Hello. First time poster. Mercury Black max 175 questions

[1blueheron]

Hi, This is my first post. Some guys over at THT suggested I post questions over here on my Black Max 175 Merc. Reportedly this is the home of the experts?


A little about me. I am in the process of building a 25' Plywood and epoxy skiff. Plans are based off the Great Alaskan/Tolman Skiff.

It should weigh in at about 2000lb when completed and outfitted and has 12degrees deadrise at the transom.

The shell of the hull is complete and I am now working on completing the inside and getting all the rigging in place.

I bought a boat that had a 175 Mercury Black Max on it to use as my initial power plant. The motor ran but the transom was rotted out so I gave my buddy 300.00 for it. the only thing I know needs done to the motor is the tilt/trim unit needs replaced. I have a 150 merc donor that I have pulled the tilt/trim unit off that I believe will swap over.

I think the weight/HP ratio is about right for my boat.



So my question is, is the 175 worth putting time and money in and can it be made to be reliable and where should I start on going over this motor and making sure everything is in order.

The previous owner deleted the VRO and was mixing oil in the tank at 50:1.

Thanks

[Aaronhl]

Yes, the 175hp is worth putting money into it...I would say other than it not being a 200+hp, it's a highly desired 2.5L non-race style Mercury outboard. I would say keep what you have because as long as the compression is good, that motor should run for a long time well taken care of...lucky you have a 150 and 175 because most of the parts should interchange as long as they are around the same year.

That 175hp engine is a 25" XL and you skiff is a shallow boat, so you will probably need to covert that engine to a 20" L and mount it high on the transom. Will take some effort to shorten the shaft. Let me know if you dont wanna do that I could take that engine of you hands LOL

As far as what to check, the engine was running, but still start with the compression make sure it's around 120 psi in each cylinder with a good guage, if not you have some internal work to do. If compression is good you might be ok to start try to start it. Without knowing the history of the engine there could be a lot of stuff you gotta do like cleaning carbs, checking reeds, lower unit water pump/impeller and gear oil, etc. Of course you could replace all the parts you want on the engine like new stator but you may not need to, get it running with the general maintenance I mentioned ad you should be good to go

[Merc 2.5]

I agree with aaron. Check compression, go thru fuel , prob replace fuel lines also , and along with water pump do poppet valve and stats

[1blueheron]

Thanks for feedback. Did a compression check this AM. All Cylinders are pretty even and read 100psi on my gauge. A little low. Could use a gauge with smaller gradations. Suspect my gauge may be off a bit. Going to pick up some fresh gas today and see if it will fire up ok. Sounds good turning over.

The boat plans call for a 25" shaft motor so I should be good there. It has quite a bit of freeboard.

Would like to get a hard copy maintenance manual. Which one is best and which one covers the model I have.

[Aaronhl]

Post pictures of your boat I am sure everyone would like to see it

[1blueheron]

Post pictures of your boat I am sure everyone would like to see it

Here is a few pics from various stages of the build. Forgive some of them are wrong orientation. Still trying to work out the quirks of posting pics.

[FUJIMO]

...thats one hull of a boat...

[1blueheron]

Cowl on the 175 needs a front latch. One on it is completely shot.

[tlwjkw]

justa a little info.. might wanna do some diggin' on tha motor... mercury marine website:

if serial number is what it looks like.. 0G303694 = Service Literature for MERCURY 2.0L 135 XL

but thats # on tha clamp so powerhead could've been changed???

[roadkill636]

Yep. 1996 Mariner 135 HP

[1blueheron]

So is there a way to correctly identify the powerhead? I was going strictly on the cowl labels and the serial number had me stumped as well as there is nothing even close listed for a 2.5L 175. Perhaps someone swapped the clamp in a previous life? Does a 175 cowl fit on a 135?

[tlwjkw]

physically they all look/measure/mount same..

look on top of block behind tha flywheel you will see a "welsh plug.. looks like a freeze plug.. it may or may not have tha serial number stamped in it.. look on port side by tha throttle/timing arm where tha block splits.. might be stamped on tha "block half" side.. you can start there.. if its still in question someone can give a few "other things ta look for.. if possible get some pictures of tha powerhead.. front, both sides, back... close-up of port side of carbs.

[1blueheron]

Perhaps this will help.

Casting numbers on heads are 18488-C4.

Number stamped on freeze plug is 0G245578. When I plug that into serial number decoder it comes up with

MERCURY

1995

175

1175422RD

The 1995 175 seems congruent with the period of time previous owner bought the boat. Suspect it is correct and the serial on the clamp is bogus.

[tlwjkw]

you're absolutely right.... block # always overrides clamp #.

0G245578 = Service Literature for MERCURY 175 XL

[Aaronhl]

Will you be able to get that ship in a bottle out of the garage??