How bad are Mercruiser 3.7Ls???

[mdlee]

So how bad are the Mercruiser 3.7L? I Looked for years trying to find a 26? Stamas Hard top with twin motors. I found one for a good price with 1986 190hp 3.7Ls. I bought the boat, the motors have low hrs on them I have been working on the motors going through the cooling system and such. The motors sat for maybe 2yrs. I have both motors running now, and hope to start using the boat soon?. The thing is I do a lot of offshore fishing, and have used mostly big outboards. Are these motors going to give me good service if I maintained them, or are they destine to fail? I fish offshore maybe 1 to 2 days a week, do u fellas think these motors are going to stand up to that .. I have been reading in this forum for a few months now, and everyone seems to hate these 3.7L? I just don?t want to spent to much money on a lost cause.

 

[TilliamWe]

Re: How bad are Mercruiser 3.7Ls???

... Are these motors going to give me good service if I maintained them, or are they destine to fail?...

Yes and Yes

 

[ezmobee]

Re: How bad are Mercruiser 3.7Ls???

The only thing worse than 1 is 2.

Correct me if I'm wrong experts but won't saltwater exaggerate the 470's dissimilar metals problem?

 

[gettin'even]

Re: How bad are Mercruiser 3.7Ls???

ohhh boy..........

 

[Don S]

Re: How bad are Mercruiser 3.7Ls???

Correct me if I'm wrong experts but won't saltwater exaggerate the 470's dissimilar metals problem?

Nope, the motor has a closed cooling system


They are lake and bay motors, NOT offshore motors.

 

[mdlee]

Re: How bad are Mercruiser 3.7Ls???

I think im gunna be sick... Don how long do u think they will last running them offshore? If I can get 3 or 4yr out of them I will be happy, then repower

 

[Don S]

Re: How bad are Mercruiser 3.7Ls???

If I can get 3 or 4yr out of them I will be happy,

So would a lot of other people.
Be realistic here for a second, we have no clue to the condition of your engines now, nor the kind of maintenance you do or how you run and engine, or the load on the boat or anything else. The answer you need comes for a crystal ball, or a reader of the future. Not a mechanical forum.

PS:
I wouldn't run them off shore if I rebuilt them myself.

 

[mdlee]

Re: How bad are Mercruiser 3.7Ls???

What is it about the 3.7L that makes them so bad Offshore?

 

[Don S]

Re: How bad are Mercruiser 3.7Ls???

Dependability

 

[mdlee]

Re: How bad are Mercruiser 3.7Ls???

I see. Well I guess I need to sell this thing.. It does run good though. This is my first I/O, I really didn't do my Home work on this one. Thanks for the Help fellas, now I know, The bad news is still better than being broke down 10mi out.

 

[ErieRon]

Re: How bad are Mercruiser 3.7Ls???

Oh ye of little faith...

Don is right about the crystal ball thing. There's no telling unless you go through them thoroughly. If they've been "loved", and have had the issues addressed that gave them a bad rep, they'll serve you well. If not, your in trouble. I have a 1984 470 (basically the same motor). I took care of mine and fish Lake Erie exclusively. Although it's not salt water, it's a tough lake. I have no second thoughts of running mine to wherever the fish are, and I only have a single. I've been towed in twice. Once, the first year I owned it for a faulty voltage regulator (Merc factory recall), and this past July when I spun my engine coupler...after 25 years.

Read up...here and at breezeworks.com and get familiar with the issues. Then, do some digging into those engines and make an informed decision.

Good luck.

 

[mdlee]

Re: How bad are Mercruiser 3.7Ls???

I did pull the head on the starboard motor to see what it looked like.. It had new pistons .10 over.. Maby it will work out for me. My thought was " alot of hp out of 2 4cyls". For an outboard person like my self the thought of allmost 400hp out of 2 alum 4cyls was pretty sweet. Thanks for the good word Buddy. I will check out those sites for sure.

 

[TilliamWe]

Re: How bad are Mercruiser 3.7Ls???

I did pull the head on the starboard motor...

Oh, jeez, that was the WORST thing you could have done! Please, please, please read and follow the Mercruiser manual that says how to reinstall the head. Those engines have an open deck, and getting the head on properly is a MUST, or you will blow the headgasket. Best of luck to you..

 

[zbnutcase]

Re: How bad are Mercruiser 3.7Ls???

They are great engines and i'm sick of the bashing they receive here. And replacing the iron head with aftermarket aluminum 460 head (like the Edelbrock #60669) installed with studs creates an all aluminum engine and cures the rare head gasket problem ( I have changed 1 in 23+ yrs). Yes the charging system is junk but easy fix. I have a customer who has a pair of em' bought new in '85 and has been using them offshore since with nothing more than regular PM and a pair of alternator kits. 'nutcase

 

[Bronc Rider]

Re: How bad are Mercruiser 3.7Ls???

I did pull the head on the starboard motor to see what it looked like.. It had new pistons .10 over.. Maby it will work out for me. My thought was " alot of hp out of 2 4cyls". For an outboard person like my self the thought of allmost 400hp out of 2 alum 4cyls was pretty sweet. Thanks for the good word Buddy. I will check out those sites for sure.

Those engines were rated at the crank not the propeller. I read an article that said they have similar performance to the prop rated 3.0 130hp engine.
With two engines I would feel safe enough to go offshore. As long as the hull is up to the task you might as well go out and enjoy it.

 

[stonyloam]

Re: How bad are Mercruiser 3.7Ls???

Yes and Yes

I would agree with that. I have never been towed in (since "91"), but there are things that will wear out and have to be fixed. I would go with an aftermarket alternator kit, and make sure that the cooling system is in good shape, if taking it offshore. Make sure that you put the head back on EXACTLY as the manual says, and use a OEM Mercruiser head gasket. Good luck.

 

[mdlee]

Re: How bad are Mercruiser 3.7Ls???

Oh, jeez, that was the WORST thing you could have done! Please, please, please read and follow the Mercruiser manual that says how to reinstall the head. Those engines have an open deck, and getting the head on properly is a MUST, or you will blow the headgasket. Best of luck to you..

Yes I did read the manual,,

 

[TilliamWe]

Re: How bad are Mercruiser 3.7Ls???

Yes I did read the manual,,

Okay, but did you do exactly what it said to do?

 

[mdlee]

Re: How bad are Mercruiser 3.7Ls???

Yes sir I did exactly what it said.. I will say though when I pulled the head I was taken back by the layout of the crank case.. You are right it is a very strange motor. Just an FYI for any one like my self that might be new to these motors. My starboard motor seemed to be locked up when I got it, turns out the magnets on the flywheel were broken off and had completely immobilized the crank. This is not something I considered at first. It took me 2 days to figure it out. These motors also seem very sensitive to timing and gap settings even a .01 seems to make a very big difference. Maybe this will help some save a little time. Thanks to all for your help

 

[DACEAC]

Re: How bad are Mercruiser 3.7Ls???

I bought mine a year ago in a '86 fourwinns 3.7 190hp. the only trouble it has given me is that it is hard starting til it warms up. gonna rebuild carb in spring when i do a tune up and hopefully cure that problem. other than that I treat it like an outboard where i put the battery charger on friday night just to make sure the batteries are good to go. good luck with yours.