nOOb I/O question 3.7 vs 3.0

yodaddy · #1 09-23-2009, 02:19 PM

I just purchased a 1978 V20 Cuddy without a motor. With a limited budget on this project, it's come down to 2 choices for powering the boat. Option #1 is a 1992 3.0/140hp previously owned and maintained by a Merc mechanic, and option #2 is a 1988 3.7/170 in very good condition. I've read plenty about the 3.7 problems, and would put on an aluminum head and external alternator before hitting the water if I were to go that route.

I'm a newbie here, and have been reading the forums (and not doing much else) for the past 2 weeks, and am very impressed by the depth of knowledge offered up by members. Any opinions as to the functionality of either of these motors over the other in a V20? Does a 3.0 140 have enough stones to push a V20 at reasonable speeds?

Thanks!

RidgeRunner · #2 09-23-2009, 03:20 PM

I am new here also. What a wealth of knowledge. Congrats on the purchase. Unfortunately, my knowledge on I/O's is poor. Not a lot of activity today but someone will post in shortly. Good luck.. Vic

yodaddy · #3 09-23-2009, 03:33 PM

A fellow noobie...thanks for the greet!

Just sitting here refreshing my browser in anticipation of the wisdom soon to be dispensed by the V20 Masters.

Bonita Dan · #4 09-23-2009, 04:34 PM

Depending on the type of boating ya plan on doing the 3.0 will work but it won't be anywhere near a speed demon with only 140hp. The 3.7 would have been a much better choice with an aluminum head but the rest of the parts are becoming more rare and very expensive when found. Mercury really stuck it to everyone when they scrapped the 3.7 instead of finding a solution to there problems. I let them know at 2 international boat shows back in the nineties when my exhaust manifold went bad and there was no replacement made. Second time I was nearly arrested but got my point across to higher ups in the Corporation.

My option these days is to install a 4.3 in the '85 but don't think it will fit in your application. If money wasn't an issue,I would drop in a diesel if I where you. Best of luck with your quest.

yodaddy · #5 09-23-2009, 05:04 PM

Thanks for your input.

The boat will be used for offshore fishing in New England. I plan on running a gas motor for a year or two, then upgrading to a diesel.

Was your 3.7 in a V20? If so, what was your top end speed?

spareparts · #6 09-27-2009, 02:26 PM

you best bet will be a 5.0L v8. They are generally cheaper than the V6, give roughly the same hp as the 4bbl v6 with a lot more torque. They've been building them forever(it seems that way) so there are a lot of used ones and plenny of parts and suppliers. They are easier to work on than teh Most of the ones I've seen actually give better cruise fuel consuption than the v6. the 5.7 is thT same weight and size, but they usually carry a premium price tag. The 3.7 was a good motor in its better days(87 and later). But they are getting scarce and expensive. The 3.0 will work, buts its going to be working hard(and burning lots of fuel for the speed)

yodaddy · #7 09-27-2009, 04:08 PM

Thanks for your input. I was originally looking at an '88 3.7, and have since found an '89 with 3-400 hrs on it. Haven't seen it in person yet, but if everything checks out and it runs good it's coming home with me :)

cfelton · #8 10-05-2009, 06:45 PM

Welcome to the site!! Sounds like you're leaning towards a 3.7. They're good motors, and their problems are easily fixed. My 170/470 gets really good gas milage and has plenty of power. I've topped out at 42mph with 2 adults and 3 kids, trimmed up and tached out. I love my 170!! Good luck with yours!

yodaddy · #9 10-06-2009, 10:58 PM

Quote:

Originally Posted by cfelton

Welcome to the site!! Sounds like you're leaning towards a 3.7. They're good motors, and their problems are easily fixed. My 170/470 gets really good gas milage and has plenty of power. I've topped out at 42mph with 2 adults and 3 kids, trimmed up and tached out. I love my 170!! Good luck with yours!

Thanks for the welcome, and your input.

I bought one of each, a 3.0 and a 3.7. The 3.7 is an '89 165hp and runs like a brand new motor. I'm swinging it into my '78 V20 Cuddy, and will keep the 3.0 as a backup motor. The 3.7 is currently in a 17' Larson All American, and pushed it to 47mph (GPS) on a mirror calm lake a couple of days ago.

bowhunter510 · #10 10-11-2009, 12:47 PM

Good after noon to all IM new here and I just purchased a 1987 v want to know why would anyone want to use a aluminium ford 460 head on a mercruiser 165 thanks.