98 evinrude 90hp crossflow

[Keylargo166]

I have a 98 model evinrude 90hp on a 98 key largo 166. The boat and motor have less than 50hrs on them since new. I've added a tac on the boat because it didn't have one. At wot trimming the motor up I'm right at 4000rpms at 28mph. I was told by a older evinrude/Johnson certified tec. That I could put 140 carbs on it to get more hp. I know the bore on the crossflows are the same new and old. So I put a set of 140 carbs on it but no difference to me at all. But I'm thinking the timing is off some. The motor is like new and never been touched until I replaced the carbs. It runs good just don't come out of the hole good and its lacking rpms. The prop is the factory installed 19p alum. What yall think?

 

[tphoyt]

Should try a different prop.
rpms should be able to reach 5000 to 5500 when needed.

 

[Keylargo166]

That's what I was thinking. 4000rpms is the most I can get out of it. And if I trim it up I can feel a slight vibration and I dont remember it doing that before a changed to the 140 carbs.

 

[racerone]

The intake ports on the 90 HP blocks are smaller than the 115 / 140 HP bubble back blocks.-----Not sure why the certified tech did not explain that to you ???-----So post your compression numbers first.-----Sounds like the motor is running on 3 of 4 cylinders to me.-----Trouble shooting needs to be done here.

 

[Keylargo166]

The intake ports on the 90 HP blocks are smaller than the 115 / 140 HP bubble back blocks.-----Not sure why the certified tech did not explain that to you ???-----So post your compression numbers first.-----Sounds like the motor is running on 3 of 4 cylinders to me.-----Trouble shooting needs to be done here.

Should I put the original carbs back on or change the intake?

 

[Keylargo166]

Should I put the original carbs back on or change the intake? You mean the intake ports casted into the block? Because I see the intake is the same.

 

[racerone]

??----Intake ports are round holes in the cylinders.-----Can not be swapped out.

 

[Faztbullet]

To make more HP from your motor the block would have to be ported bigger and exhaust hump/deflectors added. Cheaper to sell it and get a 120/140 looper

 

[Keylargo166]

??----Intake ports are round holes in the cylinders.-----Can not be swapped out

To make more HP from your motor the block would have to be ported bigger and exhaust hump/deflectors added. Cheaper to sell it and get a 120/140 looper

Will the 140 carbs hurt me as far as power. Because there not much bigger than the 90 carbs. The 90 is 1 3/16 and the 140 is 1 5/16.

 

[Keylargo166]

Well I have a set of 140 carbs for sale if anyone needs them.

 

[jembar]

It really sounds like you're trying to bite too much water. Try a prop with less pitch or take as much weight out of the boat and see if that makes a difference. If you can take out 80 - 100 lbs you should see a difference in the RPMs. It's the easiest thing to check. The actual motor could be fine.

 

[racerone]

Post compression values.