1980 175 Merc info please

[KonaKustoms]

I have a 18' champion tunnel-hull bass boat I got this week and it was runnin crapy so I did a compression check and looked it over to find the problem. Ok here is the deal- It lost the top side of #2 piston but the block looks good just alot of alum. from the bad piston. Im really not shure I want to keep this motor but it is the original motor from when this rare boat was new so do you think it will hold together if I just clean the cyl. up and throw a cheap piston in it and new rings to see if I want to keep it? I think it is a 2.0 L engine from my research. I have never had a small motor like this so how do they run?
Motor is a 1980 V175 model V-6 20" Shaft, inboard trim pump motor. ser#570****. Thanks in advance for any advise on a cheap rebuild to just to get it runnin if it will even push this hull.

[KonaKustoms]

anyone ever run one on a heavy tunnel-hull?

[Raceman]

For an informed opinion on fixin' the cyl in the way you described you'd have to shoot some GOOD pictures and post 'em. In any case, you can bore 1 cyl and just do 1 oversized piston if the rest are okay, rather than having to do 'em all.

A lot of people have run the old 2 liter 1750's on heavy boats. Remember....... in 1976 & 1977 they were as good as it gets.

[Capt.Insane-o]

Good motors and tough as nails. It'll push that boat fine, prop it for around 6200 with a light load. It's not going to be a super speedster but it'll get along.

[KonaKustoms]

OK thanks, I will post some pics of the cyl., I was always told not to put just 1 oversize piston in a merc it would shake itself apart, have u done this before? I always just do them all on the 3 motors I have rebuilt. I just want to see how it runs without ruining the motor.
Thanks again for the reply's guys!

[Raceman]

OK thanks, I will post some pics of the cyl., I was always told not to put just 1 oversize piston in a merc it would shake itself apart, have u done this before? I always just do them all on the 3 motors I have rebuilt. I just want to see how it runs without ruining the motor.
Thanks again for the reply's guys!

There's NO PROBLEM with just doing one on a Merc. There are TONS of 'em running around that way. No more shaking with one or two oversized ones than with a full set.

[KonaKustoms]

Ok sounds good, I will tear it apart this weekend and see how the rest looks.

[KonaKustoms]

Here are a couple pic's, it has 118 to 120 psi on all other cyl.
It actually fired up and ran like this with 0 psi comp.-WOW

[Capt.Insane-o]

Probably have to be bored.. and you'll need a head. I'm sure I have a few about if you need one. The "shaking itself" apart is a complete and utter myth in any engine.

[KonaKustoms]

ok, A good lifelong friend of mine and his father own Nameoki Village Marine in Granit City, Ill. and he has a head with the same exact casting number but if it is not rite I will call ya ok.
I have built a few Yamaha 250 race motors for my STV tunnel-hull But im not a Merc. guy so all info is greatly taken! In my opinion they are all good motors if a guy takes care of them and services them rite and any of them can run with the rite parts and machine work but im a yamaha guy not a merc. guy so thanks again for the info sir!

[phil blomquist]

i ran the exact motoron my valero yt capt insano is right on the money 6200 great solid motors run forever easy rebuildable lots of parts on the market good luck:D

[KonaKustoms]

Ok sounds good, we are gonna try to keep this rare boat all original and hope it will run good, I have my doubts, but it's just a bore job and piston and gaskets so what do we have to loose to learn a lesson here.....lol
Thanks again guys and 6200 wont pop it huh? I have never had anything this old!!

[Capt.Insane-o]

Ok sounds good, we are gonna try to keep this rare boat all original and hope it will run good, I have my doubts, but it's just a bore job and piston and gaskets so what do we have to loose to learn a lesson here.....lol
Thanks again guys and 6200 wont pop it huh? I have never had anything this old!!

I still have one from 1976 with the original 3 ring pistons. I turned that motor 72-7300 for miles and miles and miles and miles and miles and miles. Still ran perfect when I took it off and stashed it away. I would up the jets a couple sizes due to gas quality though.

[fyremanbil]

If you have it apart, you can easily do a few mild mods and improve the performance. I have run the Mercs in endurance racing and never had a failure caused by reasonable RPM limits. The merc cast pistons will run continuously at 7500 RPM until the rings wear out.

[KonaKustoms]

Ok here is the deal, Im a Yamaha guy, I have built a couple merc.'s but not this old, heck I was 10 yrs. old when this thing was built. After extensive research on the Champion Tunnel-hull bass boat and finding out forshure it is one of less than 20 ever made by Champion before production stoped in Arkansas. This is the original motor that was on it the day it was sold new and was sold 5 miles from my home now!- WOW what are the odds on that? Anyway we are going to do a complete cap-off restoration on it and this motor is staying so if there is any perf. mods that wont trash the powerhead on long runs im open for sugestions on this old thing! Port work? carb work? heads shaved? ect. ect.
So what do ya guys think I should do to it? Im thinkin it can make 200 HP or better if built rite?

[KonaKustoms]

I was told by a good friend (nucklehead merc guy....lmao) that i need to raise jet size by 2 and retard timing by 2 deg. for shure and tune from there.

[KonaKustoms]

Also he said change the rod bolts for some reason they mite fail, whats up with this?

[wrechin2]

I have a set off heads off a 76 175 in the misc parts if you end up needing a set.

Good luck finding a set of bolts if you have the 5250 rods. They are different than the 8118 bottom guided rods.

http://forums.screamandfly.com/forums/showthread.php?t=203191

[Dave S]

The old Merc Rebuild Phazzze...... Just clean the rod bolts and Loctite them. Times 10 uses.:eek: You can Re use the streach bolts ONCE.:eek: But I have done more.:rolleyes:5250 rods are good but have small contact area at the rod break and need carefull fit when bolting. I tap the bolt to set the rod.:p

[fyremanbil]

There's lots of info on here about mods for them. 200hp is about the practical limit without using race gas or adding finger ports or tubes. A good model to follow is to copy the SST120 spec, or maybe a bit lower on port height to start with.