Pistons on Ford 302 / Mercruiser 188

[kenny nunez]

Actually your and all automotive engines are left hand rotation when viewed from the flywheel end which is standard rotation. Quite often single engine straight drive boats are right rotation. It can really get confusing especially if the starters are rear entry, as on jet boats and straight inboards.
OMC and Volvo did have 170 hp engines while Mercruiser only had 188s.
Mercruiser used 2 barrel Holleys on the 188s. As I stated before your engine should work out as long as you have the correct carburetor. From what I can see it has a Ford automatic transmission kick down lever so it is a automotive carburetor.
Sierra Marine #18-7635 is a 300 cfm that they show as a rebuilt.
Also Sierra # 18-7636 is a 500cfm model. You may have to also pay a core charge. Sierra only shows these carburetors that I posted for the OMC engine. For some reason they do not show any Holley 2 barrels for Mercruiser.
There are several places on the internet that specialize in rebuilt marine carburetors.

 

[flashback]

Never saw the movie. That is the original color Burgundy, just the cross ref number PPG gave me when I painted it back in 1992 is a touch more red, actually like it better.

Rust wasn't too bad on this but accident damage was and the engine trans and diff had been blown up at various times. I found out after I had bought it that it was originally tripower and 4 spd. I just got the tripower back on it in 2021

Hopefully you got the 4 speed too!

 

[IslandExplorer]

I don't think prior to the Q-jet coming out they had a 4 bbl big enough in an OEM format.

The AFB that was on the early 4 bbl engines is 500 cfm. I don't think the 3x2 had better mixing than the 4's. I think in the end there is a reason that Pontiac went to a higher rise intake and the q jet. The factory 67 and up intake is hard to beat.

A lot of guys have really good results with tripower and other guys have good results with a 4 bbl so I dont think one is better than the other. the tripower essentially functions like a 4 bbl as the end carbs only kick in at about 75% open throttle. End carbs dont have choke, idle, or power circuits so they are essentially the secondary's on a 4 bbl.

Where a tripower on a 64-66 GTO does excel is looks, resale value and noise when WOT. Nothing sounds quite the same as a poncho and tripower.

Unfortunately the Pontiac rods didn't like it much past 5200 so most of them didnt make it through the 70's. I bought mine in Jan 1990 and it had been off the road since 78 or 79... and by then engine was gone, trans gone, diff was previously exploded. Either the guy I bought it off of or the guy he bought it from had two 65 gtos. the front end was off a different (color) 65 GTO and the engine was cast 6 months after my car was built, so its hard to piece them back together.

I kept a wide ratio 4 spd Muncie in it. I bought it from a classified add back in the day and rebuilt it. Actually works very well.

PO had put 4.33's in my car. I got a 8.2" BOP rear out of a 66 cutlass ($45 at u pull it yard back in the day...) with 3.08 gears and a posi and swapped them in. Very nice on the highway but a little tame when you are on it. I think eventually I will go to a 3.36 or 3.55, would match my cam better

In the end I wanted to limit my mods to day 2 type stuff. I never really wanted a resto mod, and it has taken so long to actually get this streetable I am just happy I can drive it. Definitely appreciate it more than I would have when I was younger.

Well I learned something today, thanks for the explanation! I didn't realize that's how the throttle worked on those, that totally makes sense though and can imagine the sound must be totally worth it when those end carbs open up. Look, sound, and feel are far more important than just slip numbers in my book. And that is indeed a huge jump in the gearing, but luckily seems like you've got plenty of power available to muscle through anyway. The 4.33's probably would've been a lot of fun but also terrible on the highway and your poor rear tire's life expectancy!

 

[IslandExplorer]

Actually your and all automotive engines are left hand rotation when viewed from the flywheel end which is standard rotation. Quite often single engine straight drive boats are right rotation. It can really get confusing especially if the starters are rear entry, as on jet boats and straight inboards.
OMC and Volvo did have 170 hp engines while Mercruiser only had 188s.
Mercruiser used 2 barrel Holleys on the 188s. As I stated before your engine should work out as long as you have the correct carburetor. From what I can see it has a Ford automatic transmission kick down lever so it is a automotive carburetor.
Sierra Marine #18-7635 is a 300 cfm that they show as a rebuilt.
Also Sierra # 18-7636 is a 500cfm model. You may have to also pay a core charge. Sierra only shows these carburetors that I posted for the OMC engine. For some reason they do not show any Holley 2 barrels for Mercruiser.
There are several places on the internet that specialize in rebuilt marine carburetors.

Yeah, mine turns clockwise looking at idler pulley, counterclockwise from flywheel. I'll probably pull the carb over the winter to assess everything with it. And thanks for the part numbers! Wonder what the deal is with the 188hp rating.. Seems they usually round off 100+ HP numbers to nearest increment of 5 but guessing there was already a 185 and 190 so maybe it was to differentiate it? I would think it'd be plenty since people seem to love the slightly lower rated power of the good old 165HP GM L6 in these boats.

 

[kenny nunez]

The same engine that OMC used was called a 190. The 351 cam and heads bumped the extra 20hp and with a 4 barrel 225 hp.

 

[IslandExplorer]

The same engine that OMC used was called a 190. The 351 cam and heads bumped the extra 20hp and with a 4 barrel 225 hp.

Ah, that makes sense. The 351 heads and carb make quite a difference on this motor. Well I know just what to do then if the motor blows up. Thanks!

 

[Scott Danforth]

Ah, that makes sense. The 351 heads and carb make quite a difference on this motor. Well I know just what to do then if the motor blows up. Thanks!

Don't forget the cam which swaps cylinder firing order.

 

[IslandExplorer]

Don't forget the cam which swaps cylinder firing order.

Oh man, that'd be a terrible surprise once already all put back together.. Thanks!

 

[Scott Danforth]

Oh man, that'd be a terrible surprise once already all put back together.. Thanks!

that is why the 351 cam in the 351 and 302HO has a different firing order than the standard 302.

similar to the 4/7 cylinder swap on Big Block Chevys, the cylinder double swap leads to slightly better fuel distribution and a few ponies more

 

[IslandExplorer]

that is why the 351 cam in the 351 and 302HO has a different firing order than the standard 302.

similar to the 4/7 cylinder swap on Big Block Chevys, the cylinder double swap leads to slightly better fuel distribution and a few ponies more

I love information like this! For the better fuel distribution part- am I understanding this correctly that this means the different firing order in that situation helps the fuel distribution as in it flowing through the manifold and to the heads more efficiently? Just want to make sure I'm really getting what your saying.

 

[Scott Danforth]

I love information like this! For the better fuel distribution part- am I understanding this correctly that this means the different firing order in that situation helps the fuel distribution as in it flowing through the manifold and to the heads more efficiently? Just want to make sure I'm really getting what your saying.

Just google 4/7 swap and start reading