Hi folks,
Brand new to the forums and spent a good deal of searching Google for possible fixes before I finally came here. I have an old 1981 Mariner 15HP 2-Stroke (Japanese made, 684CS 013799 badge ID. 50:1 gas mixture) that hasn't seen much use the past couple years but has always run like a champ. It came with 16' Jon Boat that I bought 5+ years ago and I've never done much to it other than new plugs (BR7HS gapped at .024) and running it dry before putting it away for winter. It's always fired up perfectly when I bring it out for the summer with new gas.
Here's some recent history on my troubles this year. Last year, mice got under the cowl and built a nest. Forgot to stick some steel wool in the opening, mea culpa. Once all the debris was removed I noticed they chewed a couple things. Nothing major that I could tell. One was the fuel line coming into the fuel filter. The hole was so tiny, I used a bit of gasket maker over it, let it cure for a day, and wrapped it in electrical tape. It started, seemed to run ok but when I give it gas to accelerate in forward gear, it is slow as molasses in the water. I neutral, it seems to rev really high.
So, thinking maybe it was a vacuum leak in the fuel line that was chewed, I replaced it with new fuel line and even replaced the fuel filter as it was the original from 1981. I though it might also have been the fuel lines from the gas tank having gunk or blockage in them but when I squeezed the primer bulb, the fuel filter filled up without issue. I also replaced the lower unit oil (SAE90) as some other forum suggested it might be that. I also looked at and adjusted the throttle cam to make sure it was fully opening the carb and it is wide open. Just doesn't seem to want to go fast at full throttle. Prop is original to the boat, on tightly and has never had an issue getting us up to speed the past 4 years prior. I replaced with new BR7HS plugs but it made no difference either.
Just tested the motor again today and it was slow as molasses. Fuel is new 87 octane and was properly mixed at 50:1 with marine grade 2-Stroke stuff. The blue color stuff, not green. If it makes any difference, idle in neutral is mostly ok. Idle in forward will usually stall out unless I give it some gas. Reverse seems to be fine but like forward gear, will stall out if it doesn't have some gas. My hunch is that there's a blockage in the carb but I am not a small engine or outboard mechanic.
Hoping someone out there has some insights into what else I might need to look at.
Brand new to the forums and spent a good deal of searching Google for possible fixes before I finally came here. I have an old 1981 Mariner 15HP 2-Stroke (Japanese made, 684CS 013799 badge ID. 50:1 gas mixture) that hasn't seen much use the past couple years but has always run like a champ. It came with 16' Jon Boat that I bought 5+ years ago and I've never done much to it other than new plugs (BR7HS gapped at .024) and running it dry before putting it away for winter. It's always fired up perfectly when I bring it out for the summer with new gas.
Here's some recent history on my troubles this year. Last year, mice got under the cowl and built a nest. Forgot to stick some steel wool in the opening, mea culpa. Once all the debris was removed I noticed they chewed a couple things. Nothing major that I could tell. One was the fuel line coming into the fuel filter. The hole was so tiny, I used a bit of gasket maker over it, let it cure for a day, and wrapped it in electrical tape. It started, seemed to run ok but when I give it gas to accelerate in forward gear, it is slow as molasses in the water. I neutral, it seems to rev really high.
So, thinking maybe it was a vacuum leak in the fuel line that was chewed, I replaced it with new fuel line and even replaced the fuel filter as it was the original from 1981. I though it might also have been the fuel lines from the gas tank having gunk or blockage in them but when I squeezed the primer bulb, the fuel filter filled up without issue. I also replaced the lower unit oil (SAE90) as some other forum suggested it might be that. I also looked at and adjusted the throttle cam to make sure it was fully opening the carb and it is wide open. Just doesn't seem to want to go fast at full throttle. Prop is original to the boat, on tightly and has never had an issue getting us up to speed the past 4 years prior. I replaced with new BR7HS plugs but it made no difference either.
Just tested the motor again today and it was slow as molasses. Fuel is new 87 octane and was properly mixed at 50:1 with marine grade 2-Stroke stuff. The blue color stuff, not green. If it makes any difference, idle in neutral is mostly ok. Idle in forward will usually stall out unless I give it some gas. Reverse seems to be fine but like forward gear, will stall out if it doesn't have some gas. My hunch is that there's a blockage in the carb but I am not a small engine or outboard mechanic.
Hoping someone out there has some insights into what else I might need to look at.
