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

[RoyE]

We recently acquired an Evinrude V8 engine. The history is relatively unknown to us; we only know that it was behind a consumer ski race boat. We are now restoring this engine to be in good condition again as it could use some maintenance. We will also add solid mounts etc.

First some pics


The model number on the bracket is E300PLCUR, a 1987 3.6xp motor. However, the model number on the welch plug of the powerhead is E300PLCCA. It also has the ‘tab’ on the head gaskets and the dome on the pistons. So this must be a 4.0 liter V8.

After removing the heads I looked at the porting and it looks like they have been worked. Here are some pics and maybe some of you can say something about it; e.g. whether it is radical or only some matching of the sleeves with the block. I do not have enough experience to say something about it. If measurements are needed I can do them. Pics:

Cylinder 1


Cylinder 2


Cylinder 3


I also noticed that the 2-powerpack ignition system is on this powerhead. I thought that all 4.0 liters were equipped with the single powerpack ignition system. The BRP parts catalog also shows this. Is there a specific reason why this setup would be preferred over the single powerpack system? (or maybe it was just what the previous owner had available at the time)


We saw that there were holes cut in the cowling and that no airbox is present. I would like to know whether it has been rejetted or not. In below pics the model number of the carbs can be seen (398743) and the numbers on the two jets on the front of the carb (upper: 35 and lower: 40). The carb part number does not match the one in the BRP parts catalog but maybe someone will chime in and tell me what I have. I have not measured the venturi diameter yet, but can do that if needed. I also haven't looked at the high speed jet yet.


So main questions for now are
- Any problems with the 4.0 liter powerhead on the 3.6 midsection that might not have been take care of by previous owner? (regarding adapter plate, tuner etc.)
- Anything that can be said about the porting in the pics?
- Carburators don’t match the parts catalog. What kind of carbs are these? What about the jets?

I will update this thread with the progress

[frank jackson]

First off I am not a v8 guy , the heads have been shaved , the flat on the back of the head tells you that . The ignition is the better system it will fire at very low cranking rpm the single will not .The pacs are 8500 rpm limited . The motor may have been bored to the larger bore or a replacement block has been used . I do not remember v8 motors coming with idle reliefs [ holes above exhaust ports ] ...The ports as you said have been worked , if they bored the original 3.6 to 4.0 the ports would need to be corrected to correct port timing . Hope this helps

[RoyE]

Thank you that already helps a lot. I will take compression readings as soon as it is back together, I'm curious. I think the block is a replacement because of the '88 model number in the welch plug.

I'm not sure if the idle reliefs are open, I could not see where air should go through them, but I may need to take a closer look.

[racer]

86/7 ignition. 88 or newer 4.0 block, the 3.6 did not have idle relief.

[gfinch]

Congrats on your Parker race Alan.

[powerabout]

Nice
the main jet is what you need to look at and check all 8

[rude tim]

Post the measurement from the top of the deck to the top of the exhaust port.

[RoyE]

Nice
the main jet is what you need to look at and check all 8

I will remove the main jets and look at the numbers and post them here, thanks.

Post the measurement from the top of the deck to the top of the exhaust port.

I will measure that the next time I work on the motor.

Also found out that the 398743 carbs are apparently mid-bore carbs.

[rude tim]

It has no finger ports so I would imagine it is a mild port job.

[RoyE]

Yesterday I measured the carbs (398743) and they measured approx. 1.45" at the venturi, so they are indeed midbore carbs.

I checked the main jets in all carburetors and they are ALL 56D.

So for every carb on this motor:
Idle jet #40
Intermediate #35
High speed #56D

Would anyone be able to tell me what is stock on this motor? Since the parts catalog doesn't help me further with that.

I also checked the recirculation system, all 8 check valves are not 'one-way' anymore so they don't function anymore.. I think I'll need new ones, my previous 130hp looper ran really bad in the lower rpms when all check valves didn't work properly. Also the check valve to feed the upper crankshaft bearing is shot.

@rude tim; I'll measure the port height when my decent caliper finally will be delivered.

[PanRonnie]

depending on your budget you could contact nico van ackelijen
they are a mercury dealer but also rebuild omc engines
they could add finger ports to the block again depending on the budget
winter is the best time in summer he is often away on the h2o f1 circuit
http://www.merc-racing.com/home/

[racer]

High speed jets must be drill as it would be way to lean with those.

[RoyE]

depending on your budget you could contact nico van ackelijen
they are a mercury dealer but also rebuild omc engines
they could add finger ports to the block again depending on the budget
winter is the best time in summer he is often away on the h2o f1 circuit
http://www.merc-racing.com/home/

Thanks for the advice. It is currently not in the budget to do such a operation. Acutally this motor was bought recently at Nico van Ackelijen and it was on a yellow v-bottom boat, unknown brand.

High speed jets must be drill as it would be way to lean with those.

Thanks for your response. I went back and tried to measure them. They are between 0.089" - 0.090" inner diameter. So they have been drilled like you already thought

Also made a mockup for the fuel manifold



Removed the intake manifold and all looked good. Reeds are in good condition. Found these scratches on every intake around the passage that collects the puddled fuel. Not sure wat happened there and whether it is factory or not.



Also wanted to check the thermostats and found out that none were installed. The gasket or the rubber thing was torn apart in one and still intact in the other. Not sure why anyone would want to remove the thermostats on a motor like this unless they would always go WOT? This engine will mostly be run hard, but I still want to install the thermostats so it will at least get up to temp before we step on it. Do you agree?

[RoyE]

Post the measurement from the top of the deck to the top of the exhaust port.

OK so I tried to measure the distance from top of the deck to top of the exhaust ports.

They are around 1.670" to the exhaust port

And around 2.320" to the boost port.

[rude tim]

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.