98' 40HP loss of power...limp mode?

[Euroshowoff]

Recently just had the issue happen two weeks ago while out on the water. Summer maintenance included w[FONT=Roboto, arial, sans-serif]ater pump impeller/gasket replacement, new plugs, and new battery. Also siphoned out all the old gas, re-filled with fresh gas and added some fuel treatment to the mix. Boat idles and runs fine while on muffs, I ran it in short bursts and see over 5K rpms. However when I hit the water at WOT i'm only topping out at 2800-3000 rpms and the boat will not plane. No surging, idle's fine, does not feel like it is being starved for fuel. [/FONT]

[FONT=Roboto, arial, sans-serif]I did go into an overheat alarm many weeks back because of some weeds that clogged the water port, stopped the boat, cleared the debris and the motor doesn't alarm anymore. [/FONT]

[FONT=Roboto, arial, sans-serif]Any help will be appreciated, can't really travel to any fishing spots, just using trolling speeds atm. [/FONT]

 

[pnwboat]

Start by verifying that you have spark on both plugs. Check compression too. If squeezing the primer bulb while underway temporarily fixes the problem, then you might want to replace the fuel pump diaphragm.

 

[Euroshowoff]

what is good compression for this motor?

 

[pnwboat]

You should see a minimum of 125LBS or so on each cylinder. It can be lower and still run reasonably well but the higher, the better. More importantly the reading should not vary more than 10% between the two.

 

[Euroshowoff]

i managed to pick up a compression tester from harbor freight. Cylinder one = 135 and cylinder two = 125. I did notice that the spark plug for cyclinder 2 was really loose.

 

[pnwboat]

Well that's a good sign. Next would be to make sure you have good spark to both plugs. It's hard to say if the loose plug was the cause of your problem, but it certainly should be tight.

 

[Euroshowoff]

How would I check for good spark? I did recently replace and tighten all plugs. Boat still does not want to move at wot

 

[ondarvr]

And do not rev the motor to 5K on the hose, you may not like the results.

 

[Euroshowoff]

Yes - thanks I did read that it is not recommended.

 

[Euroshowoff]

turns out that I am not getting spark in the top cycliner. bottom plug fires without issue.

 

[Euroshowoff]

Attempted to swap harnesses to see if the issue follows. When I swap connector to the top coil pack there is no spark. However if swap the harness from the top to the bottom coil pack I also get no spark. The only config that I am seeing spark is on the bottom cylinder with the bottom harness plugged into the bottom coil.