300 Johnson block question

[findre]

I have a pair of 300's and the port engine threw the #5 rod. I located an Evinrude 275 V8 but I think it's a 3.6 not a 4.0. Does anyone know if the blocks are interchangeable? 3.6 seems to be in real great shape, great compression. I doubt I will notice any power difference between the two. Thanks for any ideas.

 

[muskrat]

Re: 300 Johnson block question

what the model number..

 

[Dhadley]

Re: 300 Johnson block question

The blocks are totally interchangable. In fact you can bore the 3.6 (3.500" std) to 4 liter (3.685" std.) if you want to.<br /><br />The difference between the 300 and the 275 is port timing. If they're set up like V6's I think you're right -- you wont notice the difference. If they're set up correctly you might.

 

[findre]

Re: 300 Johnson block question

Model Number is OMC but they are Johnson 40BPLARF

 

[findre]

Re: 300 Johnson block question

Originally posted by Dhadley:<br /> The blocks are totally interchangable. In fact you can bore the 3.6 (3.500" std) to 4 liter (3.685" std.) if you want to.<br /><br />The difference between the 300 and the 275 is port timing. If they're set up like V6's I think you're right -- you wont notice the difference. If they're set up correctly you might.

Was there a NOT missing on the last sentence?

 

[Dhadley]

Re: 300 Johnson block question

Nope. If they're set up like V6's you arent using all thats available anyway so you probably wont see any difference.<br /><br />If they are set up like V8's you may notice some slight difference between the two.

 

[findre]

Re: 300 Johnson block question

Originally posted by Dhadley:<br /> Nope. If they're set up like V6's you arent using all thats available anyway so you probably wont see any difference.<br /><br />If they are set up like V8's you may notice some slight difference between the two.

They are setup like v8's but the plan was to take off all my electronics, timer base, regs, carbs, etc and put it on the 3.6. Block swap. I think the 3.6 has been bored as the freeze plug looks brand new and the head gasket. The motor has been sitting for the last 4 years at a repair shop, and they guy that owned it never showed to pick it up after the rebuild. The new shop owner got the motor when he bought the place. All the even cyl are showing 105's to 115's the odd side is showing 95's to 105. Is this common for a motor that has been sitting, and do you think it will equalize once it gets broken in? or should I deck the head on the Odd side to match/increase the compression?

 

[Dhadley]

Re: 300 Johnson block question

What was the max rpm on both motors (before the piston stuck)?

 

[findre]

Re: 300 Johnson block question

Originally posted by Dhadley:<br /> What was the max rpm on both motors (before the piston stuck)?

It was 5200 RPM's but smaller props were put on to get it in the 5800 range. Same top speed, just more RPM's.

 

[findre]

Re: 300 Johnson block question

Originally posted by findre:<br />

Originally posted by Dhadley:<br /> What was the max rpm on both motors (before the piston stuck)?

It was 5200 RPM's but smaller props were put on to get it in the 5800 range. Same top speed, just more RPM's.

One more thing. The motor ran great for over a year. The shift cable broke and was stored at a marina for a few months then it was serviced. That is when the piston problem became appearent. I thought there was some foul play at the marina as the motor ran great, the boat was pulled, and when the repair guys fixed the cable and other stuff, they came up with the piston problem. Motor was happy until that. Who knows.

 

[Dhadley]

Re: 300 Johnson block question

Yep, they're set up like V6's. You probably won't see any difference between the 275 and the 300. At 5200 youre not getting anywhere the capability of a 300. 5800 is much closer but you've got a ways to go. The big problem is that the Sea Drives are hard to move up. Not like an outboard unfortunately.<br /><br />What "other stuff" did they fix? What spark plugs are you using?

 

[findre]

Re: 300 Johnson block question

Originally posted by Dhadley:<br /> Yep, they're set up like V6's. You probably won't see any difference between the 275 and the 300. At 5200 youre not getting anywhere the capability of a 300. 5800 is much closer but you've got a ways to go. The big problem is that the Sea Drives are hard to move up. Not like an outboard unfortunately.<br /><br />What "other stuff" did they fix? What spark plugs are you using?

Both engines have all new electronics, timer bases, coils, wires, Champion plugs, carbs are shiney clean, (2) 2140 Malloy fuel pumps to prime and pump with low pressure warning, VRO is disconnected and capped VERY WELL, fuel lines are fitted with brass T's in place of plastic BS in a better flowing format.<br />What RPM should I be at? At 5800 they sound good, but I cant see turning the blenders up much more. I was always afraid of them going POP.

 

[findre]

Re: 300 Johnson block question

Originally posted by findre:<br />

Originally posted by Dhadley:<br /> Yep, they're set up like V6's. You probably won't see any difference between the 275 and the 300. At 5200 youre not getting anywhere the capability of a 300. 5800 is much closer but you've got a ways to go. The big problem is that the Sea Drives are hard to move up. Not like an outboard unfortunately.<br /><br />What "other stuff" did they fix? What spark plugs are you using?

Both engines have all new electronics, timer bases, coils, wires, Champion plugs, carbs are shiney clean, (2) 2140 Malloy fuel pumps to prime and pump with low pressure warning, VRO is disconnected and capped VERY WELL, fuel lines are fitted with brass T's in place of plastic BS in a better flowing format.<br />What RPM should I be at? At 5800 they sound good, but I cant see turning the blenders up much more. I was always afraid of them going POP.

When the boat is underway, they are very high out of the water. I missed a counter rotating pair of lowers with low water pickups on Ebay. But I can do that anytime, if it helps. I dont think they motors should go up much more as when I trim them at high speed, I get some cavitation in the bumps. The present lowers have Big Planners on the lower units. Only the under side of the Planner gets wet. If you see the picture, the boat has a deep V and the nose of the lowers is just below the bottom of the hull. Having the engines higher wouldnt seem to make much of a difference. These motors are pushing a big boat 33 Hydra, so I attributed the power issue more to the 10,000+ pounds than the height of the motors, but I am sure you know way more about these motors than most. Thanks

 

[Dhadley]

Re: 300 Johnson block question

The 300's have rev limiters at 6700. The 275's were limited at 6200. The most efficient way to gain rpm and increase overall performance is to raise the motors. With Sea Drives thats probably out of the realm of possibilities.<br /><br />At 5800 you arent hurting anything but it could be better. What props are you running?<br /><br />Did they figure out what caused the piston to stick?

 

[findre]

Re: 300 Johnson block question

Originally posted by Dhadley:<br /> The 300's have rev limiters at 6700. The 275's were limited at 6200. The most efficient way to gain rpm and increase overall performance is to raise the motors. With Sea Drives thats probably out of the realm of possibilities.<br /><br />At 5800 you arent hurting anything but it could be better. What props are you running?<br /><br />Did they figure out what caused the piston to stick?

WOW 6700, wholly cr@p. Ill check new prop pitch and size and I am pulling head tomorrow and will post results.

 

[findre]

Re: 300 Johnson block question

Originally posted by findre:<br />

Originally posted by Dhadley:<br /> The 300's have rev limiters at 6700. The 275's were limited at 6200. The most efficient way to gain rpm and increase overall performance is to raise the motors. With Sea Drives thats probably out of the realm of possibilities.<br /><br />At 5800 you arent hurting anything but it could be better. What props are you running?<br /><br />Did they figure out what caused the piston to stick?

WOW 6700, wholly cr@p. Ill check new prop pitch and size and I am pulling head tomorrow and will post results.

Props are 15x15 stainless. Trying to pull the head in the AM.

 

[findre]

Re: 300 Johnson block question

I finally got the head pulled and the Number 6 piston was mauled. Totally stuck in the compression stroke, rod was ripped from the wrist pin and metal all over. Cylinder walls look good despite the wreckage and so does the rod and bearings. I was able to pull the carbs, reeds and disconnect the rod and pull (well hammer) the piston through. I am tempted to hone the cylinder and re-piston, bearing and ring without pulling the whole powerhead. SO for now its a V7.