1987? 90hp tower of power mercury bogs out when in the water

[james shilling]

hello, I have a tower of power, starts, runs perfect in driveway on water hose,can idle and rev engine. However, when I put it in the lake it fires up and will only go about 5mph then when try to give it more throttle it bogs out and will die. I can drive around at 5mph but its a ski boat. please help!

 

[Chris1956]

Did it just start to do this? If so, the idle passages likely got clogged over the winter. You will need to clean the carbs and install new gaskets. Inspect the floats and inlet needle and seat for wear and replace all that need it.

If the carbs were serviced, and you now have this problem, it is likely the idle mixtures are set too lean for acceleration.

 

[james shilling]

thanks chris for the info. I will go more in to detail now. First off, I had starting issue, after much troubleshooting I had discovered that when I pulled the wiring harness boot off there was a broken pin to one of the wires inside the harness. I do not recommend the next step unless your stuck way out in the water! Well I took a old drill bit that was similar in size to the post and screwed it into the end of the plug where the broken pin was found, also packing the sides with tinfoil. I reassembled plug & boot and made it to shore (wouldnt mcgiver be proud of me) smile! The next day I purchased a brand new wiring harness(aftermarket) CDI is the brand name I believe. Followed all steps, also discovered another pin was previously removed or missing, I believe this pin to be the brown tachometer wire, my guages were not hooked up when I bought the boat last year so I figured that is the reason. Like I have said before . . . the engine seems to run okay at idle a little slow perhaps but will rev up and go into gear and has horspower while hooked up using garden hose and baffle. But when I take it to the lake it has no power at all just perhaps 5mph and will bog out when given throttle. I reasoned fuel pump problem, checked it out and found lots of sediment in screen. cleaned and installed an inline fuel filter. still same problem checked fuel pump again this time looking at membrane for holes. nothing found. it could possible be the carbs but why does it run perfect in the driveway but not under a load in the water? I did check a red and white jumper wire and disconnected it for i try, would not start, reconnected and still same issues.

 

[mfkadz]

Are all cylinders firing? Easy test is to pull plug wires one at a time to see if it makes a difference. You should be able to tell if pulling a wire makes a diff. You might want to shut the motor off between changes. Or, if you like juice. There's plenty to be had handling spark plug wires when the motor is running.

mike

 

[Brooky]

I'd give it a healthy dose of seafoam first.

 

[Chris1956]

OK, lots of sediment in the strainer? That strainer is the only thing keeping the crap out of your carbs. My bet is that the junk did make it to your carbs idle circuit.

 

[james shilling]

hello again, thanks for the wide variety of information. After much more troubleshooting, I mimicked the same conditions as being in the water. I than had the inclination to pull of a shroud cover. I had noticed a water leak at the top of the engine when at one quarter throttle. It turns out that there is a gasket leak in the cooling cover/pan I equate this to being similar to a blown head gasket, just that its in the water jacket part of the engine. What is happenning is that when given the throttle the water pours out the leaking gasket and then splashes all over the spark plug wires and the distributor, this I am sure is causing a short and is the reason for all my problems. Once again I will note that the engine runs perfect when started in the driveway, but when put in the water I have all the problems. Tomorrow I will attempt to pull the cover and re-gasketr and seal it. Hopefully my problems will be solved, I did notice that there are some screws way down under the cover, do you have to dimantle alot of stuff to be able to get access to these bolts, or is there an easy way to remove the bottom cover?

 

[Chris1956]

The water jacket over the head of the motor is simply a water jacket. The head is not removeable, and cannot leak compression, unless the block is cracked. I therefore doubt that is your issue. Dry out the area of the leak and smear some silicone on it to stop the leak and do more troubleshooting. Carbs are far more likely to be the issue.

 

[Chris1956]

BTW - if that motor has a distributor, it is early 1979 or older. Check the spark plug wires for arcing to ground.

 

[james shilling]

okay, problem still not fixed, i started it in a garbage can of water, ran fine for a bit, then noticed the gasket maker goo was starting to buble up. did not leak though. But than I noticed that the motor quit peeing, and only staem coming out of motor. Does this mean that the impellar inside the motor is not spinning to push the water up into the engine? How do I go about repairing that, or testing it?

 

[racerone]

The motor only sounds fine on a hose.--It will run nicely on 4 of 6 cylinders.----Do a compression test.---See if all 6 leads have spark that will jump a gap of 3/8" or more.---Replace the impeller if you do not know how old it is.---Lower unit comes off after removing the nuts ( 5 of them ) and a hidden screw under the trim tab.

 

[james shilling]

thanks for the info will try that in the next couple days.

 

[james shilling]

thanks for the help, i did replace the impellar, was really bad. went to lake with high hopes that problem was resolved. However,I was used to squeezing the bulb alot to prime engine to start, but as stated previous;y I found sediment in the fuel pump strainer. Well when I fired up the engine I had a fuel fire ! Grabbed 1 of the 3 fire extinguishers and was not smarter than a 5th grader because after pulling the pin I could not get the extinguisher to work. Threw it down and unpluged fuel line, and proceeded to splash water on the fuel fire in the outboard!!!! went home very sad, tried to start it and nothing, spent last 2 days resolving all those issues. TODAY< got the engine back on the lake and started, no fire LOL !!! I am still stressed ouit over that ordeal!! Well, to my demise I am still back at square one, sme original problem starts, idles, but when put in gear the boat goes only 5mph, When given more throttle it will bog down and die without any acceleration. I will look at the carbs in the next few days, I have read in other posts people seeming to have similar issue and turned out to be the high speed stator windings? any thoughts?? thanks!

 

[Chris1956]

The high speed stator windings kick in at about 2000RPM, so you likely have a carb issue.

Gee, I think you need to get that sediment out of your fuel tank, or use portable tanks until you get that sediment out. I would clean the carbs and adjust the idle mixtures to restore acceleration.

 

[james shilling]

thanks chris, I am just confused about the carbs. the boat revs to high rpm like it should when given the throttle on the hose. However when in the actual water it goes maybe quarter throttle then bogs out and will die if given full throttle. The fuel line when I took apart the fuel pump and inspested the diaphram for holes, I also installed a disposable in line fuel filter which it never had before. I believe this will eliminate future fuel contaminants. Since I can run the carbs on the hose in the driveway, would it make any sense to make up a concoction of fuel , seafoam and acetone and let this run thru the carbs to try to clean out, or do you suggest just taking carbs off the boat and clean than reinstall? thanks

 

[james shilling]

in addition, I did try to pull a spark plug wire off and see how it would run and when I removed a plug wire boat would not start, even tried removing other wires and still no start. Do you recommend I remove the plugs and hook up to wires and than tape plugs to grounded frame and look for 3/8th gap spark when turning engine over?

 

[Jhoppy]

The motor only sounds fine on a hose.--It will run nicely on 4 of 6 cylinders.----Do a compression test.---See if all 6 leads have spark that will jump a gap of 3/8" or more.---Replace the impeller if you do not know how old it is.---Lower unit comes off after removing the nuts ( 5 of them ) and a hidden screw under the trim tab.

+1 checkcompression check spark on all cylinders will jump 3/8 gap

 

[james shilling]

hello again,today I hooked up a inline spark checker to each plug,all appeared to be firing and sparking. I did just look at the manual I just purchased and it shows a fuel filter inside the top of the carburater, I will take this apart tomorrow and I think that has to be the problem as I found alot of varnish sediment in the fuel pump strainer. will also get a carb rebuild kit too! My boat has became my new mistress,she loves to spend my money! smile.!!!!

 

[Chris1956]

Fuel filters on top of the carb bowls were used in the early 70s. If you have those, either you have battery/coil/distributor ignition or some sort of Frankenmerc. That is not a big deal, but you want to know it so you can source parts properly. Each carb cover will have a cylinder-shaped paper filter and a rubber gasket. Change these out and then rebuild the carbs to get that pesky sediment out. More modern carbs will have a simple stainless screen under the brass fittings in the carb covers. You might clean those as well.

 

[james shilling]

thanks chris, took a look at carbs found 2 of the 3 carbs has floats with severe cracks will replace all 3 floats. Also found top carb spark plugs to be oil fouled. suspect this to be the problems. will try to fix them today, I did not find the strainer filter in the carbs, I guess mine is newer type, I do remember seeing the brass fittings will look inside those for a screen and clean, my boat does have a distributer.