I have a 1998 Mercury 225 EFI that bogs down severely under load. The boat (1998 Nitro 912) will not plane out. This problem began to develop just recently. When it first started I could have whoever was with me go towards the front deck and the boat would gradually climb out of the hole and run just fine once on-plane.<br /><br />The motor idles fine. It just will not gain any power past 2000 - 2100 RPMs. I have confirmed that each cylinder is getting fire. I have replaced all of the spark plugs. I have checked the gas for water or trash (none found). I have also verified that the compression on each cylinder is good (approx. 100 lbs, each cylinder).<br /><br />Any help would be most appreciated.<br /><br />Also, I have read other articles that state testing "spark strength" for strong blue spark is important. I am not sure how to do this. The only spark tester that I have is an old pen-type device made by Champion, that when held to the plug wire will verify spark being present. I was curious as to how you correctly identify "spark strength".<br /><br />Please excuse my ignorance.
<br /><br />Also try this...<br /><br />Have someone along with you, squeeze the primer bulb as you are trying to accelerate and see if this allows engine to run normal. (Primer bulb should remain hard once primed and engine running.)<br /><br />If it runs normal while squeezing the bulb, replace the primer bulb.<br /><br />Hope this helps.