RPM and Speed???? Need Assistance

[Ranger115hp]

I need a little assistance getting my boat buck up to speed. I have a 04 285pxl w/150hp Johnson. When i originally bought the boat it was rigged with a 24 pitch Raker prop. I was only turning over 5000 RPM's at full throttle but I was getting 61 MPH (by myself). That was about 2 years ago. I am now only getting 4900 RPM's at full throttle and getting a Max speed of 56 MPH. I did do a little damage to the prop and I plan on replacing it, but would a damaged prop cause that much speed loss? I was reading in my motor manual and it said that my red line was 5600 RPM's. Should I be pushing that Much RPM's on my setup. I am thinking of going with a 22 pitch Raker to increase my RPM's?

What do you think I should do to get the best preformance out of my Motor

[ep72]

Yes prop damage can hurt MPH that much. As far as RPM wheres motor height set at? Has it ever been decarbed......does the prop barrel have a lot of black carbon build up on it? Have the plugs been changed in the last year or so?

Doesnt sound like it ever turned 5600 even when it was new.......motor could be set too deep. A good 24 raker ought to make that rig haul butt. Not sure I would go down to a 22....a 24 with the correct setup will do fine.

[Ranger115hp]

I do not belive that the motor has ever been decarbed. The Prop Barrel does indeed have alot of black Carbon built up on it. I have changed the plugs no to long ago. I do belive i changed them in the fall.

Since i had the boat it never turned 5600 RPM's. I did play with the jackplate and it is set for the best preformance for hole shots and speed.

I do plan on getting a new prop for my boat. Would a 22 pitch hurt my preformance rather than help me? Just trying to decide which prop would be the best for my setup before purchasing one and what do you think the issue could be? Is 61MPH good for my boat or sould it be faster. I would be fine with 61 mph but right now i am stuck on 55-56 MPH.

JUSTIN

[ep72]

61 isnt bad. Might get a few more MPH out of her with your repaired and worked 24.
Heavy carbon buildup may be hindering some. The gurus in the John/Rude form can give you the low down on decarbing your motor. Its real easy on your 150.

I would think a 22 will be great for hole shot, it will hinder top end though.

Something isnt letting her rev past 5000 and it should with no trouble spinning a 24 Raker. Another thing to look into is to verify the linkage is working properly and giving a true WOT and check that the tach is indeed reading correct.

[Chasman]

get the prop repaired. if you want performance, you should think about getting a 4 blad prop. A renagade or TRO4, 23 pitch or 25 pitch. smoother ride and I get about the same speed between my raker and renegade. just for thought. I keep my raker as a spare.

[thebassoutlaw]

Agree, get the 24 fixed or a new one. A 22 wiil jerk you out of the hole but you'll easily get OVER 5600 on top

[tmbullet]

If I were u I would run mercury quick clean in a recommended amount to the amount of gas u run, that will clean the carbon of the pistons and heads and the prop barrel. The build up of carbon will make more compression and your motor will have detonation and spark knock which u will not here, run the recommened amount all the time it will help your motor stay clean and carbon free, inturn it will perform 100 percent at all times.


Modified by tmbullet at 9:36 AM 12/27/2009

[Buccaneer]

Ranger - I have the same rig, '04 285ProXL and 150 Johnson Carb, 6" jackplate and 24 Raker. The best I have ever gotten is 61.5mph at 5400 RPM, Winter-time and very low humidity. Summer I can get 60.5mph and about 5300 max RPM's. The 24 Raker is the right prop for the boat.
You did not say what your propshaft to pad measurement was. I am at 3 3/8" below the pad and intend to move up to 3.25" once I get my Raker back from Mark after a B&B job. Based on my experience, anything below 3 3/8" is taking away from your performance.
Are you running BRP XD-50 oil? Consider going to XD-100 and eliminate the carbon issue. The minor damage to your prop will effect the performance, get the Raker fixed worked by Mark.

[Ranger115hp]

That is what my local marine shop recomended at the time was mercury quick clean so i have been mixing that with the gas. There are not that many stores to get oil around here. The only oil I can find at a reasonable price is the PenzOil TCW3, so that is what i have been running. I am not sure what my pad measurements are right now, but i do now that my boat jackplate is definetly set in the right position for the motor/shaft. I spent several hours adjusting it to get the best overal preformance out of her. I indeed have to get a new prop, the Raker I have now is beyond repair, the cup on one of the ears is almost gone.

So i guess you guys are saying to stay(have to get one) with the 24 Raker and get a TRUE wot RPM reading from an alternative device to see if my tach is reading correctly?

I guess if i want to get more that 62 MPH i need to step up to the Evolution. LOL

You guys have been very helpful and greatly appreciate all of your advice. Is there anything else that i need to look into? I just want her to run at optimal preformance.

[ep72]

What i said was to verify you ARE getting to WOT by checking that the linkage is adjusted correctly and opening the butterflies all the way at full throttle. And having the tach checked to make sure its functioning properly.

Just normal things to check when the motor isnt turning the rpm it should. Seafoam or quick clean is a good idea too. Could be a number of reasons your not turning more than 5k.

[Buccaneer]

Ranger - Unless you are running an HO 150 Johnson, fuel injected model, 62 and maybe, just maybe 63, is the top end out of the 285PXL/150/24 Raker combo. That's just the way it is without some sort of performance upgrade with the motor. The '04 150 Carb Johnsons can only give so much.

[tmbullet]

Hey ranger 115 if you get a new prop send to mark croxton of marks props he will blue print and balance your raker and you will more than likely get at least 3 or more miles an hour out of your rig, trust this guy is second to none when it comes to props. Also I was recommended to run valvoline tcw 3 by all outboard mechanics, they say it is the best oil on the market for outboards bar none. Good luck and happy new year

[Buccaneer]

Ranger - To TMBullet's point, I am expecting my Raker back from Mark next week and will report in on the improvements. If I could get 2 mph more I will be impressed. What I am hoping for is to eliminate an odd vibration and hope the Blueprint job allows me to move up another 1/4" or so to get a few more RPM. Will advise.

[tmbullet]

I thing you will be pleasantly surprised , I think you will get more than what you think , but it is ok tothink a little low that way you be very pleased . good luck

[Buccaneer]

Well I got my prop back from Mark and she sure do look purty! However, at 20 degrees and snow in the forecast through the weekend I think it may be a little bit before I can run it on Old Hickory. Hell, might hit an ice berg and go down like the Titanic!

[tmbullet]