4.3 v6 manifold help

boomersooner28 · Mar 8, 2011

i have just moved to florida and caught the boating bug after going out with father-in-law past few weekends. been around boats all my life and this is where its at. so i found a good deal on a gorgeous 86' four winns with a mercruiser 4.3 205 alpha one. i bought the boat knowing it needed manifolds and i am somewhat handy so want to do most the work myself. i took off both manifolds and risers today and yes they were both cracked. so before i go out spending good money on new manifolds and slapping them on an engine i dont know what kind of shape the rest is in.... what should be my next step. should i try and and turn it over by hand and make sure its not froze up, and if not then pressure test??? and how do i go about all this? and by the way i have learned more on these forums than i think i could have anywhere else you guys are extremely helpful and knowledgable.. thanks corey in florida

Black as · Mar 8, 2011

Re: 4.3 v6 manifold help

Dont take this the wrong way but why buy a boat without testing it out in the water first, because if you say it has cracked manifolds I dare say you will have other issues.

boomersooner28 · Mar 8, 2011

Re: 4.3 v6 manifold help

i took this boat on knowing it was going to be a project and need engine work. the hull/floors/interior are nice on this boat. i got a good deal on it and it wasnt the first boat i saw i bought kinda thing. little money and time into this engine is something i am ready for and now its just finding good deals on parts and helpful knowledge. plus its tricky to "test a boat on water" without it running and no not taking it the wrong way. i just new what i was getting into and wanted to bring her back. i guess my question to ya would be whats the next step in finding these other problems?

Black as · Mar 8, 2011

Re: 4.3 v6 manifold help

Sounds like you had a plan...........I would start with a compression test on each cylinder.

boomersooner28 · Mar 8, 2011

Re: 4.3 v6 manifold help

excellent thanks for that black.

BossHogg · Mar 9, 2011

Re: 4.3 v6 manifold help

I agree with the compression test. If you need any tools for the outdrive look me up as I am in Pcola and may be able to save you some money as I just dropped a truckload.

Don S · Mar 9, 2011

Re: 4.3 v6 manifold help

If this engine has been setting a while, you need to at least start it up before even attempting a compression test. Compression tests are never accurate on engines that have set for a while.
As an example, had a 305 engine that sat in the shop over the winter. Blocked it up to run it, did a compression test first. all cylinders less than 100 and 2 cylinders with 30 psi or less.
Started engine and ran for 15 seconds just to see if it ran. Rechecked compression, all cylinders 110 to 130.
I would say start it up and see if it runs, hook up some water and see if you have any big external cracks on the block. You will only need to run it about 30 seconds or less to know. If no external water leaks, then you may have a good engine. Block off the manifolds and pressure check the blocks cooling system, if it will hold 10 psi, then the block isn't cracked. Now do a compression test, since it ran a bit, the test will mean something.

boomersooner28 · Mar 9, 2011

Re: 4.3 v6 manifold help

Oracle so u suggest go ahead and buy some new manifolds and risers for the motor,change the oil and get all the fluids right. Was also wondering if i could save some money by running it by a mech and seeing what he thinks before i dump money on manifolds for an engine that possibly could be junk??? also whats the best place to get manifolds and risers from?

Don S · Mar 9, 2011

Re: 4.3 v6 manifold help

No, I am not suggesting buying anything. Run the engine first, even if you have to run it without water. 15 to 20 seconds of running will not hurt anything but the impeller. Then do a pressure check of the cooling system to check the block for cracks. Then do a compression test. Even a leakdown if necessary.
If everything passes, then you will know where to start on parts buying. Don't even worry about where to buy things yet. There is a long way to go before that's an option.

Don S · Mar 9, 2011

Re: 4.3 v6 manifold help

One other thing you need to do before you start the engine. Remove the outdrive. might as well know the condition inside the bellows before buying parts.

boomersooner28 · Mar 9, 2011

Re: 4.3 v6 manifold help

ok can do that don, i figured i should go thru everything with a fine tooth comb. may sound dumb but do i need to reapply the manifolds i took off to fire it up for the few seconds your talking about? and would trying to turn the the crank by hand first be a good idea to see if the thing is seized up? by the way u have been much help.

Don S · Mar 9, 2011

Re: 4.3 v6 manifold help

You might want to just stick them back on with a couple of bolts, just to keep the flames from the exhaust in check in that enclosed area. Make sure it's open to the air and you have to gas leaks. Low rpm is all that's needed, maybe 1500 max to keep it running.

boomersooner28 · Mar 9, 2011

Re: 4.3 v6 manifold help

will do and i appreciate your time on this!

achris · Mar 9, 2011

Re: 4.3 v6 manifold help

Don't run water through the manifolds. If they are cracked, that water will find it's way into the crankcase and then you'll have the beloved milkshake to deal with. I'd run the engine without the manifolds on at all. Just wear some ear protection.

Black as · Mar 9, 2011

Re: 4.3 v6 manifold help

I agree with achris, better to be safe than end up with more problems.

4.3 v6 manifold help

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