1993 Mercury Pro Max question

**Warrenroadie** · 12-20-2016, 05:59 AM

Looking at purchasing a bass boat with a 1993 Mercury Pro max EFI 150 hp. It has the thru prop lower unit, not the racing gear case. What is the difference between this motor and the same year EFI/XRI 150 hp motor? Cannot find much from my research over the past day, looking for expert knowledge from this group.

**tlwjkw** · 12-20-2016, 06:40 AM

mostly cosmetic stuff, exhaust divider, ecu... that gear case looks like it might be xr4/6?.. how many inlet holes on each side?

oh yeah... you'll be told '94 is first year of that motor!.. even with a late year ('93) build date...

**Warrenroadie** · 12-20-2016, 06:58 AM

So nothing that would make it less reliable as a fishing boat motor, right? Owner stated he purchased motor in 1993. Looks like there are 3 or maybe 4 inlet holes for pictures he sent last night. Older than me gentlemen purchased boat new in 1989, but I did not ask why he purchased another motor 4 years later. So gear case from xr4/6 would present no problems on this motor is what I thought too. I have owned both motors in the past. I just wanted input on what was the differences on Pro max efi versus normal efi/xri motor. Don't want to purchase a race motor for fishing, even though I do enjoy going fast.

**W2F a V-King** · 12-20-2016, 08:02 AM

I don't see why it would be a bad motor for your purpose..... It had worked fine since 1993 on that boat right? Regardless which lower unit it has, your not going to be running that motor way up high and surfacing the prop right?

It's going to be a fishing boat that you will occasionally run fast?

Guessing you asked him about any service work done on it? It is a great looking motor!

James

**Warrenroadie** · 12-20-2016, 08:07 AM

We discussed motor, but he never answered my question about recent service or maintenance work. He just stated it was great motor and issues with motor since purchase. I knew it would not be a bad motor, just wanted to know the main differences between pro max and regular efi. Thanks for taking time to comment.

**tlwjkw** · 12-20-2016, 08:12 AM

those are probably tha most dependable motors merc has built... tha "little" gear case is tha weakest of all, one ratio, limits hub size with "thru hub" props.. still my favorite ta modify for a hot rod.... will probably be jus fine ona fishin' boat...

**JCSmile** · 12-20-2016, 08:49 AM

If anything, I would argue the 150 promax is more reliable. As far as differences, the block for a 150 PM is the same as the xri, differences are a better fuel curve with a higher rev limiter, solid motor mounts, and you get the high performance cowling. We have one on an Allison and it runs hard. Has been 88mph. There may be some other minor differences, but the internals are pretty much the exact same so they are reliable with good fuel and plenty of cooling. Very easy to work on.

**JCSmile** · 12-20-2016, 08:50 AM

Also, these motors are known for being one of the strongest 150hp from the factory. Completely stock most of them put out in the 165hp range.

**Warrenroadie** · 12-20-2016, 08:52 AM

Great, that was what I was hoping to hear. Reliable, good performer, good cooling system and easy to service. I probably will not use the higher rev limiter, but solid mounts will be nice for handling.
Thanks again!

**JCSmile** · 12-20-2016, 09:01 AM

I would check compression, leak down if possible, replace the water pump if not serviced recently and check gear oil in the lower unit. Get yourself a service manual and go for it!

**Warrenroadie** · 12-20-2016, 09:07 AM

I was planning on checking compression, check gear oil integrity and ask about motor service when I go to look at boat. Who sells a good service manuals?

**Warrenroadie** · 12-20-2016, 09:16 AM

What is rpm limit setting on this motor?

**JCSmile** · 12-20-2016, 09:21 AM

I'm not sure if they are still available but I have always like the merc service manuals for the promax. Hopefully someone else will chime in if they have had a good experience with using another one.

**W2F a V-King** · 12-20-2016, 09:21 AM

BUY an OEM Mercury Manual...Nothing else..imo

Aftermarket shop manuals are usually copies in part from the OE manual, and lack a lot to be desired.
Shop for it...it may or not cost more, but well worth it.

Mercury Part number to search for... 90-824052R1 covers all 135 through 225 1992 up includes Promax 150/200/225. Serial numbers 0D082000 and up.

Found mine on eBay used in good shape for cheap.

James

**JCSmile** · 12-20-2016, 09:24 AM

The RPM setting is officially 6750. At this point the go into a rich fuel wall and the timing boxes retard timing. With small props you can hit the wall and go higher. Ours runs 7800 every time out with a 24 Yamaha, but we have yet to determine if the previous owner moved the rev limiter or not. I think the low port height runs out so 7800 is all they will spin.