Man/Riser Inspection/Replacment How to..?

murphini

Petty Officer 2nd Class
Joined
Jun 17, 2004
Messages
116
1989 OMC 302 Ford V8. 650 hours. Man/Risers never been replaced to my knowledge--18 years of freshwater use.... I have owned for 4 years/200 hours, has run great until last week. Been reading all of the recent water intrusion, hydrolocking, cracked mainfold, repair/replace thread etc.

I had the dreaded "dead in water after running fine hydrolock" where after running great, very s-l-o-w cranking, no start/dead in the water, then next day it started right up on first try. I now understand that with cracked mainfold, water can seep into piston(s) when engine is not running, leading to problem described above. Oil level is fine, but looks more amber than dirty/black so I'm changing also. While water is fun to drink and drive a boat on, it doesn't compress in cylinders or lubricate internal engine parts very well...

Here are my next steps--looking for anything else I should do:

1. I have borrowed a compression tester-will be testing over weekend. Understand to remove sparkplugs, ground coil. I'll check/record the cyl readings to see if one (or several) are bad/low and replace plugs in order.

Q: How will I be able to tell by looking at spark plugs if they've had water damage? What will they look like?

Q: Do I need to do this step--or is it just good practice to see if there is anything else to be fixed? Since boat has run very strong since I've owned it, I've never done a compression check.

2. Inspection of Manifold.... Will the mans need to be removed to be visually inspected, or can it be obvious to see crack just by looking while still on engine? Any Hints/Tricks would be appreciated here (I have the CLYMER manual--so I assume I can just bolt off and inspect? )

3. Replacement of mainfold, or man/risers. As luck has it, checked with my shop, then online and the v8 OMC man/risers are on national backorder, so this will be an offseason project. Will the new man/risers also have the flapper--or is that for inboards only?.

4. Pressure testing manifold? If I am planning on replacing, does this need to be done?

5. Finally....Is this a job for a "willing to learn guy/(me)" with a socket set and manual , or is it better to be done by a real mechanic? If this will be a bear, I am ok with writing a check to someone to do.

Your advice/wisdom/counselling sought--and I may actually follow it.
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: Man/Riser Inspection/Replacment How to..?

1989 OMC 302 Ford V8. 650 hours. Man/Risers never been replaced to my knowledge--18 years of freshwater use.... I have owned for 4 years/200 hours, has run great until last week. Been reading all of the recent water intrusion, hydrolocking, cracked mainfold, repair/replace thread etc.

I had the dreaded "dead in water after running fine hydrolock" where after running great, very s-l-o-w cranking, no start/dead in the water, then next day it started right up on first try. I now understand that with cracked mainfold, water can seep into piston(s) when engine is not running, leading to problem described above. Oil level is fine, but looks more amber than dirty/black so I'm changing also. While water is fun to drink and drive a boat on, it doesn't compress in cylinders or lubricate internal engine parts very well...

Here are my next steps--looking for anything else I should do:

1. I have borrowed a compression tester-will be testing over weekend. Understand to remove sparkplugs, ground coil. I'll check/record the cyl readings to see if one (or several) are bad/low and replace plugs in order.

Q: How will I be able to tell by looking at spark plugs if they've had water damage? What will they look like?
Steam cleaned or rusty....
Q: Do I need to do this step--or is it just good practice to see if there is anything else to be fixed? Since boat has run very strong since I've owned it, I've never done a compression check.
It won't hurt & does not take alot of time, & will let ya know what's goin' on....

2. Inspection of Manifold.... Will the mans need to be removed to be visually inspected, or can it be obvious to see crack just by looking while still on engine? Any Hints/Tricks would be appreciated here (I have the CLYMER manual--so I assume I can just bolt off and inspect? )
Pull them off & look for evidence of rust in the exhaust cavity.......
Look at the mating surfaces......

3. Replacement of mainfold, or man/risers. As luck has it, checked with my shop, then online and the v8 OMC man/risers are on national backorder, so this will be an offseason project. Will the new man/risers also have the flapper--or is that for inboards only?.
There are other options, Dennis Moore has universal manifolds /risers that are for the 302......
Look on ebay & call & ask if they will work for OMC.....
The Exhaust shutters are below the mans in the y pipe....

4. Pressure testing manifold? If I am planning on replacing, does this need to be done?
No, if you find water on one side, that really should be enough verification....
Waste o' time, imho.....
You are way overdue for replacement.....

5. Finally....Is this a job for a "willing to learn guy/(me)" with a socket set and manual , or is it better to be done by a real mechanic? If this will be a bear, I am ok with writing a check to someone to do.

Your advice/wisdom/counselling sought--and I may actually follow it.
Easily doable, IMHO......
Save yourself hundreds.....;)
 

Scaaty

Vice Admiral
Joined
May 31, 2004
Messages
5,180
Re: Man/Riser Inspection/Replacment How to..?

Doc pretty well covered it...and give the Mans and related the float test. And contact (search) fredwerner1 at Ebay..he has knowledge up the wahoo, and Mans at a great price shipped
 

Reel Poor

Vice Admiral
Joined
Jan 29, 2005
Messages
5,522
Re: Man/Riser Inspection/Replacment How to..?

...and give the Mans and related the float test.

This float test you keep mentioning, should it be done with new manifolds to see if they're cracked from shipping or faulty castings? Will they float if they are good? :p
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: Man/Riser Inspection/Replacment How to..?

What is a 'float test' and how is it done?
Take off the manifolds & risers & throw 'em in the water.....
If they float, put 'em back on....
If they sink.....
Leave 'em.......;)
 

murphini

Petty Officer 2nd Class
Joined
Jun 17, 2004
Messages
116
Re: Man/Riser Inspection/Replacment How/ Update

Re: Man/Riser Inspection/Replacment How/ Update

Plot gets thicker:
1. Float test--dumb question--throwing in water sounds like the old "Snipe Hunt" trick. Not sure I understand how or why they would float or sink. Do you need to plug the holes first--or more on why floating shows good and sinking is bad.

2. Mainfolds for an OMC FORD 302.... having hard time finding the old log style for FORD anywhere. So I would need the newer Center Rise mainfolds--but how does that link up with the existing y Pipe?

I found a conversion kit at Go2Marine that supposedly will convert FORD log/rear to new center with an elbow kit.

BUT FIRST...I'm going to do the compression check to see if it's a blown head gasket.

Then take off the Mans/Risers to look at the flapper and do the so called "float test".

And as DonS says, I need to find fix my own problem first before throwing parts at it.
 

HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
Messages
10,083
Re: Man/Riser Inspection/Replacment How to..?

Ok......back to reality...


Fresh water sitting in areas that don't drain will eventually cause rust thru.

Fresh water sitting inside a manifold (in the water jacket) increases the humidity all thru the water jacket increasing the corrosion.

In time they rust thru.

One of the first places for rust to propagate is in the mating surfaces between the riser/elbows and the manifold. This is why they should be checked and gaskets replaced every 3-5 years in fresh water and maybe every couple of years when salt water goes thru the manifolds. (Raw water always flows thru the exhaust elbows) Someone posted the manuf suggested intervals here some time ago......


It's unlikely that you have a blown head gasket but it's of course, always possible and as old as the engine is a comp check is never a bad idea if you think you have a problem.

Swapping out the manifolds and riser/elbows is not a hard job for most people who can change a water pump etc.

Your manifolds are 18 years old. REPLACE THEM! It just not worth waiting for them to start leaking. Pressure checks will only determine IF they are leaking......not WHEN they will start leaking! It's a gamble if you wait to replace them when they start leaking.....You might find out after it sits for a whole winter....then you'll replace the whole engine.

You should absolutely get the "new" center riser kits. stay with stuff that is still being made!

Consider yourself VERY lucky that you can still buy new manifolds. If you had a 7.5L/460 OMC like I had in my Four Winns, you would be soo done. There are NO manifolds out there for a 460 (except used and new-old-stock....and no one seems to be able to find many of those either!)



Regards,



Rick
 

oh-u812?

Petty Officer 3rd Class
Joined
May 29, 2006
Messages
76
Re: Man/Riser Inspection/Replacment How to..?

I'm pretty sure they telling you to go ahead and order new ones. If your goin through the trouble to remove and they're that old - go ahead and replace.
 
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