1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

[jmw129]

There a 1986 Thompson with a 3.7L / 170hp for sale and I really like the boat but I need to know honestly is this engine a piece of junk?

I had a 1987 Larson with a 3.7L / 165hp and sold it because my mechanic told me it was a money pit & basically a Mutt engine.

The reason why he called it a Mutt was because the Mercrusier (GM) had a Ford Big Block which he said they only made for a couple of years & they had alot of problems with this engine PLUS he
said parts are very hard to get & very pricey.

I really like this Thompson and the guy say's it runs great & he is asking $1,650 but I don't want to buy a piece-of-crap either... Don't me get me wrong here, maintance is one thing but I'm not in
the mood to dump a grand or two in this boat.

I need to hear from people who know alot about this engine, know people that had this engine, or worked on them.

Thank you in advance for your help!!

 

[Lyle29464]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

I would pass. Too many other rigs out there.

 

[jmw129]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

Why would you pass? Do you know anything about this engine?

 

[dollarten]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

There a 1986 Thompson with a 3.7L / 170hp for sale and I really like the boat but I need to know honestly is this engine a piece of junk?

I had a 1987 Larson with a 3.7L / 165hp and sold it because my mechanic told me it was a money pit & basically a Mutt engine.

The reason why he called it a Mutt was because the Mercrusier (GM) had a Ford Big Block which he said they only made for a couple of years & they had alot of problems with this engine PLUS he
said parts are very hard to get & very pricey.

I really like this Thompson and the guy say's it runs great & he is asking $1,650 but I don't want to buy a piece-of-crap either... Don't me get me wrong here, maintance is one thing but I'm not in
the mood to dump a grand or two in this boat.

I need to hear from people who know alot about this engine, know people that had this engine, or worked on them.

Thank you in advance for your help!!

You mechanic , like I once was sees all the bad ones comes in and gets prejudiced like I did I am sure there are thousands out there that a running good Ask him to give you a water test in it and check the oil pressure and water temp and go from there Also look for an updated alternator . It would look conventional like current ones not , buried under the front engine pulley

 

[jmw129]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

You mechanic , like I once was sees all the bad ones comes in and gets prejudiced like I did I am sure there are thousands out there that a running good Ask him to give you a water test in it and check the oil pressure and water temp and go from there Also look for an updated alternator . It would look conventional like current ones not , buried under the front engine pulley

Since you were a mechanic and know a good amount about this engine would I be out-of-line requesting to perform a compression test on this engine? I have a compression gauge and of course you hear all kinds of advice on how to compression an engine.

The 3.7 / 165hp (1987) I used to own had alot of torque but blew antifreeze / over heated on me & my mechanic told me it was a $2400 repair because the water pump was burried on the bottom of then engine.

Sound accurate to you?

Sucked having to get towed back. That was last season and since then have been using my other boat with an OB and so far has been one tough engine. Make's me really wonder is IB / OB are built better than OB's???

 

[stonyloam]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

Forget it! Just by reading your question, you would not be happy with it.

 

[boattoy]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

my 470 itself hasnt been my main issue. Ive had starter/fuel/ignition issues which were all not related to the motor itself. could happen with any motor. The motor itself runs great and thats after it sat for 15 years locked up.IMO when they run right, they run great. Ide much rather have a 4.3 but they aren't THAT bad. if it looks like its been neglected ide pass though. thats goes for just about any used boat from now on for me.

 

[jmw129]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

So the 4.3L overall is good? What about the 5.0 or 5.7?

 

[Eric 3.7LX Alpha 1]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

They are all good engines on their own. But with boats, maintenance is everything.

 

[badkins50]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

As Eric said it's all about the maintenance history of the motor (any motor for that matter) and yes that goes for the 3.7L too. The problem with these motors is overheating them because of the design aluminum block with cast iron heads (or the other way around, I can't remember now) you can cause a lot of damage so it is advisable to change the impellor and clean out the water flow system every year and my impellor was in the lower unit of the outdrive which only took me a good morning to change out and maintain. I had the 470 that was well taken care of and the only problem I had was the carb rebuild and the mechanical fuel pump went bad but on a 26 year motor that isn't bad. Mine had all the nescessary upgrades needed on these engines already though (alt & 4" exchanger). It will require more attention than the others but I give our 5.7L the same amount of attention because lets face it, you can not get out and walk to the nearest gas station. Good luck and remember research everything before buying any boat.

 

[dollarten]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

Since you were a mechanic and know a good amount about this engine would I be out-of-line requesting to perform a compression test on this engine? I have a compression gauge and of course you hear all kinds of advice on how to compression an engine.

The 3.7 / 165hp (1987) I used to own had alot of torque but blew antifreeze / over heated on me & my mechanic told me it was a $2400 repair because the water pump was burried on the bottom of then engine.

Sound accurate to you?

Sucked having to get towed back. That was last season and since then have been using my other boat with an OB and so far has been one tough engine. Make's me really wonder is IB / OB are built better than OB's???

A compression test would not be a bad idea but ,if the seller thinks you are getting too invasive , I would crank the engine over with the coil wire removed and grounded and listen very carefully to the tone of the starter . It should have a very even sound as every cylinder is coming up on the compression stroke . If there is a weak one , you will hear the starter picks up a little speed when it gets to the bad cylinder . .This little test save me an en engine once when I was racing I heard the starter pick up speed when it came to an offending cylinder as the exhaust valve was cracked and ready to brake off upon disassemble of engine . The was on a eight cylinder and was still an easy sound to pick up

 

[bthadude]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

I would stay away from that engine.I have one and it's expensive for parts and alot of them you can't buy new anymore.This was a one off production by Ford strictly for marine use, it's half of a ford 460.So that being said they stopped production about 22 yrs ago and parts are getting hard to find.If you do buy it make sure you have a 4" heat exchanger and get rid of original charging system (extemely expensive to repair) and get the alternator conversion kit.

 

[natemoore]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

I might pass if there were a similar boat with a 3.0L or 4.3L, although I'm not getting rid of mine. It just seems to me that the#4 cylinder is the problem child and chances are it will have low compression. Other designed-in potential problems others have mentioned.

It's kind of like having a petite, but well endowed wife that requires a lot attention, lots of touching, lots of talking to, lots and lots of listening to to keep her happy, and keep you getting some WOT when you want it, versus a big-boned and stout, but loyal and dependable wife you only have to take out to dinner every once in a while, but otherwise ignore most of the time and still get the WOT.

I've been able to find all the parts needed to do a complete rebuild, even though Quicksilver doesn't manufacture many of the replacement parts anymore. I used Ford 460 pistons, rings, bearings, push rods, and hydraulic lifters. OEM gaskets, oil pumps, fuel pumps, carb kits are easily found. Reservoir/exhaust risers and manifolds are available. Plenty of used parts on ebay. I've rebuilt practically every system on the boat. The only thing I can't find new would be the power steering valve assembly, but I've seen them used on ebay. I was able to find the OEM stainless steel tubes and power steering hoses that go on it. Don't let the "parts are hard to find" excuse stop you from getting it.

 

[iflyfl340]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

i have the 3.7 i love this motor my little 16 ft boat can run better then most of the boats i thing plus the power is nice

 

[Bondo]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

There a 1986 Thompson with a 3.7L / 170hp for sale and I really like the boat but I need to know honestly is this engine a piece of junk?

I had a 1987 Larson with a 3.7L / 165hp and sold it because my mechanic told me it was a money pit & basically a Mutt engine.

The reason why he called it a Mutt was because the Mercrusier (GM) had a Ford Big Block which he said they only made for a couple of years & they had alot of problems with this engine PLUS he
said parts are very hard to get & very pricey.

I really like this Thompson and the guy say's it runs great & he is asking $1,650 but I don't want to buy a piece-of-crap either... Don't me get me wrong here, maintance is one thing but I'm not in
the mood to dump a grand or two in this boat.

I need to hear from people who know alot about this engine, know people that had this engine, or worked on them.

Thank you in advance for your help!!

Ayuh,.... Of all the threads you've been posting lately, yer shoppin' for boats with Long Dead, 'n Gone drivelines...
You had a 470 that's a POS, 'n now ya want Another of the same motor,..??
A short rule of thumb when shoppin' CHEAP boats is,...
Never buy a boat with a 470 Merc, or an OMC Stringer drive...
'n, CHEAP boats are Cheap for a Reason...

You've already stated yer Not a Mechanic,...
Buy yerself a boat with a Chevy motor, 'n either a Merc or Volvo driveline...
'n newer than the early/ mid 80s...
So far, every boat you've asked about are pretty much something that the Owner has to be his own mechanic, or the labor bills are gonna kill ya...
'n that's not even takin' into account the NLA parts for these Antiques...

 

[Don S]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

Ayuh,.... Of all the threads you've been posting lately, yer shoppin' for boats with Long Dead, 'n Gone drivelines...................................

All that typing, and your posting to a 2 month old thread brought back to life ...................

 

[Bondo]

Re: 1986 Mercruiser 3.7 Liter / 170Hp Good or Bad Engine? Please Help!!!!!

All that typing, and your posting to a 2 month old thread brought back to life ...................

:facepalm: :facepalm: Well,... What can I say,...
The OP is still here, 'n still askin',...