83 Nautique 2001 - Mercruiser Chev 350 260 issue

Thanks for the insight. My wording perhaps is not 100% here, also I don't know the correct terms as to the areas on the head etc.

The area where the valve seats is badly pitted, engineer used the words badly corroded.
My valves are already the biggest you can buy and there is a tiny bit of movement here, should be okay for now, but any more wear and I will have a bit more of an issue.

Impeller was still in okay nick when I got the boat, it was the first thing I changed in any case (housing and impeller), did find some bits of rubber throughout the cooling, obviously from a previous impeller which I pulled out as best I could.

Motor runs cool when on the water, I always keep an eye on the gauge.

Plugs on 1 and 3 looked semi dry 5 and 7 were wettish. Plug gaps looked pretty consistent all round.

I bought new intake valves today, there was enough meat on the exhaust valves for him to clean up and reuse, the head was getting skimmed when I dropped them off, I should have it all back in the morning.

edit: had a closer look at the head gasket, that part at 3 o'clock on 7 does look a little suspect, has some discolouration on, it has become a bit damaged with me carting it around to get a replacement, so I don't think mic'ing it at this point would lead any useful results.

mark c wrote: You don't want to go out and get a set of Vortec heads (which came out in the mid 90's) with the valve cover bolts down the center and a heart shaped combustion chamber, They require different intake and exhaust manifolds than your normal small block chevy heads.

Mark

If you were to do this you'd probably figure out that the old exhaust manifolds will bolt right on to the 5.7 Vortec heads

Thanks mark 👌🏻
In my general vicinity we have 1 shop that sells V8 spares, they are very knowledgeable and helpful albeit a little pricey but they have the market cornered so that's just business. They did mention doing something to the guides to give them a bit more life, but I can get a 'good' second hand set of heads for about $300 which considering what I just spent on gaskets and valves really seemed reasonable.

Unfortunately here V8 engines aren't as common as over there, and as soon as I mention reverse rotation or marine everyone's faces go blank

Duane in Indy wrote: Don't know all about shipping and import fees but these might be worth looking into. Save 40 or more pounds and wake up that SBC some. Post this number in the E-Bay search line:     291996169160 And for Ford fans, try this one:    351880220666

Not a bad price that, freight is $120 still way cheaper than I have been quoted for a new set here, slightly more than half the price of local supplier.

No differentiation vortec vs non-vortec on SkiDIM's site (they sell Pcm chevy manifolds). Interesting.

Couldn't find anything in an hour searching google re: different exhaust bolt pattern/port alignment with vortec heads. Definitely true on the intakes (sounds like there are some catalog gm vortec heads that offer both intake bolt styles- but the old style intake ports don't align). I'd like to hear more about this, as vortec seems like a good way to go (if you're stuck with chevy power, of course).

TRBenj wrote: I'd like to hear more about this, as vortec seems like a good way to go (if you're stuck with chevy power, of course).

It's a solid upgrade and pretty cheap too. You can find Vortec heads very reasonable out there.
The articles make it seem the reason for the intake change is the new bolt pattern but the Vortec intake ports are much taller than the old version. They flow a ton better over the entire RPM range.
Then the smaller heart shaped swirl ports bump the CR a little.
The one downside is you also need new valve covers as they bolt through the center instead of around the edge. Good and bad thing IMHO. The center bolts seal better and it's much easier to remove the covers if you have to but cosmetically, I still prefer the old style. I'm pretty sure that the new covers are also taller too. Leaves enough room for roller rockers without a problem.
I don't recall for sure if you can reuse the old pushrods. I'm thinking not but I would have to revisit that to verify.

Overall, the end result would easily match what is achieved with GT-40P's and an intake on a SBF. The cost of the upgrade would probably be more than a similar SBF upgrade but only because of the valve covers (and possibly the pushrods) that are needed.

Popped head back on with new gaskets, set the rockers and turned her over, had full compression on all cylinders,

Connected everything back up and fired her up, didnt go, but that was our fault, didnt check ignition timing, fixed that and she fired up and purred, still had a slight tapping sound, but otherwise smooth and idled great.

Headed out this weekend to camp out and took the boat with, did a few runs, the boat seemed to be smoking (white smoke) far more noticeable that I had ever seen, thought it may be oil from assembly so shrugged it off (it had a slight smoke at WOT in the past, but I never run that speed), got the better half up on skis for her first time

Boat developed a small miss at low revs, so we took her out to feel and check perhaps the ignition timing wasn't quite right, temp seemed high, suspected loose wire on the temp transducer, but sorted that and still seemed odd, while i was out felt the gearbox was slipping, so topped up the oil there and soon after I heard a strange almost sucking sound,

Tried to turn her over and no go, pulled plugs and water came out the cylinders
We religiously torque everything to spec and triple checked every bolt, made sure it was all perfect and tightened in the correct sequence over a three stage torque process.

Right now, I am considering picking up a reman merc assembly off ebay, shipping included it may come in cheaper than a local rebuild, and prbably more reliable, also not sure who I could trust locally with a rebuild of this motor, as not many V8s around and also virtually no marine, let alone reverse rotation.

Any other options ?! anyone got a nice low hour engine they can crate and ship me as scrap   

I feel sorry for folks any time the dreaded water in the he motor happens... It's never clear where it got in...You spend time and money only to be frustrated again and back at square one. Well if you are not afraid of being too deep$ in the boat your sanity and joy can be restored with a mercruier complete engine...All new... I got the 350hp 383 stroker and it's been plug and play awesome ever since

So sad to hear that an assembly mistake causes so much agony like this. I cannot imagine the frustration. Makes you want to go find a deep spot and pull the drain plug! Ugh!

1 and 7 had water in, so the outside two, Hearing this I could guess that intake perhaps didn't seal properly, but the motor really felt smooth when we first took her out.

I did put sealer around any areas with water chambers, but maybe it wasn't enough.

I haven't checked the oil again but when we were on the water it was still clean.

Your block could be good for more miles if the heads are fixed.
You may be getting water into the engine through your exhaust if the manifold is going bad.
I made a set up that allowed me to pressurize the cooling system on my brothers boat searching for coolant leaks, I was going to pull the heads. The engine held 35 PSI of pressure for 2 days with no leak so I learned our problem was coming in from outside putting water in the cylinders. You can plug all the exit hoses to seal the engine and make a contraption that allows you to pressurize the engine to see if you have an internal leak.
Both exhaust hose coolant inlets need to be plugged. and pressurize from the coolant inlet where water enters your engine.
Be careful not to use too much pressure, cars run at less than 20 PSI. If you pump it up to 60 psi you might blow out gaskets that are currently good. I think my 35 PSI test was about as high as you should go. I picked up parts for my test at the local hardware store.
I don't have a picture of the boat test but this is on my wifes BMW, same set up I used on the boat.

I was tempted to get new heads, but also worried about throwing more money at the problem without knowing root cause.

Heads would save me a heap, but may not fix the initial reason I looked into the motor,
which was a sound I can only describe as a loose tappet sound, That's when I did comp test and found no compression etc.

In hindsight I should have done both heads together, but was hasty as I wanted to use the boat this weekend just gone. Thinking about this now, if my valves have a bit of play because there was wear on the head by the valve guides, could this also allow excess oil to be burnt off.

If there's no water in the oil your water passages in the manifold are sealed good because if they leaked, the water gets directly into the oil

You could have a crack in the head above the intake or exhaust valve in the #1 and 7 cylinders, leaking head gasket or bad manifolds.

If the machine shop had the valves out, they should have been able to find this. With cracks like this the water leaks into the combustion chamber when the valve is open
.
You said you had lots of white smoke, my guess is that it was steam from the water in those 2 cylinders

What did you use for torque values when you put the head on?

Turning the engine over with no water supply and the plugs out should blow the water out of the cylinders, then squirt some oil in and do it again.

if you test the system like MrMcD said you should be able to locate the issue

yes i worked in nm but made sure to use the correct scale.
and I believe I got the torque ratings from boxwrench.com but checked a few sources and all were pretty much the same values so I picked one that had both ft lb and nm for me to cross reference