175 Johnson Slow to pPane

[BGRiv]

Newly purchased 17year old 175 EXEIS Johnson does not seem to have the power to push the 20' HydraSport Dual Console over to plane. Engine starts easily, idles well and runs well at idle speed and at manuever speeds, and when it does finaly get on plane however, when accelerating, the hull really labors to climb over the hump with the throttle at full or near full. Also there is not much working "throw" on throttle controls. All acceleration occurs only in the last 1 to 1-1/2" of throttle.

Broker claims to have compression checked engine and all cylinders are marked with 90-95 as compression. Talked to a newer 20' \Grady White owner runing a 150 yamaha 4 stroke who said he had no trouble pushing his hull at 40+ easily. My gauges are flakey and unreliable but at full throttle, seems I can make near 30 at 3500 rpms. Any ideas? I'm on a wait list to get her into a good OMC mechanic.

 

[mrcj001]

Re: 175 Johnson Slow to pPane

The control cables are probably stretched causing your woes. They are probably 17 years old too. Get new cables and do a linc and sync.

 

[emdsapmgr]

Re: 175 Johnson Slow to pPane

Unless you watched the compression testing, I'd probably recheck to establish a baseline. If it is 90-95 as you were told, you should be ok. The next place to check is the prop. You may have too much prop on the boat, causing poor performance and fuel economy. That engine should run at or above 5500 rpm at full throttle. You are lugging the engine at only 3500.

 

[kenmyfam]

Re: 175 Johnson Slow to pPane

Motor height, loading, trim and prop selection are all factors as well. What prop is currently on your set up ??
This does not mean that there is nothing else wrong just that you could have the same issue after spending money on your motor.
An over propped motor is like starting off in a higher gear in your car.
Just a few thoughts on the matter.

 

[BGRiv]

Re: 175 Johnson Slow to pPane

Had mechanic meet me for sea trial. Checked compression and found all ranged between 100 and 110 except lower port cyl which measured 90. Retook measuments with same results. Service manual states greater than 15 psi difference not good.

Also found rectifier/regulator heating up and smoke eminating from under the flywheel cover. Apparently stator is going out as well. He also noted a missing cam from top of carb and carb throttle valve not opening full at WOT. Manual opening of carbs added 500-800 rpm and speed increased to 42 mph.

Once he replaces R/R and Stator and trouble shoops the tach, we'll do more testing with proper rpms. Heres hoping lower port compression is only a sticking ring and ringfree will de-carbon and keep her running a while.

Thanks for the comments and advise.