WOT RPM for 4.3L Mercruiser

[EZDude]

Hello to all,
This is my first post in this forum, so please be kind

I am trying to replace my recently damaged propeller and need some information to do so. I am trying to find the WOT RPM for my boat.

I have been reading these forums quite a bit lately and have found a ton of good information. Unfortunately, I haven't found an answer to my question.

We put a new engine in our 1990 Glastron Sierra 175 recently. The engine is bigger than the original. This engine is listed as a 4.3LX V6 Mercruiser. It is a 4 bbl with Vortex heads. From conversations with the dealer, it is a 220hp engine, although I have not actually found a data sheet on this engine to confirm this. Also, it has the Alpha One sterndrive.

My questions is...

What is or where can I find the WOT RPM for this engine on this boat?

Thanks in advance for any advice or feedback.

 

[extreme76]

Re: WOT RPM for 4.3L Mercruiser

4400-4800 rpm

 

[EZDude]

Re: WOT RPM for 4.3L Mercruiser

Any other takers out there?

Is there a website that would have this information?

Thanks.

 

[extreme76]

Re: WOT RPM for 4.3L Mercruiser

Depending on the year it would be in Service Manual 18 or 25, which unfortunately are no longer available online.
-
However, I have them both and it is 4400-4800 rpm

 

[paultjohnson]

Re: WOT RPM for 4.3L Mercruiser

I concure with EXTREME 76 WOT 4400-4800 is what it says on decal on my 86 4.3

 

[Kaplooi]

Re: WOT RPM for 4.3L Mercruiser

Is the outdrive original or did you change that with the engine too? If it's original and you had a 3.0 4 cylinder before you should change out your upper gear set to either 1.81:1 or 1.65:1 with a 4.3. Some people simply re-prop to make up the difference but this puts an undue amount of strain on the drive gears and invites fatigue related failures which can be of the explosively catastrophic variety if consistently run hard.

Ultimately your SN is the most reliable way to look up exact HP figures but I believe 96 and new Vortec motors were all given HP ratings at the prop shaft as opposed to the old specs that rated HP at the flywheel, so your motor is probably rated as either a 190 or 205HP 4.3LX but probably generates around 210-220HP at the flywheel.

 

[EZDude]

Re: WOT RPM for 4.3L Mercruiser

@Extreme76 - Thanks for the info. I really appreciate it.

@Kaplooi - The boat originally had a 4.3L of the 170HP variety. I kept the original outdrive based on the mechanic that put in the new motor recommendation.