'87 Mercruiser 3.7 Engine Noise

[ewpvic]

Finally did a quick sea trial today, but the engine started making a loud tapping sound (like the clacking of the fuel pump arm being hit by the cam shaft). Got louder as I throttled up.

Is there a chance that I did something wrong on the fuel pump install or could it be detonation? I immediately spun around and headed in to the dock. Don't want to ruin this cool little engine.

It also felt like it came out of the hole VERY sluggish.

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

Update. I CANNOT get the engine to make the noise when it's on ear muffs. Even putting it in gear. Sounds like it's running the way it should. Stator noise?

Please help.

 

[stonyloam]

Re: '87 Mercruiser 3.7 Engine Noise

If you just installed a new pump, there have been some folks that have had trouble because of the thickness of the fuel pump gasket. The thinner gasket causes problems because the fuel pump lever is too close and puts too much pressure on the cam. If you have the old pump and gasket, check the thickness and fuel pump lever length and angle. good luck.

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

So is there any secret to installing the fuel pump? If so, I missed it. I mean, it's just bolt up and go right?

 

[stonyloam]

Re: '87 Mercruiser 3.7 Engine Noise

Don't know if this is your problem, but read this: Discussion Forum: New fuel pump - use spacer, or not?

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

Finally got a compression check -

1 - 130
2 - 135
3 - 128
4 - 130

This was cold.

Re-installed the fuel pump with the ORIGINAL gasket. Still not making the noise while in the driveway. I will take a video at the dock as soon as the weather clears up.

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

Well, no need for video. Noise is gone. Boat performed almost flawlessly. I guess it DID have something to do with that new pump gasket.

 

[Eric 3.7LX Alpha 1]

Re: '87 Mercruiser 3.7 Engine Noise

How did it feel out of the hole?

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

Like it's supposed to. Got on plane so well, that I didn't even fell the need to trim the OD. The hull DOES list to the port side a bunch. No trim tabs. I'm going to take the foil off today and see what happens.

Temp gauge showed that it ran much hotter in upper rpm range, but I am going to check with digital temp before I get too worried. Engine didn't "smell" or feel hot.

 

[stonyloam]

Re: '87 Mercruiser 3.7 Engine Noise

Temp gauge showed that it ran much hotter in upper rpm range, but I am going to check with digital temp before I get too worried. Engine didn't "smell" or feel hot.

Want to keep an eye on that, should run about the same at all RPM's. If it cools back down when you go slower should do some investigation. Cruised with mine for a while this weekend, then went WOT for about 5 min, the temp was steady. One thing to check is that the water flows freely out of the exhaust elbow, a restriction there can cause reduced flow through the exchanger. Glad she's running well, I like mine better all the time.

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

I will, Terry. Gonna give it a good running today then open up the valve cover, recheck compression etc, etc. Can't hurt.

Is there an easy way/tutorial on here on how I can determine the flow through the bellows. It seems to be flowing well on muffs.

Heck, I only have about $900 in this boat to begin with. I love to tinker.

 

[stonyloam]

Re: '87 Mercruiser 3.7 Engine Noise

Is there an easy way/tutorial on here on how I can determine the flow through the bellows. It seems to be flowing well on muffs.

Of course not you just gotta wing it with a 470 LOL. What I would do is remove the aft hose from the heat exchanger that goes to the exhaust elbow water outlet and attach a garden host, turn it on full. The water should flow through the elbow and out of the outdrive with little backpressure. The other thing that you can check, is remove the front cover from the exchanger (only raw water will come out) and make sure that the tubes are clear. The starboard set of tubes are the inlet and most likely to accumulate stuff blocking them (old impeller parts ect.).

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

10-4.

OK, so I have the original Medallion gauges. The temp gauge got to what would be ~175-185, and never really moved. Would an older gauge be that far off from the true temp (without using a digital to check it yet)? It never felt like it was running hot. I'm definitely going to compare actual to the gauge tomorrow.

Man, this little engine is starting to wake up and RUN! I ran about 33-36 (gauge) with wife and two kids today and still had a bunch of throttle. I don't like to run WOT. Good enough for me!

 

[Eric 3.7LX Alpha 1]

Re: '87 Mercruiser 3.7 Engine Noise

That 33-36... is that MPH or RPM?

That's the 4.36" holes you have in the block that the pistons ride in

Big bore and torque.. and very good on fuel.

 

[stonyloam]

Re: '87 Mercruiser 3.7 Engine Noise

10-4.

OK, so I have the original Medallion gauges. The temp gauge got to what would be ~175-185, and never really moved. Would an older gauge be that far off from the true temp (without using a digital to check it yet)? It never felt like it was running hot. I'm definitely going to compare actual to the gauge tomorrow.

Man, this little engine is starting to wake up and RUN! I ran about 33-36 (gauge) with wife and two kids today and still had a bunch of throttle. I don't like to run WOT. Good enough for me!

My gauge has never read right, it goes up to about 140 and holds steady there. I keep an eye on it, and as long as it doesn't start creeping up I consider it good. Yeah it is a pretty good engine, as long as you take care of it it should serve you well. Welcome to the "470 club":facepalm:

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

Eric -

That's MPH......2 adults, 2 kids and a bunch of party gear (full cooler, etc, etc). I'm still getting a pinging noise above 3000-3400. I'm trying to see if it's gas or if I missed the timing.

 

[ewpvic]

Re: '87 Mercruiser 3.7 Engine Noise

Word to the wise, newbies (especially 470 owners):

Read the posts that relate to your problems, listen to the elders' as they give you advice/coaching.

Just got back from a GREAT night cruise to a restaurant that a friend owns. Narrowed down my engine problem to either gas or timing (by listening/reading). Reset the timing - BINGO!!!! NO noise in upper rpms. Boat ran great - 2 adults, 3 kids - 40 mph GPS, WOT. Like a TOP.

Big ***** smile. Doing it again in the morning.

Thanks to all the great people that make this site the best place to learn and understand your engine.

 

[stonyloam]

Re: '87 Mercruiser 3.7 Engine Noise

Congratulations!! One last thing on gas. Use regular NON-ETHANOL gas if you can find it, will make it run even better.