Time to chuck the 470

[QBhoy]

You guys are a wealth of knowledge. I do appreciate it. Also, not sure why nola_mike swap thread didn't pop up when I did my initial search before asking in this thread. THAT is a vast amount of knowledge! So thanks.

NOW unto my current situation..... I had a long time customer come by the shop today and looked at the boat. During the conversation I mentioned issues with the 470 and mentioned a 4.3 (that is my leaning) but then he said he "thinks" he might have a good 3.0L sitting in his barn and if so I could have it for nothing. Like I said before I am not necessarily needing speed over reliability, so the 3.0 would probably do ok for me. I already have a 69 Mustang with a 460 for speed needs. Other than the gear ratio issue and prop change, anything else that would have to be done to swap from the 470 to 3.0? Thanks.

Honestly now. The gear ratio isn’t an issue. Worst case…you’ll maybe just need to change the prop…if at all.
What 3.0 is it you can get your hands on ? What kind of age is it ? Just check it over first perhaps. Look out for signs of a cracked block, from frost damage perhaps. Only thing that can really kill a 3.0 is it’s owner and lack of care. If it’s anything recent, sounds a good deal !

 

[Scott Danforth]

fuel economy and boating are a dichotomy

 

[Dubed]

fuel economy and boating are a dichotomy

Yep. Paying for fuel for the boat is stupid expensive. But in the scheme of things, it's really the least of your worries lol

 

[QBhoy]

fuel economy and boating are a dichotomy

Great word there. Love it Scott . Think you’re mostly right there for 99% of pleasure boaters. I might be the exception perhaps. I use my wee outboard 19ft cuddy that frequently, should she not have a modern 4 stroke merc on her…and instead, have the inboard or older 2 stroke in/on her…jeez, I’d be likely be considerably less well off. I’ve clocked up nearly 1300 hours in her, in 3 years !
Compared to the other 2 boats (although very different things) with their v6 2 stroke outboard and the v8 mpi…there is a considerable difference in their fuel consumption. The v6 2 stroke is just silly bad…the v8 mpi is exceptionally frugal when cruising for what it is…but still about 25% thirstier in the 20’s, where I spend most of my time. Twice as bad going slow. Anyway. I get what you mean. But makes a difference to me at least.

 

[flashback]

No one here has a crystal ball

 

[Scott06]

I already have a 69 Mustang with a 460 for speed needs. Other than the gear ratio issue and prop change, anything else that would have to be done to swap from the 470 to 3.0? Thanks.

I would do the swap get it in the water then play with prop pitch and gear ratios in that order.
usual fuel line, linakge, shift plate mounting. Biggest concern is the exhaust down pipe not sure if the 3.0 and 3.7 use the same down pipe and if it can be finagled to fit or modified by using hard-wall exhaust hose.
if you did a car engine swap this will be easier.

wife and i just went for a cruise in my 65 gto, post a pic of the stang if u have one easily available

 

[Scott06]

fuel economy and boating are a dichotomy

Absolutely when compared to fueling up the car, but when you put the fuel costs vs other family pastimes it seems cheap compared to other things.

 

[QBhoy]

I would do the swap get it in the water then play with prop pitch and gear ratios in that order.
usual fuel line, linakge, shift plate mounting. Biggest concern is the exhaust down pipe not sure if the 3.0 and 3.7 use the same down pipe and if it can be finagled to fit or modified by using hard-wall exhaust hose.
if you did a car engine swap this will be easier.

wife and i just went for a cruise in my 65 gto, post a pic of the stang if u have one easily available

Same exhaust down pipe used too. Far as I know.

 

[Lou C]

Don’t think the 3.0 has the torque for a 19’.
4.3 swap a lot more work but worth it. Ideal engine for a 19’.

 

[QBhoy]

Don’t think the 3.0 has the torque for a 19’.
4.3 swap a lot more work but worth it. Ideal engine for a 19’.

No doubt the 4.3 be better all round. But all I was thinking is effort and cost versus the drop in 3.0. Especially if it’s free. The wee 3.0 will do just fine I’d think. Plenty of fairly heavy generic 17-19ft boats have them to be fair. Maxum, bayliner, searay, regal, and the rest. 135-140hp from these wee things pushes the above mentioned boats to 40 mph gps, when well propped and an easy late 30’s when propped in the middle for towing stuff. Props are that good these days, you can get away with so much. Sure I learned to wake board from a 18ft maxum with a 3.0. Stuck a hi 5 on it and it’s was fairly impressive at pulling from a standstill deep water.

 

[Scott06]

Don’t think the 3.0 has the torque for a 19’.
4.3 swap a lot more work but worth it. Ideal engine for a 19’.

Correct but depends on how he uses it. My typical use is 6-8 people doing watersports… cant have enough hp. If its him spouse and a friend or two cruising stop for a swim, get a low pitch prop and a 3.0 will putz along just fine and be real easy to maintain…

Same exhaust down pipe used too. Far as I know.

didnt know that for sure then yes it is basically bolt in assuming front mount is in same or close enough spot.

 

[QBhoy]

Correct but depends on how he uses it. My typical use is 6-8 people doing watersports… cant have enough hp. If its him spouse and a friend or two cruising stop for a swim, get a low pitch prop and a 3.0 will putz along just fine and be real easy to maintain…

didnt know that for sure then yes it is basically bolt in assuming front mount is in same or close enough spot.

Yeah. Mount is the same too. Only know because of the earlier mentioned friends boat. The local merc guy sold him a new 3.0…it was installed and running same day dropped straight in, where the 3.7 came out. Identical mounts and all other fittings generally.
Yeah. I get what you say about depending on use. No doubt you’re right…but I honestly was surprised at the lack of real difference between the power of the two engines. The 3.7 when it did work ok…had a little more grunt out the hole. But other than that…next to no different otherwise. That 3.7 he had I’m sure was a 165-170hp thing. On its best day perhaps.

 

[Lou C]

Ahh well if its that easy, then I see the point. A lot less work than a conversion, and less unknowns for sure. Perhaps use a 2" lower pitch prop to get a bit more response out of the hole making sure it doesn't over-rev the 3.0. The only negative thing about those engines I've heard is they are prone to blown head gaskets due to detonation, so putting it in a heavy boat I would use at least 89 if not 93 octane gas.

 

[QBhoy]

Ahh well if its that easy, then I see the point. A lot less work than a conversion, and less unknowns for sure. Perhaps use a 2" lower pitch prop to get a bit more response out of the hole making sure it doesn't over-rev the 3.0. The only negative thing about those engines I've heard is they are prone to blown head gaskets due to detonation, so putting it in a heavy boat I would use at least 89 if not 93 octane gas.

Yeah. Think it’s usually the go too engine, after the 3.7 gives in. For some reason…there were a a huge number of boats here fitted with these things, in the late 80’s. Fletcher boats in particular for a while. 99% of these boats now, have been engined with a 3.0 now. The guys that want the best from the boat afterwards usually drop a little pitch. Some I know, didn’t bother. The 3.0 is likely the most successful and numerous engine ever fitted to a boat over the years. Harsh on the ear…but reliable as they get. Every second boat in my marina has one. Be the same story all over Europe too.

 

[Lou C]

And you can still buy one brand new, at least here in the USA.
Yep they are simple as can be, like the cast iron inline 6s we had on our American cars when I was growing up:
GM: 250 Cu in inline six was available in a 292 cu in version for trucks, Mercruiser used these in boats as well.
Ford: 200 cu in inline six, 250 cu in inline six and the best of all, 300 cu in line six for trucks
Chrysler: 225 cu in slant six, used in millions of taxis.
American Motors/Jeep 232, and 258 cu in sixes used in AMC cars and Jeeps, later updated to the legendary 242 cu in Jeep six. These continued to be built by Chrysler till 2006, I think they built 5 million of them in Kenosha Wisconsin. I miss those simple cast iron beasts! Still have one, in our '98 Jeep. 180,000 miles and runs like new.

 

[QBhoy]

And you can still buy one brand new, at least here in the USA.
Yep they are simple as can be, like the cast iron inline 6s we had on our American cars when I was growing up:
GM: 250 Cu in inline six was available in a 292 cu in version for trucks, Mercruiser used these in boats as well.
Ford: 200 cu in inline six, 250 cu in inline six and the best of all, 300 cu in line six for trucks
Chrysler: 225 cu in slant six, used in millions of taxis.
American Motors/Jeep 232, and 258 cu in sixes used in AMC cars and trucks, later updated to the legendary 242 cu in Jeep six. These continued to be built by Chrysler till 2006, I think they built 5 million of them in Kenosha Wisconsin. I miss those simple cast iron beasts! Still have one, in our '98 Jeep. 180,000 miles and runs like new.
View attachment 371971

Agree. Been around since the late 70’s in that 3.0 140hp form. Still about with little changed over 4 decades later. Challenge anyone to suggest a more successful or numerous engine ever put in a boat. Can’t argue with their tried and tested story really.

 

[teardropty]

Well, I went earlier today to pick up the "new 3.0". Guess what? It was a 3.7 470. The guy giving me the motor sincerely believed he still had a couple of 3.0's sitting around and was more than happy to let me have one for free. The good news was that he was more than happy to let me have another 3.7. lol Sadly his 3.7 had the same issue that my current 3.7 has, namely a rotted cast iron exhaust manifold system.

 

[ROY WILLIAMS]

Well, I went earlier today to pick up the "new 3.0". Guess what? It was a 3.7 470. The guy giving me the motor sincerely believed he still had a couple of 3.0's sitting around and was more than happy to let me have one for free. The good news was that he was more than happy to let me have another 3.7. lol Sadly his 3.7 had the same issue that my current 3.7 has, namely a rotted cast iron exhaust manifold system.

look up the 470 used parts exhaust manifold ..
my 470 engine has the coolant and the distilled water .... I did not use the coolant leaks .....1978 eng 470 ..

New MerCruiser Exhaust Manifold 470 & 485 OE # 71527A8/71527 | eBay

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[Scott Danforth]

Well, I went earlier today to pick up the "new 3.0". Guess what? It was a 3.7 470. The guy giving me the motor sincerely believed he still had a couple of 3.0's sitting around and was more than happy to let me have one for free. The good news was that he was more than happy to let me have another 3.7. lol Sadly his 3.7 had the same issue that my current 3.7 has, namely a rotted cast iron exhaust manifold system.

Find an aluminum manifold

 

[nola mike]

Find an aluminum manifold

I wonder who would have those laying around? Op, shoot me a pm if you'd like.