Mercruiser 2.5L replacement exhaust manifold to elbow fitment question

[AgnotGt]

Hello everyone

Yes, this is my first post. Thanks for this forum! New boat, 87 Glastron Conroy X-16, haven't even had her in the water yet.... I did search but still need help. I thought I had done my research but what I have is wrong and there must be a correct answer.

1987 Mercruiser 2.5L (B731139)
w/Mercarb 2 x 3 11/16 base
5 bolt manifold (casting #42673 C1)
one piece elbow (round)

Cracked manifold found; ordered new 860235A04. It has smaller intake ports but the real problem is that the mounting pad for the elbow is longer and has 4 water ports (old one had three) and the elbow base doesn't cover the pad to seal.

Do I have the wrong manifold (my guess) or do I need to make an adapter plate to seal the rear hole?

Here are pics of what I am working with. Thanks for any and all suggestions! Glenn

Fingers crossed / wallet hidden :facepalm:

.

 

[Silly Seville]

Re: Mercruiser 2.5L replacement ehaust manifold to elbow fitment question

Re: Mercruiser 2.5L replacement ehaust manifold to elbow fitment question

5 bolt manifold 99798A9 (casting #42673 C1)

Cracked manifold found; ordered new 860235A04. It has smaller intake ports but the real problem is that the mounting pad for the elbow is longer and has 4 water ports (old one had three) and the elbow base doesn't cover the pad to seal.

Do I have the wrong manifold (my guess) or do I need to make an adapter plate to seal the rear hole?

Yep...wrong manifold. I have the exact same manifold as your original from an '88 3.0 liter. Hope you can send that one back for a refund, or you will be changing the elbow to accommodate the new manifold.


Determining the Correct 3.0L Mercruiser Exhaust Manifold | Performance Product Technologies

 

[AgnotGt]

Re: Mercruiser 2.5L replacement exhaust manifold to elbow fitment question

Yep...wrong manifold. I have the exact same manifold as your original from an '88 3.0 liter. Hope you can send that one back for a refund, or you will be changing the elbow to accommodate the new manifold.

You called it!

Thanks for prompting me to do more research! That lead me to find out the following....

The manifold that most offer is the 860235A04 which is the newer design. Smaller ports and the different elbow mounting pad. They expect you to buy a new elbow (part #12076A2) which adds about $250 or so to your repair bill. Soooo...

I spoke to Dave at Barr Marine and they have the correct "direct replacement" for a reasonable price; list $254.55 plus shipping. (Part number MC-1-99798) Large port and proper elbow pad. Not bad! They had me order thru: Inboard Online Boat Parts

The original manifold I ordered WAS wrong for my app and they are sending me an RMA. ( I had given them my serial number and ordered based on them confirming it was right for my motor. )

Other than losing a couple of weeks time I should be good to go; soon.

Thanks again! Glenn

.

 

[Fishermark]

Re: Mercruiser 2.5L replacement exhaust manifold to elbow fitment question

A good tip - if it comes with a green paper gasket for use between the manifold and elbow, throw it away. Buy a genuine Quicksilver graphite gasket. MUCH better.

 

[AgnotGt]

Re: Mercruiser 2.5L replacement exhaust manifold to elbow fitment question

A good tip - if it comes with a green paper gasket for use between the manifold and elbow, throw it away. Buy a genuine Quicksilver graphite gasket. MUCH better.

One of the reasons I bought this boat was that it just had the upper end and service done; over $2500 in receipts. There was a new graphite "colored" gasket at the elbow. It was destroyed during separation because it was also glued on with something strong. Almost clear from what little was showing. Spent 1/2 hour just scraping the elbow side clean.

Haven't received the tracking number yet but I hope to get the replacement manifold early next week.

Thanks for the suggestion; I'll call and ask what type is supplied. Then I can order one now if needed. Glenn

.

 

[Silly Seville]

Re: Mercruiser 2.5L replacement exhaust manifold to elbow fitment question

A good tip - if it comes with a green paper gasket for use between the manifold and elbow, throw it away. Buy a genuine Quicksilver graphite gasket. MUCH better.

+1 ^^^^^

This is absolutely critical! DO NOT under any circumstances, use the cheap green paper gaskets to mate the elbow to the manifold. ONLY use the genuine Mercruiser/Quicksilver gasket. Those graphite gaskets are crazy expensive, but man do they seal! They are obviously a one-time use product, and they are incredibly sticky/gooey/ once compressed. That is why you had a difficult time cleaning the previous one off.

I highly recommend you check both mating surfaces on the manifold/elbow for perfect flatness before you make the final assembly. Have a machine shop check since they have the tools. It is not unheard of for a brand new manifold to have less than ideal surfaces to start with. And unless you know for certain that your elbow flange is perfectly clean and flat, you will have problems. The last thing you need is water in the engine where it doesn't belong...like the cylinders!

Good luck!

 

[AgnotGt]

Re: Mercruiser 2.5L replacement exhaust manifold to elbow fitment question

Thanks for the "heads-up" on the green gaskets. I ended up with all graphite but the manifold shipped from Barr's came with a green intake; I now have it as a "emergency spare".

Real pleased with the Barr's manifold; as far as the "casting and machining" goes. Not so happy with the paint; it was however easy to clean off the matting surfaces. Just a little carb spray....

This manifold was the SIX bolt version. Barr's told me it would work exactly as the oem (5 bolts for mine) but the head was setup for six so "good to go"!

Ended up using Permatex Aviation "form-a-gasket" instead of "Quicksilver Perfect Seal" so we will see how that goes.... Both made by the same company.

The seller covered me for the manifold and so I headed out for the water! Hold it not so fast son... We have a "Zebra Mussels" problem in Calif so I prepped the boat as per their website; clean and dry! BUT hidden three layers deep is the important knowledge that you also NEEDED to have owned the vessel for 30 DAYS prior to your arrival at the ramp (s) of your choice. 150 miles of driving 30 bucks in gas and the frustration of "not knowing" I needed more than just the registration, in my name, for both the boat and trailer! I was 4 days short of the magical 30 days!:blue::facepalm: I understand both policies just wish DMV had given a warning or a more "important'' title on the lakes website or even when I called.

So I hope to put her into the water soon but now it looks like ocean (Santa Cruz bay) instead of lake for her first and last outing before winter. Planning on hosing her down good with Salt-Away and giving her fresh bearings and new bunks before winterizing along with another new (to me) product Fluid-Film. Hoping to prevent major moisture issues where I live (anything metal sweats here). This product is wax based and looks like it keeps the moisture from getting to the protected surface, we'll see.

So thank you both/all for the support!

Glenn

 

[AgnotGt]

Re: Mercruiser 2.5L replacement exhaust manifold to elbow fitment question

So just a follow-up. Put her into the water for the first time and she floats! More than that even in choppy water with 2ft swells she came right up on plane and did 4500rpm's at 42mph. No leaks anywhere so I couldn't be happier unless this was the start of summer instead of winter.... For the first time in three years it's going to dip into the 20's in the next few days.:blue:

edit: 25* for 4 days? wow... Hasn't done that or been so low for years! Normally in the 30's here.

Winterized and trailer blocked off the ground I think I am ready. New factory manual should be here tomorrow and I will be replacing the bunks in the spring.

edit: Engine: electric blanket and along with two lights on the outdrive wrapped with insulation then bagged to keep dry.

Put water in bowls. One on the fender & one on the engine cover under the tarp. Fender froze one the 3rd day the other never got ice! :happy: (end 12\16)



.