I have a 6.5 Lifan (chinese clone) on a home made longtail. Took it for the first run this weekend and no matter the water depth as soon as the prop is submerged its starts bogging down. It can only run under water at WOT otherwise the load kills the engine. I know its running too deep and i need to fab some trim tabs on the cav plate. Its running a 7x4 hill prop now or at least that is whats etched on the prop. Its measures right at 7" tip to tip. It runs like a raped ape out of water.

I bypassed the gov more or less to keep it from bouncing off the gov at WOT. I dont have a tach on it yet but just from sound alone im guessing less than 1000 RPMS based on previous motors ive owned.

I know a 6.5 isnt an animal by any means and isnt a speed demon. Had it on a momarsh fatboy dp and top speed was 4.6 gps.

I know that the coil/plug wires are in bad shape and pretty chafed but i would think that would hinder the out of water also.

Exhaust lash set at 3 thou and intake at 2 thou per manual. Plug looks like coffee.

as soon as the video loads ill attach it

Unhook your low oil warning switch. Sounds like the culprit.

it doesnt kill the engine at WOT just bogs it down. At idle it will kill the engine. It rides pretty level so i dont see the oil sensor giving me that much of an issue. Right nwo im leaning more towards the coil, but it still runs great out of water

Too much load on the engine. Either too much prop, or you have a lot of valve leakage or losing losing compression. It doesn't take much power to rev an engine with 0 load on the unit. I would leak test the engine and see where the issue is.

already have,% 12-15 and still well in the green on my gauge. pretty even split between valves and crank case on leakage. Could improve my numbers some with a decent valve job.

Im wondering if that 7x4 is too much for the 6.5

Go devil uses a 7x5 on the 6.5's. You need to verify the issue. Is the governor allowing the throttle to open fully?

you can reach the rev limit with very little throttle openend with 0 load on the engine.

When you have no load / weight / outside forces acting on the motor (out of water) - it should rev up until the valves float or the governor engages. It shouldn't take full throttle to make this happen. The 6.5 honda clones should move it better than 4.6mph. My stock 212 predator moves a 14x42 with 500lbs + in the boat 12+


You may want to revisit your valve lash. Make sure you are at top dead center. The cam likely has a a compression release to make pull starting easier.

Turn the crankshaft the correct direction, and watch as the intake valve will close as the piston rises. Just before the piston reaches "top dead center" - you will see or feel the exhaust valve bump open. Roll the engine a few more degrees and you should be ready to check your valve clearance. You should do this with the engine cold. With your thumb and finger rotate the push rod as you tighten the adjuster down. Tighten it until you cannot turn the push rod. Back off a few degrees until you can turn it again. Lock it down with the lock nut. Check push rod again.

Exhaust opening (set intake), Intake closing (set exhaust).

This is movin at the BLAZING speed of 4.5mph.... gps

https://youtu.be/ggh4j7ZkPPc

What do you all think?

ive noticed that unless its a 35hp, kawasaki, prodrive, GT thread they get pretty overlooked in the motor section.

It's not necessarily being overlooked, it's just not an engine most of us have direct experience with. Yes, it sounds like a combination of fuel, prop, and compression loss due to valves or rings. It could be all, any, or none of the above, though. It's a 6.5 hp engine. There will be more noticeable difference between engine running perfect and something not right than if that happened on a much larger block. Troubleshooting over the Internet is not nearly as simple as it might seem when you consider different communication styles. You say you've done A, you think we understand exactly what you've done, but you might have missed one thing we consider is implied with task A. We also make some guesses that you've done certain checks as you are experienced, but if you havent, then some of those could be the culprit (air leak somewhere, fuel not flowing to the carb very well, etc). There is a lot more experience on this forum related to engines 20hp and over, and most of us don't want to send you down the wrong path on an engine we've never dissassembled.

Mechanical gov with a different spring could be closing the throttle more on top keeping you from revving as high as it could in water.

Set valves the correct way. That 1/4 past tdc is pretty easy to screw up and leaves little to no room for error. Probably not your issue, but worth a shot.