'98 70hp Johnson

[JMT]

New to the forum just found it.Have 98 Lowe sea nymph with 70 hp johnson.Runs great,starts easy,and idles good,but is very sluggish coming out of the hole.Takes a long time to plane out.Have changed plugs and fuel filter.Anyone have any ideas what to check next? Thanks

 

[HighTrim]

Re: '98 70hp Johnson

What type of setup do you have, prop pitch, motor height on transom, etc...

 

[JMT]

Re: '98 70hp Johnson

HighTrim, thanks for the quick reply.I think it's a 17 pitch prop.I bought boat new.Seems that just this year it's been really sluggish coming up on plane.Just got home from fishing trip in Ontario where i had exta passenger or two at times. Was embarrasing having to move everyone to front of boat.Once u get planed out ,it runs great.

 

[jtexas]

Re: '98 70hp Johnson

but it does eventually plane out?

Has it been this way since you got it or is it a recent development? Made any recent changes to the hull or load?

Take the airbox cover off and make sure all three carb butterflies are fully horizontal (and not beyond) at WOT.

What size boat? (length, beam, draft)
What's the boat's max HP rating?
What's your RPMs when she reaches her max speed?
What all are you carrying on board? (fuel capacity, livewells, beer, extra large mother-in-law, etc.) Tried moving some weight forward?
Does it ever porpoise?

 

[JMT]

Re: '98 70hp Johnson

JTexas,i have just noticed it this summer.We skied with boat last summer.It was a little slow planining out but it did work.It is 16.5'.Boat is rated for 115hp.I understand that extra weight is gonna slow things down.Just seems to have no power coming out of hole.We have had boat since new,Kids were small.Now they'r mostly grown. I'm heavier.Maybe i've just outgrown it.

 

[jtexas]

Re: '98 70hp Johnson

61% of your max HP rating - borderline underpowered - could just be "personal weight gain" - or, could be performance is degrading a bit. Still, that motor is just getting broke in good........

Have a tachometer?
Done a compression test lately?
Fuel line holding pressure?
You're not using NGK plugs, are you?
Has your area recently introduced ethanol-blended fuel?
Sometimes a carb rebuild just seems to make 'em happier, for no readily apparent reason. Or that could just be my perception. Or a new primer bulb, something to show her you still care.........

Floatation foam gets waterlogged - adds weight. On a boat that new, you'd have had to left it out in the rain a bunch for that (I think).

power trim?