1988 Mercury 70hp

[fishingtomatoseed]

i have 88 ray craft 16' w/70hp mercury. it is real slow out of the hole. it idels real rough and is hard to put into gear w/out it dieing. also when you do get it to plan out at full throttle it is only runing at maybe 2500-3000rpm and after about 5min. of running it dies. like some one just shuts the fuel off. the warmer the motor gets the the more it acts up. just got the boat and whant to fish. Thanks for any feed back.

 

[mellowyellow]

Re: 1988 Mercury 70hp

welcome aboard <br />is this a new motor for you? have you done<br />any maintainence on it? if you don't already have<br />a manual, get one (bottom left of page or local<br />library) and perform prescribed maint.<br />when was water pupmp impeller replaced last?<br />also sounds like the carbs need to be removed<br />and cleaned and a new kit installed. would also<br />reccomend a compression test.<br />good luck,<br />M.Y.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

thanks mellowyellow <br />yes this is a new motor for me. i also have a 75 20hp merc. for bowfishing and never have a problem with it. what is the compression test for? busted rings or just wear. also could it just be proped wrong.thanks

 

[Trent]

Re: 1988 Mercury 70hp

First check for spark at all three cylinders. If its their then do a compression check. Sounds like a dead cylinder. I personally have this same engine on one of my boats and they perform well.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

thanks trent<br /> also i have read here that some people take the oil inj. off and just mix the oil. is this and good thing to do or just leave it alone? on the problem with it just quiting at f/t on plane could be running out of gas, getting to hot and locking up,or power packs. but at 3/4throttle you can run for a long time.

 

[mellowyellow]

Re: 1988 Mercury 70hp

could be a number of things causin yur problems.<br />if I were you, I would start with spark test also.<br />start it up and pull off one plug wire at a time.<br />if there is no change when a wire is pulled, then<br />that is a dead cylinder. be careful or you'll get<br />zapped good! <br />if spark is good, we'll move on to carbs.<br />are you running fresh gas or old?

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

when i first got the boat i drain the gas and have been running fresh gas. i have replaced the fuel line and bulb. what is the best way to clean the carbs. taking them off and soaking them or someone was telling me to get somthing that you sprayed into the carbs. do yall think this is a minor of major problem? thanks

 

[Trent]

Re: 1988 Mercury 70hp

Best way is to remove the carbs and tear apart and install a kit. Use plenty of spray carb cleaner. <br /><br />I personally removed my oil injection and capped off the line from the oil tank at the fuel pump and removed the oil pump gear and oil tank. As old as the 1988 model is I dont worry about it.

 

[jim dozier]

Re: 1988 Mercury 70hp

Just to add to Trent on the spray cleaner. The spray cleaner is OK if you have removed the carb and disassembled it. It is probably useless to spray it in the throat or on the outside unless you just want the carb to look pretty.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

thanks trent<br /> i will try all the ideas and wee what i come up with. and let yall know. i think i need to go work now.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

thanks jimd<br /> have yall seen or know much about the boat ray craft. i have not seen or heard of them.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

alright this is the first time that i have started the motor with "ear-muffs" on. So this is the first time that i have listen to the motor that close. I pulled the spark plug wires off one at a time and you could really tell the difference each time, but with it just ideling you can hear a some what hard knocking sound. I am going to geuss that ain't good. so what do yall think. thanks

 

[Trent]

Re: 1988 Mercury 70hp

 

[Trent]

Re: 1988 Mercury 70hp

Im not their to hear it but mine is real noisy out of the water.<br /><br />Check the compression. If over 100 psi and all within 10-15 percent of each other. Do the carbs.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

thanks trent<br /> hope that the motor is ok. i will check the compression on it and go from there.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

good afternoon <br /> well i check the compression and:<br />Top:120<br />Middle:120<br />Bottom:100<br /> Is this Ok thanks for all of the info already

 

[Trent]

Re: 1988 Mercury 70hp

Id run it. Bottom a little low but it may come up. Do the carbs.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

Thanks everyone for all the information. I will do the carbs. and run it.

 

[mellowyellow]

Re: 1988 Mercury 70hp

agree with carbs, but also install new water<br />pump kit and fuel pump kit. you can also try<br />to de-carb it and maybe get the pressure up a bit<br />but readings are not that bad. new lower unit oil<br />and your good to go.<br />good luck,<br />M.Y.

 

[fishingtomatoseed]

Re: 1988 Mercury 70hp

is installing a water pump just a standered thing to do. it's so cheap why not type thing.thanks again.