Max IV Engine Swap Specs

[Swamp_thing]

I have a 1996 Max IV with an 18 HP OHV Vanguard. Recently the engine knocked a round hold in the back side of the block/ cast casing.

I saw several posts on engines but couldn't find if there are other things I need to consider when purchasing a replacement engine.

How hard would it be to replace the block / main casing vs buying a new engine? Is it worth the time / trouble considering it is already an old engine?
If I go to a 23 HP Briggs, is there a certain one you all recommend? Are there horizontal shaft engines that will not work even though they have the correct shaft? I saw this one for sale on eBay for $600 but didn't know if this mower engine would bolt up correctly with the correct height making the belt tension right.

BRIGGS & STRATTON 25HP OHV V-TWIN RIDING MOWER ENGINE NEW WITH BRIGGS WARRANTY

I understand I need a 1" keyed shaft, are there a lot of differences on the height from the base of the casing to the shaft that would impact belt distance? Am I going to need to build a spacer / bracket if I go with something other than the original?

Sorry for so many questions, just ready to get it running again and not sure what all I will need to consider when buying a new motor that isn't directly from RI.

Thanks in advance for any / all help! It will be greatly appreciated!

[amphibious drew]

When buying a replacement Briggs for your machine, you would reuse the governor spring, clutch, throttle, and choke cable from your original setup. It is a bolt in mod no matter which model 23 with a 1" horizontal shaft engine you buy. You may need to adjust your carb to your preference, but the blocks are all the same. The one option I would avoid unless its a good deal is the gas tank air box. The standard air filter cover is what fits under the machines stock engine hood. I used an engine that came with the gas tank on an Attex and just used a bucked for an air box, but the factory setup is a bit better looking.

[Swamp_thing]

Thank you Drew, that is a huge help! To be sure I understand correctly and don't mess up an order, the distance from the shaft to the bottom of the engine that mounts to the engine platform should be the same regardless of which 23 hp I use as long as it is a 1" keyed (non tapered) shaft. Will that engine shaft height be the same as the current 18HP I have as well?

Great to know on the air filter cover. If I put a rack on the back and don't reuse the engine cover, are there any other draw backs to the gas tank air box?

Thanks again for your help!!!

[amphibious drew]

Correct on the shaft distance, and no on the airbox. Like I said I have a bucket, and I believe another member uses a brownie pan. As long as it works and your comfortable with it.

[Swamp_thing]

Thank you Amphibious! I will see what I can come up with. Is there a place people have found here that the recommend for buying a motor? Do you know of anyone with a used one for sale on 6x6World? I looked and didn't see one.

Thank you again for all your help, I feel better now about what I am looking for.

[amphibious drew]

I have purchased 2 engines on eBay both were basically new and a great price as well. You have to be diligent and search regularly to find the best deals. I have bought a few used engines off Craigslist, but the really good deals go fast, and I have know people to get a giant paperweight for a really not so great price considering what the got. I have also had great luck buying engines off other forum members, however, I don't remover anyone ever selling a 23hp vanguard on the site. The people who get them, like them.

[Swamp_thing]

Thanks, what are your thoughts on going back with another 18HP in a Max IV? From what I've seen it sounds like the biggest gain I will see is the torque from a 23hp.

I don't drive wide open often so top end isn't a big influence on my decision. Where will I actually feel the gain from upgrading to a 23hp? Is it smoother acceleration, lower RPM to start driving from a stand still? Do you think I would be better off sticking with an 18hp so i have my old engine as backup parts?

Man, I'm going to owe you a beverage (or several) of choice for all your help!

[amphibious drew]

I just put the 23 in my Max IV and I love it. I creep up hills loaded up with people and have not even come close to running out of power at all. You feel it down low, which is where you want it. The top end really isn't effected at all by hp. Your engine rpm, clutching, and gearing do. If you got enough power to get you there is a different story. As for the 18, it gets the job done in a Max IV....but you could always sell off the extra parts because the 23 is a monster. It's really your decision.

[Swamp_thing]

Thanks again Amphibious! I know this isn't the correct thread for this question so my apologies in advance. I don't have a lot of experience with these machines and noticed I can feel some flexing (more like twisting) of the body / floor when driving it. Is that normal or is there possibly something else I should be looking for? The frame isn't rusted, broken, or cracked and the machine overall appears to be in great shape. Just wanted to be sure I'm not missing something else before buying another motor.

[amphibious drew]

Frame flex is normal.

[Swamp_thing]

Amphibious, I can't thank you enough for all your help. Hopefully I will be able to reciprocate in the future. I picked up a Honda 20.8 Net HP yesterday. I looks like it will have a little more torque than the 23hp Briggs and was actually a little cheaper (just hope it holds up as well). Wish I could have found a used engine but I'm afraid it would take too long to get it back running.

If anyone needs any parts for a Briggs Vanguard OHV V-Twin 18hp, I have them. I just put on a new stator before she blew.

Thanks again!

[amphibious drew]

Should be a good choice of engine. You may want to post your old engine/parts for sale in the "for sale" section of the forum. As for helping out, don't mention it. Not too long ago, I knew nothing of how these machines were built or even function mechanically. I always enjoyed tinkering here or there, but never had much experience. I am actually just a marketing guy. The people here taught me almost everything I know about the hobby and small engines. Some of the guys still post a lot on here, and others post less and less, but when they do, it's usually very insightful. I have had my hands on more than a few machines since I have been involved, and I always learn something every time I work on one, but the truth is, if it were not for members like JpSwift, Hydromike, RDR, Don, Lewis, George, Freq42, Racerone3, George, jerseybigfoot, and so many others that have me advice and lent a hand while I battled with my tomahawk to make it run right and built my racer out of garbage, I probably would have given up on the hobby. So I guess we should really thank admin Mike for giving us a way to help each other out.

[Swamp_thing]

Thanks again Amphibious, I will definitely do what I can to help in the future. I am still learning but it is a fun trip getting there. The engine arrived this week while I was out of town so I started installing it last night. Hopefully it will be back up and running by tonight.

Many Many Thanks for helping someone who knows very little!!!