1988 johnson 175hp, doesn't accelerate over 7 mph

[luv2fish13]

Just got this boat, runs good on the muffs, first time out the boat won't accelerate gets to about 7mph then seems like it's gonna shut off unless you throttle it back, when boat is in neutral in the water it revs up fine and sounds strong. The guy i bought it from claims the carbs were rebuilt last fall, any ideas

 

[oldcatamount]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Do a compression test on all cylinders first. They should be around 10 - 15% of each other. You may have a weak cylinder (or two).

 

[SparkieBoat]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

do a spark test also with a spark gap tester set at 7/16 gap

 

[emdsapmgr]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Any V6 will run on 3 or 4 cylinders on the trailer and sound good. You need all 6 when you put it in the lake. Agree that you need to check for spark and do a compression test.

 

[Big flop]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Do all above suggestions and keep in mind carbs rebuilt
last fall could be varnished up again.

 

[metriccrescentwrench]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Does that engine have a shift assist switch? If it does and it's misadjusted it could accound for what you're seeing - it would only be running on 3 cylinders.

Also check timing and carb/linkage adjustment (link-n-sync).

 

[luv2fish13]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

i checked the schematic, and this motor has a shift switch that runs off the starboard powerpack, is this what you are refering to? and how would i check/adjust it? tx

 

[emdsapmgr]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

That engine has a neutral start switch in the control box. Does not have a shift assist. An 88 175 engine should only have one power pack.

 

[metriccrescentwrench]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

i checked the schematic, and this motor has a shift switch that runs off the starboard powerpack, is this what you are refering to? and how would i check/adjust it? tx

That engine has a neutral start switch in the control box. Does not have a shift assist. An 88 175 engine should only have one power pack.

If emdsapmgr says that an '88 175 hp engine doesn't have a shift assist switch then I'd say that either you're engine doesn't have it or you've made a mistake identifying the year.

IF you're positive that it has a shift assist switch (which is mounted in the engine near the shift linkage, and is not the same as the neutral safety switch which resides in the control box) here's what I'd suggest to see if that's what's causing the problem - run the engine on muffs and verify with an inductive timing light that you've got spark on all 6 cylinders in neutral, then shift to forward and see if you've still got spark on all 6. What the shift assist does is to kill one bank of cylinders for a split second as you shift, if it's out of adjustment it could be staying on and killing one bank of cylinders all the time.

 

[luv2fish13]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

after checking the serial #, it turns out to be a 1987, does this have the shift assist switch?

 

[Big flop]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

1987 has twin power packs no shift switch.
Check compression
Check spark
Make sure timer base is advancing
Make sure it is not over propped
All good clean carbs

 

[metriccrescentwrench]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Apparently not. You can see diagrams for any year and size engine at www.shop2.evinrude.com After looking at a handful of engines it appears they only used those on 200's and up.

Now, back to your problem. Do some basic troubleshooting like checking compression; look for differences in spark plug appearance; use an inductive timing light to see if all cylinders are firing when it's idling; use a spark tester to check for quality of spark (should be able to jump a 7/16" gap).

 

[emdsapmgr]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Looks like that shift switch appeared on the 90 degree loopers in 1986.

 

[SparkieBoat]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

did you ever do spark test and compression test??? what were the results? I read post and did not see where you posted results, could have missed it though..

 

[OldPcGuy]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Sorry for jumping in here... I've got similar issues, just not as 'bad' now...

Question - How does one check to "Make sure timer base is advancing"...??

Thanks,

OldPcGuy

 

[luv2fish13]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

been out of town the last couple days, will do the compression, and spark test tommorrow, never did a compression test before, should i use the starter, or crank the motor manually

 

[wilde1j]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Pull all plugs, pull emergency stop lanyard to kill spark, crank engine with starter for a few seconds with tester in place, record each value.

 

[luv2fish13]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

have spark at all cylinders,in and out of gear, the compression test is not as encouraging, starboard bank 90,35,85 port side 89,85,74, what next? can't really afford an engine rebuild right now, can it run like this? also changed the fuel water seperator, it was filled about 50/50 water and gas and alot of sediment

 

[SparkieBoat]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

whoa doggie...that 35 aint gonna cut it...that 74 is kinda low also. you need to find out why such low compression. pop off the head covers..will it run??..maybe..go faster than 7 mph??.. probably not

 

[metriccrescentwrench]

Re: 1988 johnson 175hp, doesn't accelerate over 7 mph

Did you do the compression test warm or cold? It's been my experience that the numbers vary more when you do the test cold, that may explain everything except the 35.