1989 Evinrude VRO 90 HP Questions

I have a 1989 Evinrude VRO 90 HP on a 1989 15' 6" Kingfisher bass boat. I have disabled the VRO, changed plugs, fuel lines and fuel filter. It runs great but I cannot get it faster than 40mph (WOT) at 4800 RPM's with just me in the boat. It currently has a 13 x 19 alum. prop that has some damage on 2 of the fins. I am currently shopping for a new prop but unsure if I should stay with 13 x 19 or drop to a lower pitch. I have also read about rising the motor up a notch or 2 to increase RPM's and top end speed. I am also unsure where the RPM's should be for this motor at WOT. Any and all responses are welcome. Thank you in advance.

Re: 1989 Evinrude VRO 90 HP Questions

I would be shooting for 5500- 5800 rmp on that motor. You will need a good undamaged prop. You can start by raising the motor which will be free or nearly so. Raise it as high as you can without cavitation or ventilation in the turns. Also make sure it is still picking up and pumping water good. See how many rpm's you gain by doing that and then you can make a good educated guess about which prop you may need. You will probably gain about 200 rpm going from a 19 pitch to a 17 pitch, but every prop is different.

Re: 1989 Evinrude VRO 90 HP Questions

1st are you sure the boat does not have any unwanted load/weight. like water saturated foam.

Re: 1989 Evinrude VRO 90 HP Questions

Thanks to those that replied. I was reading the book I have on my motor and it states that the WOT RPM's should be between 4500 and 5500. I am right in the middle of that range. I discovered that I had a crimped fuel line. After correcting it, I took the boat out to do some fishing and was able to get the RPM's up to 5100 which gave me 43 MHP at WOT. I did not raise the motor yet as I want to try out the new prop I bought for it this weekend. I found a 13 x 19 OMC Alum. prop, same size and pitch that is on it now for 76.00 with hub. Great price. I am thinking with the new undamaged prop, I may be able to get 45 MPH out of her. I will be happy with that.

Re: 1989 Evinrude VRO 90 HP Questions

In order for the motor to live a long life you need to get the top capable rpms up over 5500. With todays fuel 5800 is a good target.

Re: 1989 Evinrude VRO 90 HP Questions

I failed to mention that I think there may be something wrong with my trim. At WOT, I cannot get the boat to *bounce* like it used to. I remember the boat going much faster then it does now. I have checked the fluid and it seems full. Is there a safety on the trim when the motor is in gear? I plan to put the new prop on and test it this weekend. One one of the fins on the old prop is curved over like an inch or so. I will raise the motor if needed. I really appreciate all the infomation ya'll have provided me. thank you in advance

Re: 1989 Evinrude VRO 90 HP Questions

"old prop is curved over like an inch or so. " no wonder, hope you did not damage the lower unit bearings.

Re: 1989 Evinrude VRO 90 HP Questions

That is how the prop was when I got it from my mother in law. It was my father in laws boat and the past few years his grandsons used it and Lord knows what they did. I have drained the and filled the lower unit and there was no water in the oil and the shaft is good and solid.
I have replaced the prop tonight with a OMC 13 x19 (didn't realize how bad the old prop was until I compared the new one with the old). I also raised the motor 1 notch. I am thinking I may run around 45 or better now. I will let you all know how it runs this weekend as I plan to take it out Saturday morning.

Re: 1989 Evinrude VRO 90 HP Questions

hows the compression?

Re: 1989 Evinrude VRO 90 HP Questions

I do not know how the compression is as I have not had it tested.

Re: 1989 Evinrude VRO 90 HP Questions

OK... put the boat in this morning with the new prop and the motor raised 1 notch. At WOT, I am running 45 MPG (per GPS) @ 5100 RMP's. RPM's about the same but the boat handled better with the new prop. I have a new problem or at least I think it is a problem. Today when I put the boat on the trailer, I had the motor trimmed up like I always do when I load and when I hit the throttle to drive up on the trailer, the motor fell all the way down. It's like the torgue from the engine pushed it down. I am guessing the trim fluid is low or needs to be replaced. If this is the case, I am thinking at WOT I can't trim it up all the way to get maximum RPM's and speed. It makes sense to me but wanted to run it by you all. Any and all responses are welcome. Thank you in advance