1982 Mariner 175HP wont accelerate once in water

[cdoelling]

Motor starts fine, idles fines but sometimes when taking off, motor will not accelerate. RPMs come up some but boat wont take off. Ive noticed a couple times when turning left and right engine will take off. Ive tried pumping primer bulb when throttling up but no difference. Seems to throttle up fine out of the water using muffs.​

 

[flyingscott]

Compression and spark test need to be done. In that order

 

[cdoelling]

Compression was around 120 on all cylinders. I know it had spark on all cylinders, does voltages (amount of spark) change with engine RPM?

 

[Tassie 1]

Info given is a little vague and sparse,
As well as the above advice,
check for spun prop hub,

how high do the revs go?
withthe boat still in the water give the throttle a good squirt,
does the motor maintain revs itself or gradually bog down?

finally, is the boat full of water, under the floor?

 

[cdoelling]

How do I check for spun prop?

RPMs only come up to about 1500 even when throttle is wide open. You can hear every once in a while that the RPMs start to come up and bot picks up a little speed but then goes right back to about 1500. Motor doesn't sound like its missing or anything just wont kick in and take off.

A couple times yes the boat had lots of water in bottom.

 

[444]

My 1978 175hp would throttle up fine on the muffs but not to over 1500rpm in the water. I tried a bunch of different things and eventually all it needed was a link and sync. In neutral, when you hit the throttle the carbs don't actually open, the ignition timing lever advances and throttles it up.

 

[cdoelling]

Thanks for the reply!!!! How do I do a link and sync??

 

[Tassie 1]

Top of the engine repair section there is a faq section,
page 2 first topic,

 

[cdoelling]

Updated info.... The problem used to be only every once in awhile but not is more consistent. To elab on the problem a bit more....
In the water.... Engine idles fines, when I give it throttle, motor RPM comes up some (1500 ish) so I keep giving more to full throttle but RPM never goes up anymore. Boat only gets up to about 10mph, engine even at full throttle sounds fine just like its at 1/4 throttle instead of full. I can see all the linkage and carbs going full but no power. Tried squeezing primer whole time but no difference. It also seems that if I try a S pattern in water RPMs sometimes (coincidence??) start to come up. Can there be too much water getting into motor (gaskets leaking, ect) and exhaust wont push enough out??

In my yard on muffs, same sequence going to full throttle (I never go that far on muffs, just rev it up some) RPMs follow throttle and everything seems fine.

 

[444]

The on the in faq is for the inline engines. I recall the process from my V6 being a little different. Of note, the idle mix on the v6's is not adjustable. I have the clymer service manual for my V6, the instructions were all in there. After a few wasted trips to the lake, I have decided that for my junk any time a carb is removed it's best to do a full link and sync. I would pull the carbs, clean them, check the float height and replace the mounting gaskets.

Also, check your bleeder lines that criss-cross the powerhead, on mine they were half disintegrated so I replaced them all. That won't be your problem but a good idea to check them while you're there.

 

[Tassie 1]

The on the in faq is for the inline engines.

Correct.
my mistake.
having a 175 merc here l should have actually read a few lines first before mentioning it

 

[cdoelling]

Link and sync didn't work....

Updated info.... The problem used to be only every once in awhile but not is more consistent. To elab on the problem a bit more....​

In the water.... Engine idles fines, when I give it throttle, motor RPM comes up some (1500 ish) so I keep giving more to full throttle but RPM never goes up anymore. Boat only gets up to about 10mph, engine even at full throttle sounds fine just like its at 1/4 throttle instead of full. I can see all the linkage and carbs going full but no power. Tried squeezing primer whole time but no difference. It also seems that if I try a S pattern in water RPMs sometimes (coincidence??) start to come up. Can there be too much water getting into motor (gaskets leaking, ect) and exhaust wont push enough out?? ​

In my yard on muffs, same sequence going to full throttle (I never go that far on muffs, just rev it up some) RPMs follow throttle and everything seems fine. ​

 

[444]

Did you pull the carbs, clean then, check the float height and replace the carb base gaskets before doing your link and sync? If not, I would start there, then do the link and sync again and change all your fuel filters to make sure you don't have any kind of fuel restriction.

 

[Faztbullet]

What kind of hull and what pitch prop???