How can I modify my 300 Evinrude

[Daveski]

I just finished doing a compression test on my newly purchased 1990 22sst Stoker with a carb. 300hp Evinrude. Even 120psi across the board. After I corrected the two swapped plug wires, that the previous owner left me, I think it will run better. Now that I know the lower end is pumping equally, how do I make it 'Scream and Fly'? It appears stock. Also What kind of prop should I run? Is it summer yet?

[BenKeith]

One of the main guru's on that motor is recovering from back surgery. I'f you really want to make it S&F, wait until Jan/Feb, take it down to Stanton CA. and let Stoker do his magic on it. I've also herd Bill Gohr knows a thing or two about them, might want to talk to him. Most of us can do a pretty good job at screwing up the V6's, we ought to really be able to play hell with a V-8, giving you all kinds of advise, and knowing nothing about it.

[Daveski]

not what I wanted to hear, but I like the Honesty

[speedracer]

I have a 90 also, Ill pass on what I did to mine so you have somthing to go on. First pull the heads and plug the exhaust relief bleed holes with two part epoxy, then install the heads with new head gaskets. Next remove the air box and disguard it, next, that year motor had the worst intake maninfold omc ever produced it has to go, you need a maninfold off of a 1986,87,88 or 89 V-6 it will require two upper V-6 maninfolds. Once you locate these install a set of boysen reeds, now you need to flow the maninfold entry path to the reed block easily done with a die grinder. Next, that motor came with 71-D main jets being you removed the air box you will need to go to 73-D. Install a new set of L 77JC4, set timing at 18 BTDC at 5,000 under load that's about all you can do to this motor without going inside, lots of money/trouble. Mine spins a 28 clever at 6700 at about 90mph on a 21 Talon, Very heavy boat. Hope this helps.

[Daveski]

What does pluging the exhaust bleed holes do and are they in the heads or in the cylinder walls, or the block deck? Is that v-6 intake manifold a two piece manifold? Call me an idiot, but my math says a v-6 manifold plus a v-6 manifold equals v-4 too much. Just kidding, I know all about car engines, just learning about this thing, and it don't look like my CR250, which I know enough to hurt myself. What about those 2 plug heads? :confused:

[BenKeith]

Daveski.

I can help you a little on those questions. The V-6 runs one V-4 mainfold and on two port manifold. What you need are two of the V-4 portions of the manifolds.

The exhaust reliefs are small holes drilled in the cylinder wall just above the exhaust port. Plugging them will increase compression. Clean them good with pipe cleaners and brake part cleaner or carb cleaner and then fill them in with marine-tex. Stick you finger in the exhaust port, make sure it come through and smooth it off.

The only two plug heads I've seen are the ones made by Land and Sea. Theirs are solid billet heads and you'll run into all kinds of heat problems with theirs.


Not sure what heads the 90 motor came with, but if it has those big open chamber heads, might want to see if some small chamber heads are available for it. They are a much better head.

[Daveski]

Ah, I get it, that makes sense, I can see it in my mind now. Well enough for now, I must go riding in the sand dunes for the weekend. If anyone thinks of more tips I will get back to ya next week. I can't wait to start experimenting with the evinrude!

[Daveski]

Does anyone else have any overheating problems with billet heads?

[inspectorlance]

Al Stoker is the man you need to talk to. He is the one who originaly built the boat and most likley the man that built the motor that you have. We all hope he is doing well. Everyone here is giving you great info. Talking to AL is worth it's weight in gold and worth the wait if you want it done right. We all want to Scream And Fly ! No one knows your boat better that Al and few come close to his knowledge of OMC outboard motors.

[Daveski]

Does Al Stoker chat on this site or is that considered work talk? My buddies are telling me to put a Merc on my Stoker, but I want the original feel. I also don't want Al to kick my butt for changing this beauty! I just want to enhance her!

[inspectorlance]

Yes Al Stoker post on here almost daily, unit his back surgery. His user name is ( Racer ) . I hope to see him on here soon. I had a Johnson / Evenrude 225 built by him just about a month ago. As a daily driver that is reliable he got me dyno 279.3 HP. This thing just screams . Look up Racer under the Member section at the top of this page, and read the posts under (Racer).
I am wondering ? Do you know that you have one of the best built HP boats out there ? Your motor may be stock, but most likley it has be played with by Al. I took my boat All the way from Seattle to Stanton for Al to do the work on it. I did my homework and he is the master.
Post a pict of your boat we would love to see it !!!
Lance

[Markus]

Daveski,

Like pretty much all heads that do not have water jackets, the L&S billet heads get way too hot.

However, although I have never heard of Mercury and Yamaha owners that have had good luck with them, I have heard a couple of stories of OMC people who have used them successfully. Supposedly, they can be made to work on an OMC if the engine is jetted so richly that the cooling from the fuel compensates for the lack of water cooling.

Then, on the other hand, since the increased performance pretty much only comes from the increase in compression, you would be better off having a set of stock OMC heads cut.

[speedracer]

After I pluged The exhust relief holes my 8 had 140 lbs of cranking comp , I know that sounds high but I bought the motor from a dealer who swears the heads were never off since new, 140 is perfect for 93 anyway. Heard nothing but bad stuff about land and junk heads.

[Daveski]

Don't get me wrong, I drove 60 hours, round trip, to purchase this boat. I know this is a hot boat, it looks hot and handles like an oversized champ boat. I just want to scare the heck out of my girlfriend. But you know faster is always better! Here she is..........:D

[Daveski]

Here she is!

[inspectorlance]

Thats a good looking boat !! How fast have you had her up to ?

[Daveski]

Well I only took her out once so far, it was a disapointing 50 mph, burned 30 gallons of gas. But when I popped the engine cover to do a compession test I found two plug wires crossed, so I am still waiting to see the true potential. I even had a dream last night that I hit something boating and tore my prop up. Stupid winter weather!

[espen]

Never forget the sight of norvegian offshore 1 driver andreas ugland s cougar 28 cat with 2 Johnson v8s. Both the engine covers where off and I could see the dual spark plug heads....I figured out I could not afford to change the sparkplugs on that boat...32 sparkplugs ....a days work:D
this was in the 80s.
Espen

[markt111]

how would the above mods work on a 1994 Johnson 250 Ocean Pro? was the 1994 a similar setup?