Need help in identifying and safely restoring this Evinrude V8 300hp

[RoyE]

1.670 is a relatively mild exhaust port heigth. Are the transfers set the same height as the rear boost? I would put finger ports in it. The motor should be a good lake build.

Not sure what you mean. The port height of the transfers and the boost port seem to be the same.

Have another question. There is a T-shaped check valve between the lower crankcase bearing and upper cranksbase bearing (part no 0394892).


The extra barb is for a hose that connects to intake manifold check valve of #7. The T-shaped check valve is broken and a new one is quite expensive.

Later model blocks had just an inline check valve between the upper and lower crankcase bearings (part no 0434927). It is also a lot cheaper.


Question is can I just put the inline check valve and do away with the extra connection of the recirculation line from the intake of cylinder #7? Why is it connected in the first place?

Was there any sort of change to the powerhead which made it sufficient to only use the inline check valve on later models?

[rude tim]

The stock V8 has the rear boost lower than the transfers. If the rear boost is at the same height it is better.

[powerabout]

The reason for the tee was to aerate the oil so it would lift it to the top.
I cant remember if there was a bulletin saying its no longer needed so just the one way valve will work.
Id be putting a bit of clear hose on to test it if you change.
Hopefully Racer will chime in

[RoyE]

Thanks for the replies, I managed to find a tee check valve for a reasonable price so that will be going back in.

Progress is slow but steady.

Cleaned all carbs in the ultrasoon cleaner. All new gaskets, needles, seats, floats. Intake manifolds cleaned in the ultrasoon cleaner. Painted the block. Put CCMS reeds in it. Putting it back together with all new gaskets.

[RoyE]

Haven't updated for a while but we've been working on it.

Mounted fuel rail


Remounted the other stuff, ignition, starter motor etc. Also redid the engine harness. Engine will be installed on a hydroplane and owner preferred to have the trim & tilt sytem removed and set it manually.


As all 8 check valves were broken, we used the mercury check valves as they were easier to get and somewhat cheaper (don't mind the red cable on the ground connection)


Tried starting it next day and it seemed to run alright

[RoyE]

Now the powerhead was more or less finished, all could come back together. The owner had the mid and bracket sand blasted.


The lower has all new bearings, seals and prop shaft. Bobs nosecone is welded on, finishing still needs to be done.

Next day it wouldn't run properly. It would at least run when the powerhead was on the pallet but now it would barely stay running.

After diagnosing I found out it was double firing on a couple of cylinders, indicating that the powerpacks were going out. Stator didn't look too good either and the owner decided to go for a all new CDI ignition system (stator, timer base, powerpack, coils, plug wires).


We had a double powerpack ignition system with the corresponding flywheel. However, for that ignition system, no new timer base is available from CDI. After some research on scream & fly I found that the newer ignition system can be used with the older flywheel if you disconnect the orange wires to disable QuickStart (and consequently the rev limiter and SLOW).

All new ignition mounted and good to go, however it wouldn't run. Timing seemed way off, wouldn't even fire once.

I was tired and couldn't find the problem. Next day I suddenly realised that I connected the (if I remember correctly) yellow/red wire to the starter solenoid. It is supposed to power the pack while starting. The newer ignition system always advances timing during starting and running for the first few seconds and does so using the QuickStart system. While the orange wires were disconnected, engine still was in QuickStart mode during starting and therefore timing was way off as the flywheel doesn't support it.

Disconnected yellow/red wire and BOOM she ran

[RoyE]

The owner now needs to finish his boat before the engine can be placed on the transom. I had the privilege to work on this motor as a hobby project, and I learned a lot.

The engine will go on a home-build hydroplane with string steering. The owner had a wing plate made (this was before the new ignition system was installed).


This was the boat, still with a 2.5 260


It is now under construction for some changes. He took the cockpit of an old raceboat. Everything needs to be tied together and repainted.

[powerabout]

do you have the shift interrupt harness plugged in, thats where the inter pak diodes are, same for single or twin pack.
It wont run properly without it.

[BOATMANBLUES]

The timer base magnets are indexed differently on 86/87 flywheels...if you mix timer bases up between the two it will either be way retarded or way advanced...I have rebuilt a few destroyed V6s that came in with mismatched timer bases...look up OMC flywheel trigger map on line and compare what you have on your flywheel to which TB your running...

[engineer73]

Where are you running your upper most fuel line? I assume you are feeding it from the bottom? Is the upper recirculating? Reason I ask is I am building the same setup for my 3.0L looper.

[RoyE]

do you have the shift interrupt harness plugged in, thats where the inter pak diodes are, same for single or twin pack.
It wont run properly without it.

I don't have it plugged in. I don't understand why the motor would not run properly without it? Can you explain?

The timer base magnets are indexed differently on 86/87 flywheels...if you mix timer bases up between the two it will either be way retarded or way advanced...I have rebuilt a few destroyed V6s that came in with mismatched timer bases...look up OMC flywheel trigger map on line and compare what you have on your flywheel to which TB your running...

I understand the difference. The newer style timerbase is on it with the older style flywheel. It works as long as QuickStart is not engaged.

Where are you running your upper most fuel line? I assume you are feeding it from the bottom? Is the upper recirculating? Reason I ask is I am building the same setup for my 3.0L looper.

The upper most fuel line is going to the upper most carb. I did it that way so that any air could escape from the system. I am feeding it from the bottom yes. I have no recirculation. I cannot tell you if and how this works in practice as the boat is not finished yet.

[powerabout]

the pack whether 2 separate or in one box its still 2 packs so to stop the engine it shorts the capacitors to ground.
Follow the wiring from the pack, there are 2 black yellows, they need diodes between them so they dont interact.
the diodes are in the shift harness not the engine loom.
Unless CDI have done something else?
Do you have a manual, it explains it.