Johnson 110 WOT RPM???

[CaptainPuget]

I just purchased a rebuilt 1987 Johnson 110 hp and installed it on the 18' Aluminum Cuddy and I'm trying to find the right propeller for it. My first try was a 13 ¾ x 15 which is pitched way to low. I was around 5000rpm at a little over half throttle (I didn't want to push the RPMs any higher than that). My next attempt will be a 13 ¼ x 19. Does anyone know what the recommended WOT rpm is for this model?

 

[Jack Shellac]

Re: Johnson 110 WOT RPM???

OMC recommended full throttle RPM is 4500-5500RPM. Ideally you should be in the upper quarter of that range. Just as a reference, I have a 90Hp '91 Johnson. With a 13-1/4 X 17p, it turns 5000RPM. With a 13-1/4 x 15p, it turns 5600RPM. Both are stainless steel. Hope this is of some use.

 

[Jack Shellac]

Re: Johnson 110 WOT RPM???

Just noted your boat is aluminum and probably a lot lighter than my 17-1/2 fiberglass deep-V. I imagine you will get considerably higher speeds and RPM with same props.

 

[bonitoman]

Re: Johnson 110 WOT RPM???

I have an 18 foot flats boat with a 1986 110 johnson that I rebuilt two years ago.I run 13 1/4 x 17. rpms at wot is 5800. You might have to experiment with a couple of aluminum props and then if your satisifed buy the same sized in stainless steel. I would try to get rpms up in the 5500 range. I have seen to many people with rpms 4500 -5000 and they blow the engine by lugging it. I run mine at wot constantly 5800 and use a can of engine tuner every 25 hours. I have put 400 hours on the engine in two years and there is no loss of power. Two strokes are designed to be run at wot. People who do not run them hard and in the upper rpm range tend to have problems.

 

[CaptainPuget]

Re: Johnson 110 WOT RPM???

Thanks for info both of you.<br /><br />Well I tried a 10 mile test run with the 13 ¼ x 19 and I got a top speed of 30.6mph @ 5100 rpm and it burned 6 gallons of gas. Pretty disappointing considering that the 70hp Evinrude that I replaced would push this boat at 30mph give 4 mpg in doing so. It would also plane the boat faster and keep it on plane down to 17mph. The 110hp takes forever to get up and falls off as soon as I back off the throttle. Where's that extra 40 hp going? <br /><br />I think that I have something wrong here besides just finding the right prop.

 

[ob]

Re: Johnson 110 WOT RPM???

Captain , are you using OMC prop ?If so and WOT is 5100 I would switch yet again to a 17" pitch . The added rpms will recover some top end speed.Oh,by the way,I do love my 95 70hp looper.Remember the 70 turns 6000 at WOT.

 

[CaptainPuget]

Re: Johnson 110 WOT RPM???

Actually the 19 is a Turningpoint - Hustler Aluminum Propeller. But I have a slightly beat up OMC 13 ¼ x 17 that I'll try next.<br /><br />I'm kicking myself for trading my 70 in for this 110. It was old (1979) and rusting away but it would turn a 13 x 19 SS at 6000rpm all day every day and never missed a beat. Best motor I ever owned.

 

[Jack Shellac]

Re: Johnson 110 WOT RPM???

The V-4 is giving you a lot more wieght on the stern. I don't know how aluminun boats react to being stern heavy, but imagine more so than heavier boats. Try moving some weight forward and see what happens. This is just a guess, since I've never owned an aluminum boat

 

[93evinrude]

Re: Johnson 110 WOT RPM???

Just in case.<br />Were the two engines mounted so that the cavitation plates were at approx the same level?<br />Are the shafts the same length?<br /><br />From what you have said so far the 17 should be what's needed....hole shot will improve and your top end may as well.

 

[MGuckin]

Re: Johnson 110 WOT RPM???

17" will work but a 19" should work.<br />Sounds like motor may be mounted too low. About 75 lbs. heavier than original causing boat to squat lower which will cause more drag and lugging of motor. <br />You could always vent the prop for a better holeshot. Need to spin it up around 5800-6000 rpm.<br />As far as planing problem is concerned, try a doel fin.

 

[ob]

Re: Johnson 110 WOT RPM???

captain , MG makes excellent point which I overlooked in assuming.Cavitation plate on motor needs to be flush or near flush with mean bottom of boat.Even 1" too deep can have a significant effect on WOT.Case in point, I recently raised my 95 70 hp up 1 hole to highest transom setting and motor runs an amazing 400 rpms higher than before with no cavitation.

 

[MGuckin]

Re: Johnson 110 WOT RPM???

Check out this thread.

 

[DJ]

Re: Johnson 110 WOT RPM???

CaptainPuget,<br /><br />Something doesn't compute. Either the 110 is set way too low, or it's sick.<br /><br />Having owned both a 70 (looper) and a 90 (crossflow basically the same as the 110), there is a WORLD of difference in the two.<br /><br />The 110 has many more cubic inches and the torques between the two isn't even comparable.