!987 85 hp no top end

[walleye jr]

heading bac to harbor other day ....cruising along at 32 mph 4800 rpm and all of a sudden blah ....couldn't get more than 3000 rpm ...took to shop cked compression all good adjusted floats changed fuel quick disconnect took it out ran iot same thing 300rpm , ran smooth no miss no hic ups just no top end rpm . took back to shop rebuilt all three carbs ....same thing ...mechanic at shop is stumped .. hes been doin this for 40 plus yrs .....last tank of gas i added a can of c foam to tank and religiously put ethanol additive in gas .....thoroughly stumped help

 

[Tassie 1]

There is no mention of a spark test in your post,

was that done too?

 

[walleye jr]

compression and spark test .....was done boat ran in tank for a couple of hours with out any temp issues

 

[jerryjerry05]

Any fuel coming back through the carbs?
Remove the plenum and watch it as it runs?
Plugs burning right? center one wet? check the fuel pump diaphragm.
Check the throttle linkage and make sure it's advancing.
When you cleaned the carbs did you make sure the jets were clear? soaking won't remove a clog.

 

[walleye jr]

havent had a chance to run it any more taking it to a marina where they can actually take it out and run it ...carbs were rebuilt by a so called reputable shop but just ran in tank .... wasnt impressed by his comments ...." u need to give me more info" and i dont kno i dont want to waste my time and ur money by just changing parts ......so i just payed him for what he did ....wasnt impressed ...and he didnt offer to take it out in river and run it to see whats goin on ....hence ill never go back

 

[foodfisher]

Check plastic connection at the top of the timing tower. Mine looked good but the threads where reamed out.

 

[walleye jr]

just double cked fitting top of tank was told there is a ck vale there mine is straight pipe also cked to make sure fuel line will siphon which it does ......so i think alls thats left would b timing tower as mentioned a coil pak and possibly a fuel pump ? ..

 

[Jiggz]

To clear off the fuel delivery issue, install a clear fuel filter between the fuel outlet and the carbs' inlet. This should always stay full or at least 1/2 full at WOT. It doesn't have to be a complicated one. Just a simple Fram G2 will do and costs less then $5 each. This is more for troubleshooting than actual filtering.

Of course, check the timing tower or tower shaft also. You can do this without running the motor. Remove the cowl cover, have someone shift the throttle control slowly to forward (if it would not engage manually rotate the prop) and then all the way WOT. Keep watching the timing rod move the trigger plate and then also watch the cam follower moving the carb linkage on all 3 carbs.

Keep throttle handle at WOT, remove the carbs' air cover and then check make sure all throttles are at full horizontal.

 

[jerryjerry05]

If you have someone using the throttle when the motor's not running you need to spin the prop.
The linkage can bind and break if the props not moved.

And that G-2 filter does keep the tiny cruds out of the carbs.

Top of the tank check valve: on the outboards there usually isn't a valve.
The anti siphon valve is used on inboards and I/O's