Automotive and Marine Engines?

[1973 Hondo]

Are they both the exact same, block heads etc? :confused:

[powerplay230]

Something I recently went through... Replaced a 454 in Bravo setup with a 502 H.O. That came from Scoggins Dickey, what seemed like a bargain quickly turned into one of those things that constantly had the wife saying sell the !?o? thing as is. I'm not an expert (except at breaking stuff) but I believe yes block and heads are the same. Off the top of my head things that will need changing are- intake (if saltwater), starter, flywheel, waterpump, starter, fuel pump (switched fron Mark IV), oil pan& pump, cam possibly to prevent reversion, might be more might be less depending on use and application. My bargain cost me a lot more than I expected... but with a few bolt ons Damn it runs better than the 454/330
Either way good luck and there are a lot of fantastic people on here that will help you with good advice. I would thank Ray but don't think he is on board anymore.
<Still not happy with 13 mph gain...

[gnarley]

powerplay230:
Still not happy with 13 mph gain...Not happy? What kind of boat is it, how long, what does it weigh & how fast is it now after the changes?

[disco_charger]

If I had a 13MPH gain, I'd be doing back flips.

[powerplay230]

Quick description- Big,Heavy,sled :) .Actually have been quite happy but after 1/2 a season you get so used to it, it's like no increase at all. My boat is never going to be fast its' a 89 Powerplay (now powerquest) 230 conquest, big and roomy for a 23' and unfortunately somewhere in the 4200-4400 lb range. Bought a 450/502 from Scoggins Dickey changed what my mechanic says I had to, added a world products bronze lined manifold, Edelbrock carb (believe is same as Weber) and Merc 4" manifolds thru hull. According to dwell tach I am only turning 4400 rpm with 23p bravo prop so maybe a change is needed there. Remember when your really slow a big increase is easier!
Thanks again for only site that is better than monthly magazine. :cool:

[powerplay230]

Oops at 4400 r I'm showing 64mph on speedo and tack.

[gnarley]

Sounds like you need to change props! You should get at least 4800 at WOT! It sounds like your lugging the engine with that prop & need smaller diameter or less pitch. I assume it’s a 3 blade & due to your weight the holeshot must suck, so a 4 blade might be worth a try also. Ask around to see what others are using with similar weight/engine & drive ratio combo's, I'd bet a 4 blade could really turn your performance around!

[paradigm shift]

73hondo> Block and heads are the same as for castings. Boat motors especially bigger boats see heavy loads and more consistant higher RPM than a car so usually clearances are a little different. Mainly ring gaps and piston clearances. We are talking a carb motor right. Just my .02
PP230 are you sure your tack is correct and speed. 4400 and 64 mph with a 23 prop is like 0% slip on prop? Depending on the cam you are running that 4400rpm if correct is leaving some HP on the table in my opinion. I would prop down a little to try and get the RPM up around 5000.
Nice motor and gains by the way. All my projects I just double my estimate cost to start because thats where it usually ends up anyway. :rolleyes:

[Clown]

H4ey
I have run the CHEVY 502 And have had PROBLEMS With the Guides Being To tight,You might want to look into that!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!
Its just a sugg estion REMeBER I dont kno=w Sh!tH. :p

[DEEZ NUTTS]

paradigm shift:
[All my projects I just double my estimate cost to start because thats where it usually ends up anyway. :rolleyes [/QB]Couldnt be better said!! I told my wife the new motor would cost 7,000$. It ended up twice that with a blower on top. I still dont hear the end of it.
Auto vs. Marine.....cam profile and brass freeze pugs. Other than bolt-ons my "car" motor has never missed a beat in a heavy 24' V.

[Havasu Hangin']

Clown:
I have run the CHEVY 502 And have had PROBLEMS With the Guides Being To tight,You might want to look into that...Yep. Teague recommends more piston-to-cylinder wall (forged pistons) and valve guide clearance cuz they run cooler than a car motor...
DEEZ NUTTS:
Auto vs. Marine.....cam profile and brass freeze pugs.Yep. Merc gets most of it's stuff from GM's truck division...

[powerplay230]

Guess I need to invest in another tach or another mechanic. 454 only turned 4400 rpm with 23p 3 blade. When 502 was first put in according to mechanic my tach was wrong by 400 rpm and it was really a pig. After some choice words (same words as when I got my bill) and adjusting time and carb it ran a bit better. It's still sluggish out of the hole but runs good from 2500 up which is what I expected with the weight etc... Will try to find out true rpm then try some props, will 4 blades lose much on the top end? If that doesn't work will have to tell the wife said it's terminal unless we add something called a blower!
Sorry to have stepped on your question Hondo.
Thanks again all!!!

[powerplay230]

Hondo, paradigm shift's advice is right on about cost of project, it's always double unless you start buying the neat pieces you really want.