NEED HELP ABOUT 3.7 Mercruiser?

W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
i bought a 19ft Monteray that has a 3.7 motor...took it out and 15 minutes it was red hot and shut off...let it cool off and got it back to the dock...the closed system will NOT hold water....the oil is clean ,,,and it also has a new lower unit pump...any suggestions on fixing this motor...and another question i have is can this be changed to a v-8? ...or better to repair or rplace this motor?:confused::confused::confused:
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: NEED HELP ABOUT 3.7 Mercruiser?

wkentucky57 said:
i bought a 19ft Monteray that has a 3.7 motor...took it out and 15 minutes it was red hot and shut off...let it cool off and got it back to the dock...the closed system will NOT hold water....the oil is clean ,,,and it also has a new lower unit pump...any suggestions on fixing this motor...and another question i have is can this be changed to a v-8? ...or better to repair or rplace this motor?:confused::confused::confused:
Click to expand...

Howdy,


Welcome aboard!

Well, it would have been "better" to have asked the question before you bought it. Then most of us would have told you to run away from it! (the obsolete 3.7L engine!)

If you didn't damage the engine by blowing the head gasket etc, that may already be the problem......... You also might have a riser or riser gasket leak that is allowing the coolant to leak overboard or a leaking heat exchanger.

You'll just have to troubleshoot the entire cooling system to find it.

Once you 'fix' it, The 3.7L actually a pretty good running engine. They do have their own unique problems though.................

Stand by. The 3.7L "crowd" will be by in a moment!


You can certainly replace the entire engine either with a long-block or rebuilt engine if required. It may be an easy fix though.

Also, you can replace the engine with a different one (V-6/V-8) but you'll have to replace the drive too. yours is the wrong ratio for either.

AND it won't be cheap. Might be better to just sell it quick and put your money into a boat that is set up the way you want.


Good luck!


Rick
 
Bt Doctur

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,112
Re: NEED HELP ABOUT 3.7 Mercruiser?

Evidently there was no test run before purchase.The 3.7 holds anti-freeze not water. So explain the does not hold water part.
does it leak inside the boat? ,missing drain plug in the heat exchanger ?Was any work done prior to purchase?
 
S

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Re: NEED HELP ABOUT 3.7 Mercruiser?

Go to Autozone and borrow the tools to do a compression check and a cooling system pressure test, let us know the results. Here is the manual, http://boatinfo.no/lib/library.html you want either Mercruiser manual #3 (early) or #8 (late)
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

well the water isnt running inside the boat ....but ill have to get a compression chack on it...as of right now i have it one a local web site trying to sell it as is....i put a new floor in it new lower unit pump and vynil all the faded blue ....so im hoping just to sell and wait til spring...but ill still check what i can before i put it up for the winter,,,had 2 over the phone fix prices and each were starting out at $1000 dollors ....really thank everyone for the help...that will at least give me a starting point
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: NEED HELP ABOUT 3.7 Mercruiser?

........as of right now i have it one a local web site trying to sell it as is................had 2 over the phone fix prices and each were starting out at $1000 dollors
Click to expand...

Those are totally bogus. NO ONE will know until it's carefully inspected. If you do sell it PLEASE tell the buyer exactly what it's doing.
(they'll probably show up here wondering what's wrong and asking what to do!!)
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

i have explained that the motor needs work and that all i want is $3000.00 thats below what i have in the boat but cut my losses and sell!!!!
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

well anyone that knows boats says that they would love to have it IF it wasnt a 3.7,,,,now my other question is,,,i build small block chevy race motors all the time...now if i build a stock small block with marine cam and marine intake with marine manifolds will this work? safely?
 
Bt Doctur

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,112
Re: NEED HELP ABOUT 3.7 Mercruiser?

A plug and play 5.7 is about $5600.00 , The $3000 for yours sounds very overpriced in "not running condition"
You need to find out whats happening to the water that comes from the drive, thru the heat exchanger ,and out the riser.
could be somrthing as simple as the wrong gasket used.
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

well $2500 is what i gave for the boat had a new floor put in it and new lower unit pump put in it...but any way...i looked on the motor and not knowing nothing about this motor...i have discoverd they took the damn heat exchanger OFF THE BOAT and rerouted the water hoses...
sp now what is a good heat exchanger going to cost for this boat?
 
S

stonyloam

Vice Admiral
Joined
Mar 13, 2009
Messages
5,827
Re: NEED HELP ABOUT 3.7 Mercruiser?

Man you got boned big time! If they tried to run raw water, no wonder it got hot, I don't think the thermostat would ever open, and the water is going to trash the cam seals, and rust the cam end, to say nothing of the trash that gets pumped in. Look for a exchanger on e-bay, and get the water out of the block and antifreeze in there asap. Can you get your money back?
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

well getting money back not going to happen...the guy was an ******* when i called him after i took the boat out on the lake...so im hoping i can fix it...ive done spent 500 on it fixing other stuff
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: NEED HELP ABOUT 3.7 Mercruiser?

Yeah. You REALLY need to put the engine back the way Merc designed it. It won't run well very long without closed cooling.

I see heat exchangers on ebay once in a while. You'll want the 4" model. (the 3" models weren't quite big enough)

If you want to put a V-8 in it, you can certainly do that and the boat will perform spectacularly. You'll need a 1.5:1 ratio drive and you'll need to get all the "stuff' to bolt a V-8 in there including a Y-pipe, bell housing, manifolds, risers, side-engine mounts and all the marine "stuff" you mentioned.

Your best bet would be to find a rotten boat with the engine and drive you want and swap the entire mess and then part-out the 3.7L engine and accy's....... Or just fix what you have and chalk it up to inexperience (buying a boat) most of us have "been-there"/"done-that" so don't feel bad!
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

Thanks HT im just lost on this one...i really like the boat and i think it will be a good boat but ive just got to get this problem worked out....all my other boats have been v8 and didnt think nothing about this one...
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: NEED HELP ABOUT 3.7 Mercruiser?

wkentucky57 said:
Thanks HT im just lost on this one...i really like the boat and i think it will be a good boat but ive just got to get this problem worked out....all my other boats have been v8 and didnt think nothing about this one...
Click to expand...

It's really an uphill battle with the 3.7L engine even if everything is "right" (do a search for all the issues) . Your not having all the "parts" on yours will make it a little "steeper" hill.......

The good thing is there's still a fair amount of people out there with them and if you do decide to swap the entire mess for either a V-6 or V-8, aside from having to do a little fiberglass work adding the side engine mounts (if they're not already there) all your engine parts are fairly valuable. The drive which is ratio'd for the 3.7 is also fairly valuable too. SO, if you don't count your labor (it's "therapy", right?) You can usually make it work especially if you find a rotten boat with the right good engine and drive.

Good luck,


Rick
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

im going to try and get the 3.7 to where it will WORK for now and keep my eyes open for a V8 swap boat...i found a cobra 5.7 but what i have found out that i would have to find a cobra outdrive and not a mercruiser right?
 
H

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: NEED HELP ABOUT 3.7 Mercruiser?

wkentucky57 said:
im going to try and get the 3.7 to where it will WORK for now and keep my eyes open for a V8 swap boat...i found a cobra 5.7 but what i have found out that i would have to find a cobra outdrive and not a mercruiser right?
Click to expand...
Um...........Run fast from any boat that the letters "OMC" any place in the ad,...............
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

ok thanks...thats what i was wanting to know,,,dont need to make another mistake on this boat
 
W

wkentucky57

Cadet
Joined
Aug 13, 2012
Messages
10
Re: NEED HELP ABOUT 3.7 Mercruiser?

NEED to know some more about tradeing motors....have had a guy wanting to sell me a 302 ford mecruiser will it fit the transit thats in my boat now....and what about the cables what will i need to change for the V-8 from the 3.7?
 
You must log in or register to reply here.
Top