Mercruiser Pre Alpha Drive Trim Restriction Blowing out seals

[seasaw63]

Hi, I am having trouble with my 1978 23' Sportscraft Inline 6 outdrive trim system. The trim system is a Pre Alpha Prestolite system (high-pressure low volume). I have replaced many parts of the system and I am getting nowhere. I have bled the system, replaced the trim pump, valve body, and valve body line block (Mercruiser new NOS). I have taken off all of the lines and blew compressed air through them as well as the hose manifold block. I have removed the trim cylinder hoses and the drive moves up and down freely. When I put everything back together the pump stops and blows things like the reverse lock cap and the plastic line that goes to the reverse lock. I am going to pull everything out of the boat and assemble it on a table for easy access for further diagnosis. I would love to have a merc. pressure gauge (650.00), but I am $1000.00 into this problem and still at ground zero. I am hoping there are some old-school Mercruiser people out there that could help. I am skeptical that I have the right new valve body, but I don't know. It is a little different than the original, the dealer insists that it will work.
Thanks for any help in advance,
Steve

 

[kenny nunez]

Post a picture of the hoses between the lower block to the rams.
The hoses go front of the block to the furthest port on the rams, these rams are not left and right so always use the front port on either ram. Is the hoses connected to the block where the high pressure port is forward?
Have you had the rams apart? It is possible to have them assembled wrong with the steel check valves backwards. Hope this helps.

 

[Bondo]

but I am $1000.00 into this problem and still at ground zero.

Ayuh,..... Welcome Aboard,....... Havin' gone through this years ago, I found the cure was to ditch all of the plumbin' between the hyd. manifold under the transom housing, to the pump, 'n buy a current model pump, 'n lines to the hyd. manifold,.....

Never had a trim problem after the switch,.....

 

[Bt Doctur]

that or you have 2 trim lines reversed depending on your cylinders and the hoses both rear hoses to the rear of the manifold block. With 1 front and 1 rear your "shorted" together

 

[achris]

What is a ‘Pre-Alpha’ drive?

What is a ‘Pre-Alpha’ drive? We see this all the time…. I have a ‘pre-Alpha’ drive, can you tell me…..??? What parts do I need for my ‘Pre-Alpha’? And so on…. Before anyone can answer those questions, we need to know, exactly WHICH ‘Pre-Alpha’ drive do you have? Mercury never produced a...

forums.iboats.com

 

[seasaw63]

Post a picture of the hoses between the lower block to the rams.
The hoses go front of the block to the furthest port on the rams, these rams are not left and right so always use the front port on either ram. Is the hoses connected to the block where the high pressure port is forward?
Have you had the rams apart? It is possible to have them assembled wrong with the steel check valves backwards. Hope this helps.

Hi Kenny, thanks for the response. I will post a picture of the lines coming from the manifold. I marked the lines before removing them and double-checked the manual. the line set up is front of the manifold (fore) to front of the piston and rear of the manifold (aft) to the rear of the piston. I did rebuild the pistons about ten years ago. I'll be going to the boat on Monday and post you a picture.
Thanks again

 

[nola mike]

What is a ‘Pre-Alpha’ drive?

What is a ‘Pre-Alpha’ drive? We see this all the time…. I have a ‘pre-Alpha’ drive, can you tell me…..??? What parts do I need for my ‘Pre-Alpha’? And so on…. Before anyone can answer those questions, we need to know, exactly WHICH ‘Pre-Alpha’ drive do you have? Mercury never produced a...

forums.iboats.com

You're on a tear today

 

[seasaw63]

H

Ayuh,..... Welcome Aboard,....... Havin' gone through this years ago, I found the cure was to ditch all of the plumbin' between the hyd. manifold under the transom housing, to the pump, 'n buy a current model pump, 'n lines to the hyd. manifold,.....

Never had a trim problem after the switch,.....

Hi Bondo,
Thanks for the help. I have read through some older posts and saw that you and Don have just eliminated the Prestolite system and went with the updated newer trim system. I have three reasons that I would like not to have to do that. One I have about $1000.00 into trying to solve the problem (I'll post some pictures of all of the parts I have bought), two I would have to fabricate the new system to the boat (there is no room for a floor mounted system, and three I want to figure this problem out.
Thanks again for the reply,
Steve

 

[seasaw63]

that or you have 2 trim lines reversed depending on your cylinders and the hoses both rear hoses to the rear of the manifold block. With 1 front and 1 rear your "shorted" together

Hi Bt Doctor,
I am pretty confident I have the lines correct. I am goung to pull the whole system out of the boat and set it up on a table and try to figure it out.
Thanks,
Again,
Steve

 

[seasaw63]

What is a ‘Pre-Alpha’ drive?

What is a ‘Pre-Alpha’ drive? We see this all the time…. I have a ‘pre-Alpha’ drive, can you tell me…..??? What parts do I need for my ‘Pre-Alpha’? And so on…. Before anyone can answer those questions, we need to know, exactly WHICH ‘Pre-Alpha’ drive do you have? Mercury never produced a...

forums.iboats.com

Hi achris,
Thanks for the info and the lesson. Origanally the boat had a MC 1 and I upgraded it to and alpha one back in 2000, the gimbal housing is origanal.
Thanks,
Steve