Twin 2002 150 Johnson decreasing performance

[roy w. shakun]

26 foot twin counter rotating 150 johnsons cat, that purrs at an idle, broken in by the book, and seemingly have no lulls or deadspots. Top speed has slowed down 10 mph in the last 5 hours of run time. ( on gps ) Can't get the boat to tach more than 4500 on each motor. Used to get 39 mph @ 4000 rpm, now gets 35.8 mph @ 4000 rpm. It feels as if we are lugging a ton of ,,,,, behind the boat. Any ideas would be greatly appreciated.

 

[clanton]

Re: Twin 2002 150 Johnson decreasing performance

If the engines are running smooth do not sound like they are misfiring, and the tach needle is steady, then I would do a compression test. If these are the same engines that has metal shavings in 1 or 2 of the carbs, I would check all of the carbs for trash. You could put a test wheel on and see if the engine will pull the rated rpms for 30 minutes.

 

[seahorse5]

Re: Twin 2002 150 Johnson decreasing performance

Think about it, if you are running the same rpm, 4000, but the boat is now going slower, it's a boat problem. It could be something like trim tabs down or more weight from fuel and/ or water. Twin 150's on a 26' boat may be a bit underpowered. What boat and which props are on it?

 

[G DANE]

Re: Twin 2002 150 Johnson decreasing performance

Have you checked the propellers ?<br /><br />Perhaps you hit something or spun the hub on the one. But if hub issue you should have higher rpm on that motor. Check your propellers or bottum of boat. How long has the boat been in water, is the bottum antifowl painted ?

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

yes same motor with the metal frags, only one though.<br /><br />bottom paint has been the same<br /><br />the boat is only 2500 pounds w/out motors<br /><br />spinning 14 3/4 by 19 vipers, as done by a test by power boat reports on evinrude 150 in 2000, top end 50 plus @ 5000 rpm

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

oh yeah, bilges dry, same amount of fuel, there are no trim tabs<br /><br />the boat hasn't changed to my knowledge, the bottom is clean.<br /><br />it's almost as if the motors a fighting one another even though it tracks nicely.

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

Clanton, (sorry for the extra posts ) , what is a test wheel?

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

Can Macguard prop locks cause any problems, we did install those?????????????????????????????

 

[clanton]

Re: Twin 2002 150 Johnson decreasing performance

If the numbers are correct on your first post, then Seahorse and D DANE are on the right track.<br />A test wheel is just a test prop to run engine in test tank, if it will pull the rated rpms for that engine with the correct test prop, then engine should be sound. The dynos that I have been around only were used with muffs, and if run full throttle over about 5 minutes engines gets hot, and sometimes it takes more then 5 minutes to find problem, you should here a 150 on muffs af full throttle, noisy. I think the trash in the carbuators come from poor QC and cleaning at the factory, and if they were still under warranty, I would want all of the carbs cleaned. If you can find DUNK on the other boards, he may have specs for that boat and be able to tell you what prop and how fast the boat should go.

 

[Beernutz]

Re: Twin 2002 150 Johnson decreasing performance

Doesn't sound like engines. Let me give you one more suggestion. I've seen certain brands of boats that develop a "hook" in the bottom of the hull, ahead of the transom, due to a weakness in construction or design engineering that allows the bottom to collapse somewhat. Sometimes you can see it if you sight down the bottom from the rear of the boat, but a straight-edge would be more accurate. Other times, the bottom looks fine, but the hook develops as water pressure on the bottom increases with speed. It usually is not present when the boat is new, but shows up after a period of pounding and stress on the structure. The result of this phenomenon is akin to fully extended trim tabs. The bow drops and the hull starts plowing, scrubbing off speed, without dropping engine RPM proportionately. It would feel just like you were lugging a ton of .... behind the boat. <br /><br />If you find this condition, it should be covered by warantee.<br /><br />Good luck, Roy!

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

twin vee 26 cc cat spinning 14 3/4 ss viper props, summary of performance <br /><br />please try this to verify the proper hp props etc.<br /><br />what about engine alighnment?<br /><br />they look straight to the eye<br /><br />we are working on the test props<br /><br />there has been no hull distortion, anything is possible, but,,,,,, there is not

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

thanks, and one last question<br /><br />would the motors hold a perfect idle at 650 rpm, with carb problems, both?

 

[G DANE]

Re: Twin 2002 150 Johnson decreasing performance

Roy - i know this is a long shot - have you tried with another GPS ??<br /><br />If you look at the scheme you will see:<br /><br />38.1 mph @ 4000 Rpm - i dont think you can cavitate as much as it needs to go 35 Mph @ 4000 without any damage to propellers. Can it possibly be the GPS changing ?

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

G Dane, 2 waas gps on board. no gps error. i agree, could not cavitate that much,,,,but could the drag be coming from the motors fighting each other, like in terms of out of alignment. your point is well taken though.<br /><br />reality is that they are not cavitating, it's as if they are pushing a bigger load or have more drag. alignment????? how critical ???? these motors are 6 feet apart!

 

[Beernutz]

Re: Twin 2002 150 Johnson decreasing performance

You didn't launch the boat with the trailer still attached to it, did you?

 

[Forktail]

Re: Twin 2002 150 Johnson decreasing performance

Currents, tide, wind, chop, etc all factor in with the GPS. It doesn't take much on water to throw a GPS off 3.1 mph. Heck our tide here runs 10-15 mph (30 foot tides) and the motors always run the same rpm. Against the tide it feels like you're dragging an anchor and the GPS says you're going slower. With the tide its just the opposite. Same rpm.<br /><br />Your motors seem fine.

 

[roy w. shakun]

Re: Twin 2002 150 Johnson decreasing performance

put the trailer in the back yard, this time<br /><br />WOT is getting the same top end as boating mags new long term report of the same boat, with a cabin. about 41 mph. this came today.<br /><br />but the 26 foot cabin model is using suzuki 115's and spinning 14 by 22 ss props getting 41 mph @ 5600 rpm.<br /><br />our cc is about 350 pounds lighter, and was doing 47 mph @ 4600 rpm thru a 2 to 3 foot chop, during the breakin. AND THERE WAS STILL MORE THROTTLE, A LOT!<br /><br />something simple has changed, like<br /><br />alignment??????????????????????????<br /><br />please help we are frustrated, it's not right, and it's new too.<br /><br />please click on the performance # s of this exact boat with same power in previous reply's, thanx

 

[clanton]

Re: Twin 2002 150 Johnson decreasing performance

Try www. thehulltruth,com and ask for DUNK, he can tell you how to align the engines.

 

[grandx]

Re: Twin 2002 150 Johnson decreasing performance

One good thing about duel engines is that one helps you trouble shoot the other. "They used to run at 4500 rpm, now both only at 4000." What could have happened to both engines at the same time? What has changed? What do they share,,, fuel, and the boat they are pushing is the only thing that comes to mind, or what has been done to both? I'm leaning to something changed with the boat (total load, or shifting of load, amount of fuel, water soaked floatation). The prop locks installed may have some affect, I'm not familiar with them, but you could remove them and run to see. Just my 2 cents, I am interested to know what you find in the end. <br /><br /> Best of luck

 

[G DANE]

Re: Twin 2002 150 Johnson decreasing performance

Roy - another thought just crossed my mind:<br /><br />How do you controll throttle on these two wonderfull engines. Hydraulic ? or cables. If something happened to your control like a mechanical failure og air in hydraulic oil, maybe you cant open throttle all the way !!!<br /><br />Then you probably ask: how about the 35 ctr 38 miles. Id take forktails explanation for good on that. You cant cavitate that much, explanation must be in the water. Remove engine covers in harbor, and take a clouse look at carbs. Does the throttle move exact with your controller ?