A question for Dhadley or anyone may know

[Chief101]

Concerning a 1990 120hp with jet pump. I need to pick up a couple of hundred rpms. I can't seem to do it by changing impellers, so, I was wondering if I could pick some r's by switching the intake manifold and reed blocks to the 140 parts? The engine runs well and I hate to mess about with it but with setup I have I can only get 5200rpm and would like more. Thanks for whatever info I recieve. T

 

[Dhadley]

Re: A question for Dhadley or anyone may know

You can switch the manifolds but either should flow more than 5200 easily. So should the reeds. Did it ever turn more? Have you tried a smaller impeller?

 

[MCM]

Re: A question for Dhadley or anyone may know

Just a few questions T,<br /><br />What size/type boat is this on? Did you just install the drive on the motor or was it a package? How long have you had it? Have you tied raisng the motor with a jack plate yet?<br /><br />I'm assuming you got this for running the Snake or Salmon, up to 30% loss of hp. is common when switching to jets so its important that the motor is big enough for the boat.<br /><br />Since you've already tried different impellers you may have already seen these two web sites, but in case you haven't I'll add them anyway, web page, web page, I don't know if you can use the reed blocks and manifold from the 140, someone else might, ther may be some alternatives listed in those sites that you might try first.<br /><br />Good Luck

 

[Chief101]

Re: A question for Dhadley or anyone may know

Dhadley, I've tried many different impellers and I have settled on the one that gives me the best holeshot which is needed for getting up on plane quickly in whitewater. With the smaller impellers there's a lot of ventilation, direct drive you know. At sea level I can get the r's to 54-5500. The motor doesn't seem to lug any.<br />Mike, yea I'm in the Snake and Salmon a lot, but not limited to those rivers. No jackplate, but I do have the motor as high as I can get it to run comfortable. I put the jet pump on, tho I could have used a 150hp motor, fuel range is important so I settled for the v4. I can get over 40 mph at sea level with this 17' Hewescraft. <br />I've been thru the parts lists for both the 120 and 140hp models and can find only differences in the intake and exhaust parts. Been a while so I don't remember more than reeds and intake parts. Thanks Terry

 

[Chief101]

Re: A question for Dhadley or anyone may know

Dhadley, I did try the smaller impeller but all it did was spin at 6000 and make a lot of bubbles. I'm not at all unsatisfied with the way the motor runs, just think that more rpm's will help the engine last longer. Terry

 

[Dhadley]

Re: A question for Dhadley or anyone may know

OK, so the motor will go up in r's. Thats good. Jets are a bit different than a prop. They dont seem to create the combustion heat that a prop does. Maybe it has something to do with being less efficient. <br /><br />If you can get to 5500 at sea level I'd say youre OK. Have you played with the jetting at altitude?

 

[Chief101]

Re: A question for Dhadley or anyone may know

You are right about jets acting different than props. When I go from idle to wot in one motion the r's go right up to wot without any hesitation, it takes time for the boat to catch up. The stern digs a hole, then, when it gets a bite it shoots out onto plane. I havn't messed with the jetting but I would be willing to if you think it's something that would help. Remember tho, I get to sea level periodically. I really think that impeller technology could take care of the situation, but, it isn't there yet. Terry