50TLRD acceleratoin problem and Yamaha's response

[margaritaville]

I have had an ongoing issue with a 2005 50 TLRD, after a rebuild and new carbs, the engine was broken in again.

Late last year, the engine developed an acceleration problem. From and idle with the engine tilted all the way down, the engine would bog down if the throttle was slowly advanced.

Yamaha looked at the engine and said it is because the engine is tilted all the way down and when in that position, the engine head is not level. It is causing the yamalube to pool up on the piston head and causing the bogging issue.

Anyone have any thoughts on this? Sound like a bunch of crap?

[boats.net]

I havn't had any problems with oil puddling on the 50TLRD engines.

[margaritaville]

I havn't had any problems with oil puddling on the 50TLRD engines.

It is mounted on a 16' Lowe john boat. There is an angle on the stern, but it does not seem excessive.

Yamaha has had one excuse after another on why the engine won't run right. It is always the fuel, but when they take the fuel out of the equation the problem has always still occurred.

The problem stated in the first post is just the latest in a serious of issues over the last 2 + years. When the motor is slightly trimmed up the problem does not occur.

I am thinking some type of gasket leak in the carbs or the float is stuck.
They have had the carbs on and off the boat so many times, I have lost count.

[margaritaville]

I had a marine surveyor run the boat yesterday and he did some tests.
The engine really never really got up to temp even after running it for two hours.

Water temp was 45, but would that alone keep the head to only get to 105*?

Cold there be something wrong like a thermostat bad that is causing the engine to run cold and the electronic choke to kick in and bog the engine down?

[boats.net]

You can check to see if thermostat is stuck open. The Prime Start(choke) system on that engine is temp related. When engine is cold the primer solenoid plunger contracts allowing fuel to pass by, when engine starts voltage is applied to solenoid causing it to heat up and extends plunger down closing off fuel passage(removing choke). You can bench test primer solenoid by measuring plunger when cold and then applying 12 volts to primer and remeasure plunger after 5 minutes to see if moved.

[margaritaville]

anyone wants to see the engine stall out, I have a small video. This engine was run for 1 hour, the temp of the head was 105*

http://www.cossaboon.us/barn/50hp%20...ha_problem.avi

The file is in DIVX format. it should play for most people, but if it does not you can download a free player at
http://www.videolan.org/vlc/download-windows.html

VLC player is a free program and is spyware free.

Maybe hearing the engine might get one of you guys on the right track

[boats.net]

I couldn't tell much from video, I could only get sound no video. Assuming that the pistons, rings, seal rings, all seals and gaskets are installed ok in engine. You might check the recirculating hoses are installed correctly and check valves are ok. There may be a cap missing from low speed jets in carbs or loose jet, carbs out of sync, bad diaphragm in fuel pump, seal leaking on back of oil pump. The possibility's are endless.

[margaritaville]

You wouldn't see much from the video, the sound is enough.

Unfortunately, Yamaha is sticking by their statement that there is nothing wrong with the motor. The oddest part of the issue is that the problem is worse when the motor is tilted all the way down. When it is trimmed slightly, it seems to be a little better.

Not sure if it is the angle or the lessening of the load on the engine that is making the difference.

[captflossman]

Get a vacuum gauge for your carbs and see if they are in sync. I would pull the carbs and check all of the lines to them for clogs and check floats. If they have recently been rebuilt then you can reuse the gaskets if you are careful.

[margaritaville]

Get a vacuum gauge for your carbs and see if they are in sync. I would pull the carbs and check all of the lines to them for clogs and check floats. If they have recently been rebuilt then you can reuse the gaskets if you are careful.

What should the vacuum pressure be on these carbs?