Engine rebuild wish list

As I mentioned above, you have to learn about building a marine engine. Read up on all the factors responsible for building torque at low RPM. You can't just buy a cam and put it in though using the factory configuration and parts that came with your engine will be very close. The single biggest difference is the factory 'shim' head gasket that's about .017" thick as opposed to aftermarket head gaskets that average .046" thick. Understanding what the differences mean and how to build around these factors is key along with the different combustion chamber sizes of the heads.

The book I got to learn from is 'Small-Block Chevy MARINE PERFORMANCE' by Dennis Moore. It cost under $20 used back then. Just googled it...quite a shock...

http://www.amazon.com/Small-Block-Chevy-Marine-Performance-Modifications/dp/1557883173

There are other books by other authors on marine engines but I haven't read them so I can't vouch for what they teach.

Here's the Big-block book. slightly better price

http://www.amazon.com/Big-Block-Che...1&keywords=Big-block+chevy+marine+performance
 
I have looked at both new and reman engines. For the price, I can rebuild what I have at a much reduced cost, and still have some to do up grades. So far, after reading the coments, I believe I am pretty well stuck on upgrading the fuel system to fuel injected, and up grading the ignition system, this should give me some fuel savings, as well as a little bolt on HP increase (end goal is not extra power, it is fuel and reliability).

Charlie, believe it or not, I actually do know about the different thickness head gaskets. I have used that on a few racing engines I have built. I had planned on going OEM on at least the head gaskets for this very reason. The industrial version of the gm 454 used the same as the Marine. Will order the books as well. I havent responded to your comments much because, well I think that is obivous. So keep it comming.

Ok, so scratch the cam unless it is damaged. Wont really know about crank and pistons until I get in there, bearings are a given. Inspect the seats and guides in the heads and if they show no wear, just do the seals. If they look ok, I probably wont have them faced unless I see signs of leaking. Replace the lifters is likely because I know a couple are colapsed. Replace Sensors and sending units since they are cheap and I can get to them, wiring for sure since I know the low oil pressure shut down did not work and I currently dont know why. Replace the starter since I can now see that it actually has a starter (you would think they could have found a better place than on the bottom, really guys the bottom) replace alternator, upgrade the raw water pump, and of course all hoses, lines, belts, etc.

End goal is not a hot rod, end goal is better fuel burn and reliability. I had plenty of power and speed, that was never an issue, but we are still planning an off coast vacation in it and I want to know I can get back. Plus a lot of it is just because I am in there, its a well why not replace it, I have it in my hand, even though it may not need it. So lets say I dont replace something, and a year from now I start haveing an issue, first thought will be, I wonder if that part I did not replace is the cause? Because even though it only has 168 hours, it is still 25 years old, thus the root cause of the failure, old hose.

On another note, should I replace the spline hub since it is out? This is the piece that bolts to the flywheel that goes to the outdrive? This would be more a preventive measure than a requirement.........D.........
 
Just adding another suggestion- Consider a cast alu marine oil pan if it doesn't already have that.
 
I havent hit it with a magnet yet, but I believe it to be carbon steel. I am concidering that and maybe an akuminum intake. The intake would give me a little weight savings and would not have to worry about rust.........D........
 
It would be a shame to do all this work and NOT do a cam upgrade for more power. More power (torque)translates to a little less throttle opening than previous cam. Throttle opening IS where fuel economy lies. The other end of economy is the most efficient prop and gear ratio. This is usually acheived by using the largest diameter prop available turning as slow as the gear ratio allows to reach the recommended WOT. The WOT is where the maximum HP is acheived in the RPM curve. HP is a mathematical equation derived from the torque curve. I never bothered to find out exactly how HP is calculated, but, The HP and torque curve always intersect at 5252 RPM. Here's some google about HP/Torque

https://www.google.com/search?q=HP/....11255j0j7&sourceid=chrome&es_sm=122&ie=UTF-8

Learn about marine cams.

https://www.google.com/search?q=Mar....10456j0j9&sourceid=chrome&es_sm=122&ie=UTF-8

Basically you want to build the most torque at the lowest RPM(with the flattest torque curve), which hopefully coinsides where the most power is needed...bringing the boat on plane. Around 1500- 2500 RPM depending on the boat.

The components of a fuel injected engine may need slightly different cams, pistons or head chamber configurations. I haven't built for a fuel injected engine yet so I don't know.
 
So Charlie, you disagree with the statement of leave the cam be? That is a lot of reading for sure. A new cam is not very expencive, just gotta pick the right one.

I keep hearing that I might have to change pistons and valves if I go fuel injected, which I really dont get. Think about it, it is a 4 barrel throttle body injection, it still delivers an 8 to 1 ratio air to fuel, the other two injectors wont come into play until the throttle is open enough, just like the original carb does. It just keeps a better mix ratio, that really it. Dont see what the valves would care, they just open and close letting it in and sending it out. The pistons, what do they care, they just go up and down. Dont really need any higher compression, the mix is still the same. Just the source of the mix is different. I know people who have done this on thier cars with great success, only thing they say is to run it a little richer than the system wants to. Other than that, it is a straight bolt on.............D.........
 
I w2as thinking MPI. George did some investigating into TBI. All reports say there is no advantage
to TBI since it acts just like a carb. Even with a bunch of sensors, it will only be able to
adjust the fuel/air to the engine as a whole, just like a carb, not to each individual cylinder
like MPI where each cylinder has it's own injector. He convinced me to stick with a carbed motor.

As far as pistons go it may depend on the shape of the crown of the piston. There's a lot of information
for you in the books. Thinking a piston is a piston and a valve is a valve and a head is a head will
likely get you in trouble.

A little story. On my first marine engine build ( Pre GVP), I used a machinist That has been building auto
engines for decades. I knew there was a difference between auto and marine but I thought it mostly depended
on the SS head gasket and brass freeze plugs and marine type cam. I asked specifically if he knew how to
build a marine engine and he said sure. Turns out he had no idea what a marine engine went thru.
Neither did I for that matter.
Shortly after break-in (no hot rodding) I started loosing power. Finally I pulled the engine and started
dismantling. Just got as far as the heads to find out the exhaust valves sucked into the heads.
What happens is the constant load a marine engine is always under creates an extremely hot combustion
chamber. All the hot gasses heat the exhaust valves red hot which also gets the valve seats red hot
and which makes them soft so all the pounding they take pushed the valve seats up into the head.
Had to have hardened seats installed. There's a little more to it but it all comes down to the
increased combustion temps from constant load and how to counter it.
 
You may want to check out some of the performance forums. There are many threads on rebuilding BBC. Also on fuel injection. Just do some searches and you will have plenty of reading.

One of the best marine engine builders used to be in Mississippi but now is in Nashville TN. Eddie Young of Young Performance
 
Charlie, I did not mean to say that valves are valves and pistons are pistons, it is just in this case, just changing a 4b carb to 4b tbi, I should not have to change pistons and valves. In the case of mpi, you have to have different pistons. And it is hard for me to believe there is no advantage going to tbi, I know several people who did this conversion on thier engine and claim much improved fuel econ and increased HP, as well as easier starts and smoother overall running.

Got the bottom of the engine room degreased and put the first coat of paint on yesterday, going to continue this today. Makes a huge difference in the way it looks for sure. And yes, there will be before and after pictures......D.........
 
Most people that went to TBI were probably having problems or didn't know much about their carbs in the first place. That's probably why they claimed such improvements. There's be a 100 fold difference listening to their claims and what GVP told us here. Of course, if you have your heart set on a TBI...
 
Wellll, I wouldnt say it is set, it is a 2800.00 upgrade, lol. Was not having issues with the fuel system, just looking for better fuel econ, marine gas is expencive you know. If I were to go mpi, this might as well mean a new engine, dont think I need that. Sure dont need the cost........D.......
 
What type of drive system do you have? What size and weight is the boat?

Sounds like you have plenty of power but want to get better mileage. What's you MPG now?
I do mileage by Miles Per Gallon rather than Gallons per Hour. Been doing it that way for
over 50 years so it's what I'm most familiar with.

I've done extensive work on my boat all to get better mileage. I've bumped my torque up
and up over the course of 10+ years, sometimes rebuilding my engine 3 times in 2 years
trying to hit the right sweet spot. Finally George suggested a BII outdrive with it's large
selection prop diameters up to 22" and gear ratios of 2:1 and 2.2:1. That hit the nail on
the head. HP/torque increases raised my mileage about 10%, The gear ratio and prop diameter
increased an additional 20% alone. It's good to have someone like GVP with the knowledge to
help you out. It also helped out with the holes in my wall and the soft spot on my forehead.
 
What type of drive system do you have? What size and weight is the boat?

It has a Bravo I with factory SS prop. Boat is 33', and she is heavy. I havent took it across the scales yet so I do not know the exact weight, but it is heavy. Had the marina put it in for me once with thier tractor and they would not do it again, said it was too heavy for them to safely pull. Which is fine as my ford has no issue doing it, other than having to get so far in the water with the read end.

Sounds like you have plenty of power but want to get better mileage. What's you MPG now?
I do mileage by Miles Per Gallon rather than Gallons per Hour. Been doing it that way for
over 50 years so it's what I'm most familiar with.

Power never really has been a problem, but fuel burn, jeeze. I havent measured it via mpg yet, but I pulled the family around on the tube for a couple hours, and just a couple, 275.00 bucks later I toped the tank back off. Need a little better than that.

Swapping the outdrive is a viable option, but I dont have to pull the engine for that. Looking at stuff I can do since the engine is out. Drive is mint other than needing new paint, so I am not ready to trade that out just yet. With that neat little jack of yours I copied, the drive is off in ten minutes, so easy......D.........
 
The BII is made for heavy boats and house boats. The large props also creates a
lot of stern lift Which raises the boat higher out of the water on plane for a
smaller wetted surface. Less drag means less throttle.

The BII is just the lower drive...all lower drives, BI, BII, BIII, are interchangeable.

I have a 1978 24' searay. Factory weight was about 4500lbs but it never was that light.
Last weigh-in she weighed 7680 lbs.

Stock engine was a 350ci 260 HP that averaged 1.55 MPG. Present engine is a 406 ci with
325+ HP and 450+ ft/lbs of torque at 2500 RPM. That's lots of torque in that pre-plane
speed where it's needed. I never hammer it to get on plane. Don't need to. Last mileage
calculation I got 2 MPG, all using regular (87) octane gas. That's really pretty good
for the heavy, older type of hull. To increase mileage, manufacturers made the newer
hulls thinner and thinner. You could feel the hull vibrate with every wave they hit.

Sounds like you have a 14,000+ lb boat. You didn't say but it sounds like all you have
is a single 454.[:O] I can't believe it's pushing your boat satisfactorily...and tubing, too?

Oh, and you never said, do you have flat top pistons or the full dish pistons?
 
I guessed the weight between 14 and 16k so we are right on par with each other. Yep, single 454 at a rated 340hp. I plane out around 28mph, and run an average of 32 to 35mph. Yep it pulls a tube with no issue at all, and that's with 3 aboard the tube and several on the boat. Really don't even notice the drag. That's what I have been saying, power was not ever really a problem, just a bit too much fuel burn. I did struggle once with a lot of people on board and a couple on the large side sitting on the rear seat, I had an issue getting it to crest over, happened twice, never figured out why as engine rpm was the same, everything was equal to when we left and it crested then. That's why I asked about the hub earlier if I should replace that, wondered if it could be slipping since I never figured out why.

Don't know on the pistons yet, will be winter before I do. Right now, while the weather is still nice, I am going over the engine room, painting it, fixing wiring issues, repairing the water heater, cleaning, all new hoses and bilge pumps (found that the housing was cracked on the main pump today, did not notice that until I went to remount it) putting all the wiring in split tube to make things more neat and organized, etc. Everything I can do while it is still warm and dry out. Found the ground line to the gimbal housing was broke, going to have to fix that................D..........
 
I may have missed it but are you going to examine your fuel tank(s) while the engine is out? If its from 1989 too, it may be getting some pitting and at least should be examined/cleaned and painted. Mine are that old and if/when the engines are out the tanks will follow for probable replacement.

BTW are you going to have the crank machined? I didn't see that one either and if you in fact spun a bearing the crank will need work.
 
Removal of my fuel tank does not appear possible, at least not yet, can not find anywhere to take it out. It is almost like they laid the stringers, bolted the tank to them, and poured the boat around it. Will probably pull the sending unit and bore scope it though. Have to pull that anyway as I need to add a return port.

Not sure on the crank yet, just have to see what damage was done. Will likely have to have it turned, dont see any real way around that short of just replacing it, and that is going to hurt my feelings a bit.........D........
 
So the weather finally turned bad and I started the tear down today. And of course the first mana fold I try to take off broke all 8 bolts off. Grrrr. Finally just said the heck with it and went for a beer.........D......
 
Good plan; at least you have a sound strategy. :-) Gotta replace risers n elbows on twins very soon myself.
 
Going to start back on it today. Manifold would not come off the broken bolts so I will have to partly drill them out so I can at least get it off. The bolts will be stainless upon re-assembly for sure. Had already decided to change most of the external bolts to stainless when I go back together. Might do stainless studs on the exhaust manifolds and use nuts instead of bolts........D.........
 
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