I received the following advice when I asked this question last year (I ended up purchasing
a boat with a new Universal 25XPB instead):
She should start rough and blow lots of white out the back. This should clear up after a few minutes. Check the outflow and make sure she is spitting water. Black water means oil is in the system like was the case for mine- it meant the baffle hose was shooting oil to the exaust causing black dirty water that over time would cause black smoke and eventually run away.
If clean water is coming out and oil and tranny lube is good color then rev up and down in neutral. Shift in and out of gear
. IF your tied to the dock
it wont matter if you drive in to the dock
and throttle up near full load- run her full for a few minutes- check out water flow and listen to engine running for any off setting noises which would be internal problems and you SHOULD PASS. IF it sounds good and runs strong in forward and reverse for 20 minutes then idle back down and leave in neutral and then inspect visually the water and fuel pump
. If they do not know the last time the impeller or fuel filter
were changed no big concern- this can be done yourself easily on Yanmars.
Idle down to lowest load and check engine mounts. Engine should be virating pretty good knock knock knock this is normal but if mounts are loose this means you will have to take out engine and replace the support beams under the fiber glass (pass on boat) or perhaps just go a bigger gauge moutning bolts and bore deeper down (not so big of a deal)
Shut off engine after 45 minutes running and then inspect hoses- any worn hoses should be replaced bu these are cheap
and easy but make sure you make a big stink to lower asking price
. make sure not a lot of dust is present around belts which means the belts could be worn (easily replaced) or worse misaligned. If worn replace, if misalinghed I recomend you pass.
Next visually inspect the engine compartment. Is any oil leaking or fuel anywehere? Is the engine hot but not burning? 120 degrees around is normal.
is a stream of water evident from the stuffing box (not engine its self but if stuffing box is leaking AFTER engine is off could mean allignment problems and potential expensive repairs
. I recomend you dig further- when was last time stuffing was replaced? This is not big deal- if prop shaft and engine are misaligned this is big deal and you should pass.
If the engine its self runs good, spits clean water, shifts fine, runs under load without weird noises, is held fast to the mounting blocks, and is properly aligned you should not have major concerns. Buy the boat. One thing- If the engine IS vibrating a lot then it could be a fouled prop but since your boat has been on hard you wont need to worry about this unless they have a wrong prop with in proper pitch
If you do buy the boat YOU NEED TO take off the fuel pump
and check the impeller visually, take off the fuel pump and inspect/replace the fuel filter
, replace the belts, replace any suspicious hoses, and start a log of how many hours you are running on it to keep proper maintenance
Even if you do get a surveyor
this is what they will do. They will not go inside the main engine block or tranny and do anything so SAVE YOUR MONEY
AND DO THIS YOURSELF.
If THERE IS a problem inside the engine block dont waste your time- move on. Tranny is not as big a deal they can be replaced by yourself (i did mine) but you will still have to disconnect the engine and remove it from the compartment to get to the tranny which is a lot of work and time so unless you REALLY love the boat just pass- its a buyers market.