83 Nautique 2001 - Mercruiser Chev 350 260 issue

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!

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

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   

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.

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).

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

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.

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

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 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.

If you check this posters location you will see he lives in South Africa. What is available to us and common may be unobtainable for him.
Gary, lean burn is a common cause of local heating and gasket failure.
Overheating does the same thing. The hottest areas grow the most and crush the gasket.
Fel-Pro offers a nice chart showing how to map a gasket and record the measurements to show what area's have been crushed. Once you do this you know exactly what happened in what cylinders.. It is a nice tool to help search for the failure area.
This is a boat with a raw water pump. Many times we see old impeller pieces lodged far inside an engine blocking water flow. Worth ruling out before the new parts install.
It is horrible to do all this work and have the exact same failure again because the cause was not identified.
Mark

For those interested the area on the block where the valve seats was really badly pitted, even I could tell they were looking horrible after they had cleaned up the head.

Mark would that be caused by running lean? It looks like with the Chevy design with the two exhaust valves being next to each other could cause trouble, It also looks like the sealing surface between the two cylinders on a Chevy is thinner compared to a Ford too. Now I have to find a pic of a Chrysler head to see their take

Just going to throw one thought out there.

You mentioned above that when you were removing your exhaust manifolds, that at least one of the bolts was already loose.

Is there any chance that this slight knocking you hear was an exhaust manifold leak?

geecee wrote: He suggested I get it skimmed and the valves etc checked by an engineering shop and put it all back together..

Skim cut like he said and grind valves and seats. New valve seals and put them back on.
Note: I said "them".   Do both heads