92 Yamaha 4.3 V6 Exhaust Manifolds and Engine Block

[Pobuda27]

Just found out my exhaust manifolds on my Yamaha 4.3 V6 cracked over the extremely long and cold winter here in Minnesota. Question is - how do you know if the engine block is damaged as well? Other than milky oil how can you tell? Can't run the motor as I have removed the manifolds already. Take it in and have compression test done? If cracked what are my options? I luckily found a pair of used manifolds/risers here in MN, so if block is OK I think I am back in business. Please help, your advice and recommendations are appreciated. Thanks

 

[Bondo]

Re: 92 Yamaha 4.3 V6 Exhaust Manifolds and Engine Block

Just found out my exhaust manifolds on my Yamaha 4.3 V6 cracked over the extremely long and cold winter here in Minnesota. Question is - how do you know if the engine block is damaged as well? Other than milky oil how can you tell? Can't run the motor as I have removed the manifolds already. Take it in and have compression test done? If cracked what are my options? I luckily found a pair of used manifolds/risers here in MN, so if block is OK I think I am back in business. Please help, your advice and recommendations are appreciated. Thanks

Ayuh,... Welcome Aboard,...

A compression test won't tell ya if the block is cracked, only the condition of the cylinders, rings, 'n valves...

Ya need to isolate the block's cooling passages, by whatever means necessary, then pressurize to 15psi...
If the block is cracked,... You Hear the excapin' air...
The block will need to be Drained to do this test....

Probably shoulda Drained it last fall, 'n ya wouldn't be in this position...

 

[HT32BSX115]

Re: 92 Yamaha 4.3 V6 Exhaust Manifolds and Engine Block

I luckily found a pair of used manifolds/risers here in MN, so if block is OK I think I am back in business. Please help, your advice and recommendations are appreciated. Thanks

I would say your block is NOT OK. The manifolds cracked because there was water in them and it froze.

GM blocks frequently crack "in the valley". you'll see the cracks when you remove the intake manifold.

If you want to verify, isolate the block , heads and intake manifold from the manifolds(which you've already done.....) and risers and pressurize. If it holds air, (15psi or so the block and is NOT cracked.


If your block IS cracked, then you're "done".

My suggestion would be to find a donor boat with a Mercruiser 4.3L engine and Alpha 1 drive and swap the entire mess.

You can part out the Yamaha stuff to the few people out there in radio land that still have them......


Sorry about that!


Rick

 

[Pobuda27]

Re: 92 Yamaha 4.3 V6 Exhaust Manifolds and Engine Block

Thanks for the input gentlemen. I am a newb when it come to this stuff. Reached out to Capt Ken and he said if the "casting plugs" are not pushed out the block probably OK. Where do I look for those on the block?

Rick, when you say "in the valley" what are you referring to? The bottom side of the exhaust holes?

I am going back up to the cabin next weekend to check it out. Cross my fingers as I will try to pressurize and see if air is leaking. Not sure how I will attempt. Will drain block, plug 5 of the exhaust ports somehow and then force air thru the 6th? Any suggestions?

If I were to put the manifolds back on and run it what should I be looking and/or listening for?

 

[HT32BSX115]

Re: 92 Yamaha 4.3 V6 Exhaust Manifolds and Engine Block

if the "casting plugs" are not pushed out the block probably OK

Well, at least he didn't call them "Freeze Plugs" (but still thinks they save you somehow!!!!)

Those are CORE plugs in the block to close hole required for the casting process. They sometimes get pushed out by expanding (freezing) water.

Sometimes they don't "push" out, but the block cracks just the same.

when you say "in the valley"

That would be the area under the intake manifold sometimes called the "Lifter Valley"

The water jacket is fairly thin in that area as it is on the outside of the block (sides) where the core plugs are......

Will drain block, plug 5 of the exhaust ports somehow and then force air thru the 6th? Any suggestions?

You want to pressurize the cooling system. You do that by plugging off the water input and output ports using hose, (plumbing type) PVC pipe fittings. Use a 15 PSI or higher gage available at any auto parts store and what ever fittings you can scrounge to hook it all together.

You can remove the manifolds and risers or leave them on but you just disconnect the cooling water connections to isolate them.....

 

[ebbtide1991]

Re: 92 Yamaha 4.3 V6 Exhaust Manifolds and Engine Block

Got a great deal on a Ebbtide and yammie 2 years ago with cracked manifolds and block (in the valley). Got a local weder to weld manifolds with I think low nickle rod and I ground out crack in block to a "V" and put JB weld on it( 3 coats). I now have 68 hrs on repairs in 2 summers with no leak and or temp issues. Maybe Im lucky but they can be fixed. I also have bought numerous parts off ebay ( manifolds, risers , trim pump and coils for future. I spent around 750.00 total on parts. Insurance I guess. I love my boat and guess i got lucky.

 

[snwbrdingbill]

Re: 92 Yamaha 4.3 V6 Exhaust Manifolds and Engine Block

If your block IS cracked, then you're "done".

My suggestion would be to find a donor boat with a Mercruiser 4.3L engine and Alpha 1 drive and swap the entire mess.

You can part out the Yamaha stuff to the few people out there in radio land that still have them......



Rick

Is this an easy swap? I have a 1993 Rinker 206 with a cracked block and two cracked cylinders. It is currently a Yamaha 4.3. Can I swap with a 5.0 or 4.3 Merc? Any advice would be great. Thanks