1992 Mercury XR4

[Chris]

Ok guys,

Here is a question for you. I have a 1992 Mercury XR4 150 HP. What is the maximum RPM range for this motor. I had one dealer tell me it was 5000-5200 and another tell me it was up to 5400.

To be safe I've been keeping it around 5200 RPM.

Any ideas?

[Chris]

Ok guys,

Here is a question for you. I have a 1992 Mercury XR4 150 HP. What is the maximum RPM range for this motor. I had one dealer tell me it was 5000-5200 and another tell me it was up to 5400.

To be safe I've been keeping it around 5200 RPM.

Any ideas?

[JW]

In late 1991 for the 1992 model year, Mercury introduced the XR6. Are you sure you don't have a 91 or earlier? The XR6 introduced the 2.5 150 to the line-up, replacing the 2.4 XR4 150. I do not know for sure, but your factory recommended rpm range should be the same as mine was, 5400 - 5800.
To find out what motor you actually have, put the serial number on the Mercury Parts Express section of the Mercury site and it'll tell you what motor you have. That's what I did to make sure my '95 Promax was indeed a '95 Promax. The site also told me I have the Torqumaster lower unit with 1.87:1 gearing.

1995 2100BR/1995 225 Promax/23" Tempest

[Chris]

JW...

As soon as I get it out of storage, that's exactly what I'll do. /infopop/emoticons/icon_smile.gif

[JW]

Here's our oldest 'Ask the Experts' post! I think it's time Chris put some hot rod money into that XR4/Pulse 170!

[jrumon]

Chris... Did you ever do anything to this motor or find out if it was a 2.4L or 2.5L???

Those 150's are the EASIEST motors to WAKE-UP!!! You can get 200 HP out of them for under $1000 and maintain ALL FACTORY RELIABILITY!!!

Imagine how much more fun your 'Mate would be with 25% more power! http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/biggthumpup.gif Jim.

[Drex]

Jim,

I have a 2001 XR-6. How can I get a reliable (I don’t want to be wrenching on it all the time) 200 horses out of it for less than $1000?

[jrumon]

Drex... your 150 is a "DETUNED" or "CHOKED" version of a 175 or 200. The way Merc gets the various power ranges 150-175-200 is all in the "bolt-on's". The block, crank, rods, pistons, and heads are the SAME...

Think of it as this... Merc PREVENTS it from making more than 150hp by RESTRICTING the air going in and the air going out!

Your 150 has 5 factors to limit power...(in MOST CASES).
#1. Restrictive exhaust tuner...
#2. Reed stops or smaller reed cage assemblies...
#3. Restrictive carb air box assembly...
#4. Smaller carbs (sometimes)...
#5. Engine timing specs (sometimes)...

If you change over to those parts listed above to those from a similar year 200, you will basically have a 200! No change to FACTORY reliability or durability!!! Straight forward, no voo-doo, and easy to do!

[JW]

I think the 200 block has higher porting than the 150's. That's one of the bigger differences.........

[Chris]

It turns out it's a '91 fellas.

[jkeiper]

Drex;

Actually the 150XR6 block is not quite the same as a 175 or 200. The porting and exhaust chest is different. While you can "bolt on" good power, you might be hard pressed to make 200hp without some porting.


Jim


Coming soon to a lake near you! <span class="ev_code_RED">"Secret Agent"</span>

[jrumon]

WOOPS&gt;&gt;&gt; I got lost in this one...

Sorry Drex, but just READ your post and didn't realize yours is a 2001 motor http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/brickwall.gif... so I'll shut up because I haven't been in one that new yet (although the same principals should apply)!

I have been in a several 2.0L 150's, 2.4L 150's, But not a 2.5L 150...(2.5L 175's, 200's, and 245's YES)... Of all the 150's I played with, I never noticed any difference with porting??? In fact, I ordered a merc service replacement shortblock and the SAME part number was listed for all 3 power levels 150-175-200...&gt;&gt;&gt;NO DIFFERENCE&lt;&lt;&lt;!

Now you guys have me currious as to if and when merc started messing with ports... TIME FOR SOME RESEARCH...... TO BE COMTINUED..... http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/thumb.gif

[jrumon]

Chris...

I forgot to ask you...
is your '91 150hp motor a "2.4L-XR4" or "2.5L-XR6"...?

[jkeiper]

jrumon;

Yeah, Merc. changed porting between the 150 and the 175 block. The 175 and 200 have the same porting. Also the exhaust chest is slightly smaller. They did this in 1999+ when they started to use the same block as the Opti. I don't think the 150 has the boost ports either. The reman power heads are the same a lot of times just so it is more of a "one part fits all" type thing. Hope this helps.

Jim

[jrumon]

jkeiper...
just to clairfy... Merc did that ONLY to the newer 150's starting in 1999-up??? I can see it making sense on the opti's because of fine tuning the power level and maximizing fuel economy... http://www.checkmate-boats.com/infopop/emoticons/icon_rolleyes.gif I can also understand why they would carry over that block to the carb and std efi models because the technology is there. http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/Eyecrazy.gif

The "old-school" days of producing one block and "adjusting power output" by external factors is looking like a thing of the past! http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/brickwall.gif

OK all you hot boaters... start stocking up on those older Carb 2.5's and 2.4's... at least you have room to IMPROVE on!!! http://www.checkmate-boats.com/infopop/emoticons/icon_biggrin.gif

[jkeiper]

At least without EFI you don't have the Motorola ECU on that XR6. The Motorola ECU makes it a little harder to play with the timing and rev. limiter. I still haven't got the limiter on mine raised.

Jim



Coming soon to a lake near you! <span class="ev_code_RED">"secret Agent"</span> http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/devil.gif

[Chris]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by jrumon:
Chris...

I forgot to ask you...
is your '91 150hp motor a "2.4L-XR4" or "2.5L-XR6"...? <HR></BLOCKQUOTE>It's a '91 2.4 XR4

[jrumon]

Chris, your motor can be "upgraded" easily for more power, but if your motor has the smaller inline six style lower that the XR4 used, you might stress it beyond it's capacity if not careful! http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/brickwall.gif

[addgasgofast]

Small gear case used on the xr6 motors. I think that the xr4 motor was basiclly a carb 175hp with 150hp decals on it so it could be used on tourney fishing boats with 150hp max rules. The ruse didn't last long nore did the production of the xr4.

[JW]

I'd like to find one for my project boat.......

[Chris E]

Correct me if i'm wrong, but i had heard that the XR4 engine was a lot closer to 172hp because of the bass boats it was installed for - also has a different gear ratio 2:1? instead of the standard ratio.

[JW]

I'm no expert on the XR4, but I do know the XR6. It's gear ratio (if you ordered the 'XR6' gear case) was 1.78:1

You could also order it with the standard larger case 1.87:1

I always thought the XR4 also used the smaller case at 1.78:1

[jkeiper]

JW is correct! The stock XR4 had the small hub gear case and 1.78:1 gears. Lots of people changed to the large hub case after the orignal blew apart. The small hub case has it's place and can be built to be fairly strong. They were great on light weight hulls. There are a lot of people that have never had a problem with them. My dad has an XR4 on his 19.5 Lund Tyee and just shucked the gear case last year. 15 years on a HEAVY boat is pretty good. I had one on a bass boat that made it a good 10 years before it blew. Like anything else some go a long time some don't.

Jim