a prop off ebay the owner said was a 13 inch diameter, got it in the mail and its a 13 3/4, even though it was 1 pitch lower then my current prop, my RPMs went Down not UP. Now I did raise the motor on the jackplate and got the RPMS up with the new larger diameter prop, and so far its running great.



Just something to think about, if you have say a laser II 21p, then i'd say you want a laser II 20p.



Trep

 

[Bruce Freeman]

Chris, I have a 20P stainless prop as my spare if you want to try one? Before anybody shoots me, please remember I know a lot more about cars than boats. The manufacture will always put a low number up to save us from ourself. Because I know that if I am told 5000 is max I am looking for 5200 or 5300. It's the nature of the male beast. I was told when I bought my Champion with the a 2004 150 XR6 that even though the book says 5800, to twist it to 6200 and it would like it. The 60 Mecr on the Tracker I had was rated at 5400 but it ran best around 5800. NOW with that said how accurate is the tach on the dash? + or - on most marine gauges seems to be far from correct. So if it has a rev limiter you can bet even that is well below the max rpm. Just my .02

Let me know if you want to try the prop.

BF