Hop-up 1961 Evinrude 40 h.p.

[aqotwf]

I'm trying to make modifications to my 40 h.p. (reeds etc.) to get more power out of it (without turning it into a 5,000 rpm+ hand granade). I've considered high-octane fuel, but fear it will destroy my seals and fuel pump. <br />Because of reed valves, I don't want to try a blower/larger carb. Maybe I can swap the carb and manifold plate to accomodate a larger carb...but I'm uncertain how the reeds will respond to that... At some point exhaust will hold me back too. <br />Anyone have any ideas besides a new engine?<br />Thanks in advance-

 

[lark2004]

Re: Hop-up 1961 Evinrude 40 h.p.

are you for real? The old BigTwin motors are great motors as is. If you really want more Hp, buy a bigger engine. If you want to destroy a really rugged reliable motor, mess with the 40, your call.

 

[Paul Moir]

Re: Hop-up 1961 Evinrude 40 h.p.

If I were going to try to power up a 40hp, the first thing I would do is work on the exhaust. There's a reason all modern 2-stroke outboards use a tuner, and that is if you can improve the scavanging efficiency, you'll gain power. Naturally, tuned pipes are even better but you'll be sacraficing quiet.<br />High octane fuel by itself won't make a bit of difference. Theoretically you could then shave the head to increase compression, but that's not a good way to gain power.<br />If you have a manual shift lower unit, there's a lot to be gained by switching over to something a little more racier. <br /><br />A new engine is the most reasonable way to proceed. Either that or loose weight from your boat and work on setup. There's a lot more available from that.

 

[R.Johnson]

Re: Hop-up 1961 Evinrude 40 h.p.

You may be able to get it to use more gas, but I doubt it. The factory had that pretty well covered.

 

[bfitz]

Re: Hop-up 1961 Evinrude 40 h.p.

can be done, but you'll have to make everything.<br />single carb will kill breathing, as will reed size, unless you adapt different reed...<br />expansion chamber exhaust can provide a huge gain BUT a deflector piston will absorb enough heat to over expand and stick the engine or, and more likely, the piston crown will melt from the scavenging effects....read The Two Stroke Tuner's handbook by Gordon Jennings, or the high performance two book[I forget the title] by A. Graham Bell...that'll give you an idea as to what's involved and how far you're willing to go..<br />there's guy in Maine that does this type of work...might want to talk to him...<br />good luck

 

[CATransplant]

Re: Hop-up 1961 Evinrude 40 h.p.

Interesting project, but unlikely to produce much in the way of results, I'd say. You have a solid old outboard. Lots of us here have the same or similar Big Twins.<br /><br />As R.Johnson said, you can probably get yours to suck up even more fuel than it already does, but I doubt that you'll get much more power out of it without drastic modifications, and those would ruin the solid reliability of these old workhorses.<br /><br />If yours is running great, why not find another outboard to mess around with. That way, you'll still be able to get on the water when that one blows up.

 

[aqotwf]

Re: Hop-up 1961 Evinrude 40 h.p.

Thanks for the replies y'all...<br />The 'ol BigTwin is a solid engine, but you know how one is always searching to get the most out of what they've got. <br />I've looked into the Boyeson co. for high performance reeds, but I'd probably be better off chasing something that says Ficht on it if I really want acceleration on the water. I've got this 40 h.p. on a 14' Crestliner Commodore now (1955) and she goes pretty good.

 

[aqotwf]

Re: Hop-up 1961 Evinrude 40 h.p.

Does anyone know of any high-speed lower units to fit the BigTwin 40? I recall reading about the Cornaire that fit the 1951 BigTwin in Peter Hunn's Old Outboard book, but am uncertain if there was something similar to it for a 1961 model. <br />Maybe I'll get over the modification idea...someday<br />Thanks for your responses in advance.

 

[Paul Moir]

Re: Hop-up 1961 Evinrude 40 h.p.

You might try begging Chinewalker for his one:<br /> Click here.<br /><br />I think it's close to a bolt-on for your 40hp. Mind you, if I find out where you live I'll drive down and steal it from you. <br />(click my "man-next-to-house icon")<br />Another idea would be to find some modern lower unit and try to marry it up. That way you'd get forward and neutral too.<br /><br />Seriously though, there are big gains to be had by working on setup. Raising the engine up and improving the water pump & supply system so you can raise it up further, loosing weight, etc.<br /><br />There are no boysens to fit your 40hp. The only low hp ones for Johnny/Rude engines don't seem to get the same great comments you hear from their higher hp reed sets.

 

[aqotwf]

Re: Hop-up 1961 Evinrude 40 h.p.

Setup would be a good thing to change a bit...my boat could loose a little weight - that goes for me too. <br />I plan on bringing one of my 35 h.p. blocks to have a machinist open up the ports on it. That one can be my test engine. Maybe I'll be able to find some larger reeds and fit a modified carb. as well. Finding a newer lower unit with the same bolt pattern might be a problem, but who knows. <br />Yea I'm eccentric, but isn't it a little like modifying a small block 350? <br /><br />Cheers and thanks for the help all

 

[Chinewalker]

Re: Hop-up 1961 Evinrude 40 h.p.

Hi OE40,<br /> If your machinist is going to tweak the 35 block, then make sure he does a couple of things. First - don't alter the port timing. That means don't alter the top and bottom reach of the ports. Second, make sure there is a little bit of a chamfer on the port edges so you don't catch a ring on the edge. The best way to open up one of those motors is to square off the ports (vertically) and smooth out the passages leading up to them (intake) and out from them (exhaust) to increase flow. Make sure to leave enough of the webbing between the ports so as to retain the strength of the block. <br /> If you're going to tweak a 35, you can install the 40hp intake manifold and reed plate. I'd also find a later 33hp head which will not have the compression release junk in the dome.<br /> Also, with the 35hp, find an early manual start 25hp flywheel (smooth sides, without a ring gear ) as it is a bit lighter and less likely to snap a crankshaft.<br /> Using a later lower unit will gain you nothing - they're actually heavier and have a larger profile. You can mess around with some old Michigan AJ (Aqua Jet) 2-blade bronze wheels. I think the Michigan Wheel site has some listings for props, even though they no longer carry them. It would give you a search for eBay, etc.<br /> Prop, set-up and hull condition will give you as much or more of a performance boost, for far less invested, than anything you can do to the powerhead(s)....<br /><br />- Scott

 

[itstippy]

Re: Hop-up 1961 Evinrude 40 h.p.

What IS it with some people?? A guy at work changed the pulleys on his snowblower and sprays vegetable oil in the chute to reduce friction. He claims he can fling snow all the way across the street and fill up the driveways on the other side. Gotta love you gearheads!<br />MORE POWER, SCOTTIE!

 

[alden135]

Re: Hop-up 1961 Evinrude 40 h.p.

Add more chrome to increase power and performance.