MarineEngine.com - Your online store for all types of marine engines and boat parts.
PHONE ORDERS
Monday - Friday
9:00 AM - 5:00 PM EST
Click for TOLL-FREE Number
Online Checkout
Special $9.95 Flat Rate Shipping
(800) 209-9624 | Home | Contact | Shipping | Returns | Cart View your shopping cart.
Part Number Search
Shop by engine/drive part number.
Original & matching parts for sale.
Manuals & Accessories
Shop by description, item number
or manufacturer's model number.
Boat Repair Forum Boat Repair Forum   Boat Video Gallery Video Gallery
   
Click for MerCruiser parts and manuals!
Results 1 to 16 of 16

Thread: 3.7 Merc

  1. #1

    Default 3.7 Merc

    I am looking for opinions on 3.7 Mercruiser engines. Are they reliable? How about mileage? Parts availability? Thanks

  2. #2
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,181

    Default Re: 3.7 Merc

    Are they reliable? ............It depends upon who you ask.

    How about mileage? ............. Excellent power plant for weight to power ratio.

    Parts availability? ................ Manifolds are getting like hens teeth...very expensive.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  3. #3
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    4,029

    Default Re: 3.7 Merc

    Quote Originally Posted by ben47022 View Post
    I am looking for opinions on 3.7 Mercruiser engines. Are they reliable? How about mileage? Parts availability? Thanks
    Ayuh,.... It's Mercruiser's redheaded bastard step-child, they've Abandoned....

    It's most common part # is NLA....
    Any Grease is Better,... Than No grease at All....

  4. #4
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    2,957

    Default Re: 3.7 Merc

    Don't waste your time or your money.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Let the insanity begin.

  5. #5

    Default Re: 3.7 Merc

    I own one and I would advise you to find a 4.3 liter v-6 marine engine and rebuild it if you can. The drive ratio is compatible with the 3.7 or 470. The problem is that the parts are expensive and harder to get these days. They started building them in the early 70's and it pretty much stayed the same except for a few changes to certain components. They have these particular problems:
    1) OEM charging system sucks. Costs between $300-$400 to upgrade to an aftermarket alternator.
    2) Cam seals fail on older engines possibly causing engine failure by introducing coolant into oil sump.
    3) Plugs, wires, aftermarket pertronix electronic ignition will cost another $150-$200.
    4) Very prone to blown head gasket due to dissimilar cast iron head mated to aluminum block.
    5) Voodoo ritual to reinstall head. torque, run engine, remove valve cover, remove rockers on one side of head and retorque again. Pain in the arse.
    6) Don't dare overheat that particular engine or it could cost alot to fix.
    7) The cast iron exaust manifold and riser (log style) rot out on the older engines. Can also cause water intrusion usually into #3 and #4 cylinder which in turn can cause engine failure.
    8) Parts are getting hard to find because this engine system is considered antiquated. (I think they stopped producing them in 1989.)
    9) Quality rebuild parts that are available are expensive.
    Bottom line, there are better engines available today that can produce more horsepower and torque that you may or not require. Yes, the 470 is great on fuel and produces fairly decent torque but it comes at a cost. Also, don't get tired of turning wrenches because that never ends. lmao! Other than that, welcome to the world of boating! lol best of luck, Tom

  6. #6

    Default Re: 3.7 Merc

    Thanks all. I'll steer clear of that one.

  7. #7

    Default Re: 3.7 Merc

    I bought a larson with an 1989 3.7 closed cooled, I think they all are, been running it all summer, stator charging system and points ignition and all, runs like a champ, not one problem. if you do the maintanece they are fine, the last few years had the had aluminum manifolds. these so called experts are wrong, most never had one and only repeat what they have read.

  8. #8
    Join Date
    Jul 2008
    Location
    Northboro, Ma, USA
    Posts
    3,180

    Default Re: 3.7 Merc

    Quote Originally Posted by zackie77 View Post
    I bought a larson with an 1989 3.7 closed cooled, I think they all are, been running it all summer, stator charging system and points ignition and all, runs like a champ, not one problem. if you do the maintanece they are fine, the last few years had the had aluminum manifolds. these so called experts are wrong, most never had one and only repeat what they have read.

    Nice try.......You are indeed wrong.

    Most replying may have not owned one, BUT as like myself have worked on as many as 100 + over the years.....most have ended up in the scrap pile.

    If you had ever worked in the marine mechanic field you would know the history of this particular engine. Obviuosly you have NOT!

    Yes there are many that have survived and still run well, BUT it is only a matter of time before catastophic failure. GUARENTEED!!

    Not to mention the cost of replacing your stator based charging system.......

    Number 1 and or number 4 cyclinders will fail, only a matter of time..........


    I have personally seen ~ 6 or so in the last couple years that have died, RIP!!

  9. #9

    Default Re: 3.7 Merc

    maybe you are correct, my marine mechanic disagress with you, thats what he told me, I know of 2 other people that have that motor and love them, go figure.

  10. #10
    Join Date
    Jul 2008
    Location
    Northboro, Ma, USA
    Posts
    3,180

    Default Re: 3.7 Merc

    OK so that is a grand total of 4 including you.

    Again I have personally worked on over 100 of these motors.........thats 25 times more opinions than your small group of 4 people.

    IF and that is a very BIG IF, they are maintained properly and never run in salt water and have low hours on them and have never overheated, NOT ONCE, and have been winterized properly every year then maybe they might run good for a while.

    Eventually this motor will fail (and not like any other motor that will fail over time) it WILL HAPPEN.

    To quote other contributor's here......

    ""It's Mercruiser's redheaded bastard step-child, they've Abandoned....It's most common part # is NLA....(NO LONGER AVAILABLE)"

    and

    " Don't waste your time or your money.""

    With todays available engines, IE; the V6 there is no reason to go backwards in technology. That motor ended manufacturing in 1990, due to severe problems warrenty was extended into the mid '90's for so many inherent problems with the design...... (typical warrenty is 1 yr)

    Like anything else time and technology has done a much better job of replacing it......90% have become boat anchors and added a ton of ford 428/9 (i forget which head it is from exactly) big block heads to the automotive market.....

  11. #11
    Join Date
    Dec 2006
    Location
    Chaumont Bay, N.y., USA
    Posts
    4,029

    Default Re: 3.7 Merc

    Quote Originally Posted by zackie77 View Post
    maybe you are correct, my marine mechanic disagress with you, thats what he told me, I know of 2 other people that have that motor and love them, go figure.
    Ayuh,.... Just like a Drunk, yer livin' in Denial,.... Reality Will catch up with ya though,....
    Any Grease is Better,... Than No grease at All....

  12. #12
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,181

    Default Re: 3.7 Merc

    just like a drunk, yer livin' in denial,
    roflmao!!!!!!!!!!!!!!!!!!!!!!
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  13. #13

    Default Re: 3.7 Merc

    I have to say you guys stick together, you must be right, you can outpost everyone.

  14. #14
    Join Date
    Jul 2008
    Location
    Northboro, Ma, USA
    Posts
    3,180

    Default Re: 3.7 Merc

    Nothing to do with out posting,

    As far as I am concerned and I cant speak for anyone else BUT I do not feel any one here gives a crap about much to do with anyone elses issues.

    We as a bunch of "guys who stick together" do only one thing, try to help those who need help. The original post asked about this engine.

    We guys reccomended staying (running) away from it. Not because we stick together as I dont believe any one of us knows the other, we are all over the country....BUT isnt is strange that we all seem to have/share the SAME OPINION??????

    One would have to ask themselves why that is, dont you think?

    Also it is not a question of being right, it is a question of opinions from those who were asked and may have the appropriate knowledge to make a informed decision. Of course you voiced yours which was sort of the oposite of most everyone elses but if everyone with an opinion of that engine was to post it would have been at a minimum 10 to 1 against that engine......This is not the first post asking this exact question!!!!

    For a typical boat owner with no understanding of what they are buying/looking at, without a consistant opinion one way or another the person can make a ill advised decision when reading forums on the internet due to such a varied amount of opinions/responses to a post/question.......

    You should give us credit as we all seem to have the same opinion......that is a good thing for the original post/question. Now he knows what to expect and can make a informed decision......

  15. #15
    Join Date
    Sep 2010
    Location
    Jersey Shore
    Posts
    2,957

    Default Re: 3.7 Merc

    You can always ask around until you get the opinion that you want to hear.

    I have no fewer than six of these engines on my scrap pile right now.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Let the insanity begin.

  16. #16

    Default Re: 3.7 Merc

    Sorry men, did not mean to ruffle feathers and never said anything untrue about the 470. Sometimes, you just gotta learn the hard way. Time, money, hard work, and possibly lots of disappointment on this one. Been there and done it! Anyway, time to build something beast like instead! I eventually learned that torque is the key, of course with the right drive and prop combo. And finally, forget about economy in the boating world! It doesn't exist unless you own a Roman slave ship like the one in Ben Hur! lmao! Can you imagine? hahaha! By the way (kghost) I removed the heat exchanger on my 470 and did find a few rubber pieces at the inlet side of heat exchanger. You were right! Now I guess I will remove the lower unit and see if there is blockage or restriction in that particular area. What a pain in the ass! I had posted a good while ago about running hot issue at idle on trailer. Finally found time to work on it last weekend. Will do some more investigating tomorrow. later, Tom

Similar Threads

  1. 1978 454 merc with merc trans II and 330 outdrive
    By days_away in forum Mercruiser Sterndrive Forum
    Replies: 26
    Last Post: 01-19-2010, 06:48 PM
  2. Merc prop chart for a Merc 350 twin
    By fastjeff in forum Mercury Mariner Outboard Archive
    Replies: 2
    Last Post: 05-30-2009, 07:47 PM
  3. Merc 30 1989 to Merc 30 2006 engine replace
    By denithorne in forum Mercruiser Sterndrive Archive
    Replies: 3
    Last Post: 06-17-2006, 03:12 PM
  4. Can you use different merc lower units on a 1979 80 hp merc
    By c3h31a71d in forum Mercury Mariner Outboard Archive
    Replies: 1
    Last Post: 06-15-2006, 09:35 AM
  5. 650 merc 4cly lower unit swap with 3cly 650 merc
    By tackline in forum Outboard motors archive 2000-2004
    Replies: 1
    Last Post: 06-07-2002, 06:34 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •