Johnson v4 90 to 115?

[eriklepe]

I have a 90' Johnson v4 and was wondering if anyone have a clue if it's able to tune it up to 115HP. The two engines are about identical, so it must be able...<br />If anyone got any idea of how this is possible I gladly receive tips..;-)<br />If there is any way to get it run better I'll be satisfyed...I got 45 Knots on it now, and I'll think a 115 would push it up a couple of knots more. I got a Raker prop on it now and the boat is 14.3 feet long.Pictures of the boat & engine.

 

[Firewood]

Re: Johnson v4 90 to 115?

I asked the same question not long ago. Basically I was told it has to do with the exhaust manifold and larger bore carbs. So I'd imagine you could get new carbs or manifold and get some more hp. Supposedly the 115 has a bubbled out exhaust manifold versus the flat one on our 90's. Anyway let me know how it works out, I never did anything with mine. I get 35-40 mph so I'm happy. I had looked into Boysen Performance Reeds, seemed like more work than its worth. If I had the motor apart for some important reason then I'd swith to them.<br />Good Luck<br />Ken

 

[Clay]

Re: Johnson v4 90 to 115?

neat boat erik i'll bet its a blast to drive.I have the same motor on a 16 foot ski boat. it ran 42 mph untill i did what you want to do now. you do have to change the exhaust there is also an exhaust tuner.(i think thats what its called)inside .behind the plate that is bolted in. there should be bosses already tapped for it. I had to retap mine they were full of carbon. when these motors were manufactured the tuner was installed before machining the block. this surface needs to be flat. I had mine remachined. not a big deal. as far as the carbs I was told there were the same just jetted different. if any body knows otherwise i would like to hear from them. I also shaved the heads about .015 had it ported and polished and removed the paint and polished the gearcase. the motor dynoed at 127 hp. with a 22 inch raker it now run 57 mph. it was well worth the effort. good luck and ifff you need any help just ask.

 

[eriklepe]

Re: Johnson v4 90 to 115?

ok, thanks guys..I'll try to increase hp now in the winter time, the boat-season here is now over so I won't be able to try out any changes before next year.<br />But I will need your help cootie!<br />Just one more thing, is it true that if you remove the VRO you will get 7-8HP more?

 

[petryshyn]

Re: Johnson v4 90 to 115?

Cootie, I have a 90 hp evinrude in a million pieces down to the last bolt. I sure would be grateful for more indepth information on the modification that you performed to get this increase. Now would be the time for me to do it. Can you e-mail me at petryshyn@yahoo.com<br />thanx

 

[Dhadley]

Re: Johnson v4 90 to 115?

it's very simple once the motor is apart. The biggest thing is the ports. The ports are smaller on the 90 but on the same centerline. You simply center on the existing port and mill it out to the 140 spec. Any machine shop who resleeves can do this and it shouldn't be very expensive.<br /><br />The exhaust manifolds are different. Flat vs "bubbled". Get the two plates used and bolt them on. Here's the deal -- don't worry about the exhaust "stuffers". They are very expensive and have to be machined. We have found that on a boat like yours we have gained as much as 200 RPM by leaving them out. The center rib on the 140 has been machined out at the bottom to match the inner exhaust manifold. You can do this to your 90 when you do the ports. It helps slightly but not a big deal. If you are looking for 6500 RPM or less I wouldn't worry about it. <br /><br />Reeds -- the stock steel reeds start to flutter somewhere around 6200 - 6300 RPM. If you want more Boyesen reeds are a must. <br /><br />Carbs -- you can use the 90 carbs as is. You will have a better holeshot with the smaller throat. If you are looking for top end get a set of 140 carbs. We use the small throat carbs for acceleration and large for more top RPM.<br /><br />Heads -- depends what kind of fuel you want to run. The best stock heads are from the 1979 140 but very close to the 503 and 504 heads (ending numbers stamped on late model heads). Either head with Champion L77JC4 plugs and fresh 87 octane will work fine.<br /><br />Intake -- a ton of untapped power. After the porting this is the area that will yield the most gain. Especially after 6500.<br /><br />The biggest thing is you have to define ahead of time what you are looking for in the end. Looks like a really fun boat. <br /><br />Good luck!

 

[eriklepe]

Re: Johnson v4 90 to 115?

thanks Dhadley, you seem to know alot!<br /><br />I will get an amiracen to transelate all the difficults words for me, my technical english is not so good...<br /> <br />But if i manage to get some more power out of it, do you think I need a prop with higher pitch? I now run a 13 1/4 raker with 20 pitch, I get about 5300 when tilt is right adjusted.<br />I mostly concentrate about the top end speed, the accelaration is already too good!<br />the boat weights only about 250 kilograms, so the 90hp i have now push it out of the hole easyily...<br />I hope to get it over the magical "50 knots", I only have 5 more knots to go...it already runs with a speed faster than it's allowed to drive on the highway here in Norway though... <br /><br />-and another thing...how can i meassure the engines hp after any modifications?<br /><br />thanks again,<br /><br />Erik Kleppe

 

[Dhadley]

Re: Johnson v4 90 to 115?

If you're only turning 5300 now try raising the motor (increase the X dimension) even if it requires installing a jack plate. You aren't getting the full benifit of the horsepower you have now. The Raker is a very decent prop and will most likely work even better at a higher setting. A rule of thumb is if you can use all the trim range without the prop ventalating (slipping) you can run that paticular prop higher. <br /><br />Don't worry about measuring horsepower -- your increase in torque will result in turning the same prop at a higher RPM. Let's get your RPM's up now so we can compare improvements after the work.<br /><br />Good luck!

 

[eriklepe]

Re: Johnson v4 90 to 115?

I've now taken the boat up to the garage, so the engine is now ready for some tuning.<br /><br />Dhadley; you mentioned that I can get lot's of power out of modyfied intakes, but how should I modyfie them?<br />i believe i can get the engine raised an additional 2.5cm without installing any new jack plate, do you think that would help too?<br /><br />thanks,<br /><br />Erik Kleppe