1991 force 150hp

[huck1545]

Hi Thank you for letting me join.Looking to gather some great info from this forum.My issue is that I have low compression on #4 cylinder down to 50psi.All remaining cylinders have 150psi.Everyone is saying to replace powerhead.My questions are:

1 What can I check first before I make that decision changing out the powerhead.

2 Is there powerhead kits available to buy so I can rebuild the powerhead if needed

Thank you
Shane

 

[RCO]

You should pull the cylinder head and visually inspect the cylinder. You may get lucky and have only a bad head gasket, or you might have a broken ring etc. Rebuild parts are available, and is a reasonable DIY project it you are mechanically inclined. Only you can decide if it is worth the cost of parts, machine shop charges, and your time for a fresh powerhead, or roll the dice on a used one.

 

[jerryjerry05]

No kits that I know of??
The kit would probably have 5 pistons when you "MIGHT" only need 1 ??
The piston can be changed without a complete teardown.
Removing the exhaust chest would be hard and can cause more trouble than it's worth.
Some just replace the piston through the intake after the heads/ intake has been removed.

The #4 cyl runs one of the fuel pumps.(#1 is top)
Remove the pump and the port cover and look inside to see if there is any stuck rings or damage??

But first do what RCO suggested, pull the head and check the gasket.

 

[huck1545]

Thank you for your response.
Rco is there anywhere on here where I could find steps to take to remove cylinder head?

 

[jerryjerry05]

The head is held on with 22 5/16 bolts.
There are smaller ones there but they only hold the cylinder head cover on.
It's best not to try to take that off.

The bolts are fairly soft and can twist off easily.

You might need a torch and a can of penetrating oil and a hammer..

The threads usually come out easily, the area where the head contacts the mid section of the screw.
That area causes the most problems.
The dissimilar metals cause corrosion and they seize and can be REAL hard to undo.

I start spraying and heating and tapping the head of the bolts the week before(if possible).

Just go slow and take your time.

 

[huck1545]

Thank you jerryjerryo5 for your post.Would their be 24 5/16?Looks I have two that are just of to left side and looks like they mate to the block.

 

[jerryjerry05]

The parts diagrams all call for 22 but hey they could be wrong??
And I could be WAY wrong!!!!

 

[huck1545]

Well guys I removed my cylinder head it went smooth.Scoring is visible on the bore so she is done maybe a rebuild project overtime.I have two options that I can go within they are;

(1) marine shop has a force150 that they are willing to swap out power heads and controls plus test and Iam back on the water.

(2) 2003 Merc Optimax 150 with 25" leg up for sale.It has 650 hours and it's a saltwater version.My transom is a 20".My question to you guys is (A)Will a 25" leg work on my boat, (B) Will the mounting holes to the transom be the same, (C) Will their be a lot of changes regarding the controls.This motor comes with the controls.My boat is 1991 Campion Allante Classic 185 Cuddy Cabin.

Thank you
Shane

 

[jerryjerry05]

The 25" will be too long for your boat.

Some times you can make a 25" transom into a 20 but not the other way around.

Stick with the Force.

Also the change to Mercury will probably need cables, wiring and the transom redone.