3.7 mercruiser push rod questions

[Erie88renken]

1988 renken classic
3.7 mercruiser with alpha one model 165, 2 barrel carb.

Im trying to get this boat in the water. I have been using this forum nonstop. Mostly I find the answers to my questions by searching the forum. Thank you.

I find conflicting info on my next question which is why im posting it now.

I took the valve cover off to insure all my valves were working properly (not stuck).
I noticed a few of my rocker arms seemed loose. They jiggled around a little. most did not. I turned the engine over by hand and they stayed loose no matter the stroke. The bolts are to correct torque. I took the rocker arms off and pulled the push rods. They all looked fine. ( kept them in right order/position). I rolled each one on glass to verify they are strait and a few are not. Decided to replace them all because they are a cheap part. This is where I get lost.

I can punch in 470 merc pushrods and get a set of the interweb. They are all the same size.

?OVERALL LENGTH: 8.647"
?TUBING SIZE: 5/16" X .060" (stock)
?ENDS: 5/16" Ball

This is the most common size I find.


But then I find sets that are multiple colors and multiple lengths from merc....why.
I also find mixed info on this forum. I have seen people say you have to measure each one and I have seen people say they were fine with the replacements from the web. Also, I hear people talk about a valve clearance tool? What is it? I assume its to measure the gap between the valve and rocker arm, but I have always used a feeler gauge for that.

If you have the time, please explain.


A little more info....bought boat 2 years ago. Had sat for 2 years. I started to mess with it, ended up rewiring dash and most of boat. Finished that in November. January of that year I was shot by accident in the knee and was unable to work on it for next year.
Couple weeks ago I started working on it. Replaced starter, battery, cables, points, condenser, coil, carb rebuilt.
Now I try to start and it just cranks. After I had carb off and back on it at least choked a few times. I don't understand why it wont start. Would bent pushrods keep it from starting? I just got back to do a compression test. I think I did one before I got it and they were all in low 140. Is it safe to keep cranking on it with bent rods? Only want to do it to test compressuion, but I am thinking bent rods would skew results. Sorry so much info and questions.


Boat....Best Of All Times

 

[stonyloam]

Re: 3.7 mercruiser push rod questions

OK the valve lash on the 470 is set by pushrod length, so a given engine could have several different length pushrods. Number and measure all of your pushrods. If you are lucky they will all be the same. Anyway take the bent ones to your local Ford dealer and have them match them. They are 460 Ford pushrods. Yeah they can be a little loose but should be OK when the lifters get pumped up. Need to check for spark. Pull the center wire out of the cap and lay it next to bare metal on the block, turn it over and see if you get a nice blue spark. Next check the timing. Make sure the carb is getting gas. If your gas has been sitting for a couple of years that could be your problem. Try a temporary gas line unto a container of fresh gas. Compression sounds OK, pushrods should have no effect on the compression. Good luck. Welcome to the "470 Club":facepalm:

 

[achris]

Re: 3.7 mercruiser push rod questions

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

sigh......well. This sucks. Got a new compression gauge. First cylinder I tested....30 psi. Damn it. This really sucks. I stopped right there and have been thinking about it all day. What would kill compression like that. I assume worn rings. before I go tearing this apart is there anything Im missing here?

Im going to use the compression tester on a known good engine in the morning just to make sure its good.

I guess I have more questions.

1. If the rings are worn then is the cylinder worn too? Is it like a car engine that can be bored over, or is it just a ring replacement?

2. Would you rebuild or replace. I can get a rebuilt 470 for $2500. I think the rebuild kit is much cheaper.

3. At this point I assume Im going to rebuild it. How the hell do I get it out? My engine lift wont reach and I have no tree to chain it to to chain hoist it out. If I disassemble it can I get it out piece by piece? I assume yes to all but the block. It is aluminum so I imagine I could.

4. If Im going to replace rings, what else should I do while apart? Ill get a rebuild kit but sometimes they leave out things that should be replaced.

I guess that's it for now. Today sucks.

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

Im about to order this kit from ebay. Good price? Any other things I should order at the same time? Engine mounts...etc...?

Im going to start a thread for this rebuild. Ill attach pics of every step. Still hate today.

 

[bfjou812]

Re: 3.7 mercruiser push rod questions

Were you able to see the valves on the cylinder that tested @ 30 psi? The reason I ask is usually pushrods don't bend unless they are put in a bind. A valve could be bent and not closing all the way and giving you a bad reading. I would check the valve train first before pulling the motor.Check the timing of the cam also. What was the compression on the other 3 cylinders?

 

[bfjou812]

Re: 3.7 mercruiser push rod questions

Once you get the motor apart you probably would want to check the camshaft and see if it will need the speedi sleeve repair.

 

[dubs283]

Re: 3.7 mercruiser push rod questions

if you are looking at a re-power, try to find a 4.3 V6 (donor boat) - at least you can still use the drive n transom assy

there are some people here who are fans of the 470 but they know em in and out and are willing to deal with their "quirkiness" - they are a great lil engine if running well and maintained

fact is, they no longer make the 470 so parts are further and fewer in between, and not getting cheaper - nother fact is there are GOBS of 4.3 V6's out there and parts a readily available on virtually every street corner

food for thought...

 

[achris]

Re: 3.7 mercruiser push rod questions

... - nother fact is there are GOBS of 4.3 V6's out there and parts a readily available on virtually every street corner....

Parked overnight in fact :facepalm:

 

[dubs283]

Re: 3.7 mercruiser push rod questions

Parked overnight in fact :facepalm:

...please note, iboats boating forum nor do any of their members condone "midnight auto parts"

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

Im just confused now. All 4 cylinders read 30 psi. or damn close to it. Im going to pray to god that this new gauge is messed up. How could all four cylinders be equally bad. I have never seen a motor on a truck do that. Its always one or two cylinders, not all of them.

I have the valve cover off now. Nothing looked out of the norm when turning it over but ill go check closer and get back with results in a few.

What could have made the rod bend other than a bent valve? I was thinking stuck or sticking lifter.

If my new gauge is working and I really do have 30 psi across the board how the hell did it get to that point? I have never seen an engine run under 100psi. If gauge is right, ill pull the head and post some pics to get your thoughts.

answers to questions.

1. I can see the top of the valves with the cover off. I think they are closing all the way but maybe not, maybe that's why lifters are loose. Ill check now.

2. Timing. It is right on. Everything lines up.

3. 4.3 - I have been told not to do it because it will require rebuilding the stringers to handle it.

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

all the valves appear to moving freely. Guess its time to pull the head and have a look at the pistons and cylinders.

1. What is wearing down, the rings or the cylinder walls or both.( never worked on aluminum block.)

2. Can I just replace the rings, or do I need to bore the cylinders over and buy new pistons.

3. Will there be clearance to swap pistons with engine in boat? I assume no. I don't think I can even get the oil pan off in the boat..hope im wrong.

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

Also, when I stick my finger in the plug hole the compression feels week to me. Ill still hook gauge up to my truck and test it, but I think I already know the answer. Im going to sleep on it for now.

 

[funk6294]

Re: 3.7 mercruiser push rod questions

I would be a little suspect of the new gauge if all are reading at 30 psi. You might borrow one from autozone. First things first though before you pull the motor and redo all it. Check to see if you have any valves that are sticky. The bent pushrods as noted before are a sign that something bound up. You may only be into it for a valve job. I would be surprised the rings are totally shot.

 

[Eric 3.7LX Alpha 1]

Re: 3.7 mercruiser push rod questions

Water in the cylinder can bend a pushrod like warm butter, from reversion. Usually #4 on these engines

 

[stonyloam]

Re: 3.7 mercruiser push rod questions

Whoa, chances are it is not the rings. You need to find out what is going on before tearing into the engine. Try another gauge first. Then try squirting a little oil in the cylinder and repeating the test ( if rings the compression will increase). If you were getting 140's before there is no reason to believe the 30's you are getting now. I would not order anything yet. If anything you might have a bad head gasket, but you need to find out for sure. Were the pushrods bent a lot, or just not perfectly straight?

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

I did not notice they were bent until I held two together. Then I rolled them on glass to be sure. Bent, but not bent like I have seen on stuck or bent valves. Found a local place that will do a longblock rebuild for 1900. That's a lot of gas.

Did not get a chance to test gauge on new engine. Ill get to it today.

Also, p.o. said head gasket was replaced in the spring of last season used. never over heated. beginning to think he is full of crap.

pulled carb back off to look inside. I see rust on block. right where block and intake meet. I pulled the plugs and peeked in cylinders. They look normal. # 3 looks like it might have a rust line at the top of the stroke. Hard to tell for sure with this 2 inch screen.

Ill get pics of bent push rods up tonight, and will also squirt some oil in and see if numbers rise. Thank you so much for helping me with this.

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

added few ounces of oil to cylinder 1. psi jumped from 30 to 60. Please advise on what to do. Im still thinking major rebuild, but if you can prove me wrong ill send you some beer and a big thank you.

I might go pull the head...

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions

This just sucks. I have never seen an engine like this before.


this is one of the loose rocker arms...that clearance seems huge.


at first glance this motor does not look bad under the cover

decided to drop the intake manifold to look inside....crap

cylinders 4 ,3 and 2.

 

[Erie88renken]

Re: 3.7 mercruiser push rod questions








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