90 hp Force outboard won't rev past 1500

[jms_mt]

This is probably a simple fix but it has us stumped. We have a 1990 90hp Force Outboard. Last week, first trip of the year, it accelerated and ran well for about 100 yards, then lost the waterpump impeller and impeller housing, the motor shut down and wouldn't run. Installed a water pump kit, motor will now start, is pumping water but it won't rev over 1500rpm. It's firing on all 3 cylinders, but just has no power. Is there a safety mechanism on this unit for a case when the water pump malfunctions which would cause the timing and acceleration to be affected? Managed to get it to run in reverse out of marina, but while shifting into neutral and then into forward, the motor dies everytime. Able to manually advance timing and throttle in neutral to 4500rpm but the motor dies when trying to use controls.

 

[roscoe]

Re: 90 hp Force outboard won't rev past 1500

Do a compression check. My guess is that you blew a head gasket or maybe warped the head when it overheated, which is causing the low compression and the lack of power and stalling.

 

[jms_mt]

Re: 90 hp Force outboard won't rev past 1500

thanks for the suggestion, we will check the compression...but there's another twist here. If we manually advance the timing and throttle, it seems to accelerate just fine (with poor compression, in theory, that wouldn't occur) It also seems to run just fine in reverse but dies when shifting to neutral and forward. When a water pump loses the impeller & the engine heats, is there some type of safety mechanism that retards the timing?

 

[sony2001]

Re: 90 hp Force outboard won't rev past 1500

No safety mechanism for timing. Idle speed should be high enough (900) to go into gear and not stall. Bolt at bottom of vertical shaft for carbs, left of carbs. Try (1000). If stalls you have another problem. If engages well then look at the contol cable function. The problem should be there.

 

[mantis80]

Re: 90 hp Force outboard won't rev past 1500

Compression still could be an issue due to load. I have had similar issues recently thinking that the problem was with fouled plugs or ignition problem when it is really compression loss on my third cylinder. Also check the neutral safety switch of the remote unit. I don't suggest bypassing BUT, you could do so to verify if that is causing it to stall.

 

[jms_mt]

Re: 90 hp Force outboard won't rev past 1500

We think we're on our way to getting this figured out. Today we adjusted the shifting linkage plates to make sure they were lining up "flat in neutral", and clearing correctly when in forward or reverse. Havn't put it back in the water yet to see if this adjustment worked. Cables were sound and we didn't have to move lock nut to adjust the shaft. (When we put the lower unit back on after installing the water pump, we apparently moved the location of the shaft when reconnecting to the upper unit with the pin) We have a bigger problem to deal with--Checked compression. 120 top and bottom cylinder but middle cylinder is only putting out 60 pounds...<br />Havn't pulled the head yet to check for warp in the head or cylinder damage. Any suggestions for replacement pistons? We're assuming we should have the head checked and machined if necessary and that all 3 cylinders should be honed and new pistons and rings installed. With all of these things going on, I ordered the shop manual today for this engine. Thank you for your help and suggestions.<br />I think we have a snowball starting to roll.