ProStreet83C10
New member
Hey everyone. This will probably end up being a long post so please bear with me as I'm new to outboards and want to make sure I'm doing things right and in correct order.
Anyway i picked up a 1994 Lund boat with a 1994 Johnson 40hp engine (j40tlere). Boat ran fine when i picked it up but it does however have low compression on both cylinders. Has approx 75 on top cylinder and approx 50 on bottom. My assumption is the head gasket is failed and compression is leaking between the cylinders. I don't believe it has any internal engine damage as scored cylinders or holes in pistons as i feel that would create a poor idle scenario. However as i said I'm new to outboards so I'm not holding myself to anything.
First thing i will do before anything else once it warms up here in Iowa is buy a can of OMC engine tuner and decarb the engine then re-test the compression and see if there's any change - i also feel the engine needs it anyway as i peeked in plug hole last fall and all i saw was black. If compression still reads low i will remove head and inspect gasket for any failed areas. Check head for flatness and have planed at machine shop if needed. Replace head gasket and retest. If still low what's next. Cylinders/pistons?
Once i get the engine sorted out (hopefully) i will go through the carbs and rebuild them whether i believe they need it or not as the boat has been sitting with presumably old gas in engine. How easy or difficult is it to rebuild carbs on an outboard? Should i do carbs before addressing the low compression?
Next I'd like to test the fuel pump/VRO pump to make sure its in working order. How does one test that to ensure its good? Does anyone offer a rebuild kit for the fuel/VRO pump as the only thing i can find on marineengine.com is the non VRO fuel pump rebuild kit.
After those three items are sorted out i plan to pull lower unit off and replace water pump. Seems like that's a fairly common piece to replace and beings i don't know current condition or length of time its been in there i feel its just cheap insurance to do.
I also feel the gear housing needs resealed as i did have SOME water contamination in there - however i don't know how many seasons the gear lube had been untouched. May run it this season and see how contaminated lube is this fall then address at that time. Replaced gear lube with AMSOIL 75w-90 marine gear lube which allows up to 10% water contamination.
I'd also like try and figure out if the VRO system is hooked up and still in tact or not. If it is id like to run through the VRO system to make sure its working as it should so I'm not burning anything up. I'm ASSUMING the system is working as the primer bulb and lines are hooked from tank to engine. I plan to run AMSOIL sabre oil in it regardless of pre-mixing or running through VRO system.
Will also perform a full tune up on boat, new plugs, wires etc. What else should be replaced on a general engine tune up? Fuel filter etc?
I'm positive there's some stuff in here i need to check that I'm missing. Please let me know what else i need to do or check/replace/rebuild etc before i put this boat on the water as i want to make sure its as close to if not 100% ready to go on water without issue/trouble expected.
I've included pictures of my boat motor, ID/serial number and lower end gear lube. Please let me know your thoughts, concerns, tips/trucks, advice, order of repair, etc so i can do all this correctly and in correct order.
Lastly if your still reading this than thank you. As i warned this would become long and i really am needing/looking for all above mentioned to do this right. I'm fairly mechanically inclined and refuse to pay someone else to do something I can do myself AND learn from doing it myself.
Anyway i picked up a 1994 Lund boat with a 1994 Johnson 40hp engine (j40tlere). Boat ran fine when i picked it up but it does however have low compression on both cylinders. Has approx 75 on top cylinder and approx 50 on bottom. My assumption is the head gasket is failed and compression is leaking between the cylinders. I don't believe it has any internal engine damage as scored cylinders or holes in pistons as i feel that would create a poor idle scenario. However as i said I'm new to outboards so I'm not holding myself to anything.
First thing i will do before anything else once it warms up here in Iowa is buy a can of OMC engine tuner and decarb the engine then re-test the compression and see if there's any change - i also feel the engine needs it anyway as i peeked in plug hole last fall and all i saw was black. If compression still reads low i will remove head and inspect gasket for any failed areas. Check head for flatness and have planed at machine shop if needed. Replace head gasket and retest. If still low what's next. Cylinders/pistons?
Once i get the engine sorted out (hopefully) i will go through the carbs and rebuild them whether i believe they need it or not as the boat has been sitting with presumably old gas in engine. How easy or difficult is it to rebuild carbs on an outboard? Should i do carbs before addressing the low compression?
Next I'd like to test the fuel pump/VRO pump to make sure its in working order. How does one test that to ensure its good? Does anyone offer a rebuild kit for the fuel/VRO pump as the only thing i can find on marineengine.com is the non VRO fuel pump rebuild kit.
After those three items are sorted out i plan to pull lower unit off and replace water pump. Seems like that's a fairly common piece to replace and beings i don't know current condition or length of time its been in there i feel its just cheap insurance to do.
I also feel the gear housing needs resealed as i did have SOME water contamination in there - however i don't know how many seasons the gear lube had been untouched. May run it this season and see how contaminated lube is this fall then address at that time. Replaced gear lube with AMSOIL 75w-90 marine gear lube which allows up to 10% water contamination.
I'd also like try and figure out if the VRO system is hooked up and still in tact or not. If it is id like to run through the VRO system to make sure its working as it should so I'm not burning anything up. I'm ASSUMING the system is working as the primer bulb and lines are hooked from tank to engine. I plan to run AMSOIL sabre oil in it regardless of pre-mixing or running through VRO system.
Will also perform a full tune up on boat, new plugs, wires etc. What else should be replaced on a general engine tune up? Fuel filter etc?
I'm positive there's some stuff in here i need to check that I'm missing. Please let me know what else i need to do or check/replace/rebuild etc before i put this boat on the water as i want to make sure its as close to if not 100% ready to go on water without issue/trouble expected.
I've included pictures of my boat motor, ID/serial number and lower end gear lube. Please let me know your thoughts, concerns, tips/trucks, advice, order of repair, etc so i can do all this correctly and in correct order.
Lastly if your still reading this than thank you. As i warned this would become long and i really am needing/looking for all above mentioned to do this right. I'm fairly mechanically inclined and refuse to pay someone else to do something I can do myself AND learn from doing it myself.