Help Identifying Force 90?

[BenV]

I purchased this boat several years ago, and am just recently starting to work on it. Finding parts has been like pulling teeth since I have no clue which year/model the engine is. Serial numbers are corroded right off (I made sure there were no grind marks from previous owner).

Also, any online source for some of the harder to find parts? Local merc dealers just aren't cutting it.

 

[Frank Acampora]

Re: Help Identifying Force 90?

Can't pinpoint it exactly but it is a late 1980s to very early 1990s Force--say in the area of 89-91.

If you drop the lower unit and it is a 2 piece drive shaft, it is a 90, if the drive shaft is 1 piece, it is an 89. To get the exact year and model, on the back of the engine block port side up high (above the spark plug line) you will see a stamped number. Take this to the dealer OR contact Mercury on line yourself and they can identify the engine. If not there, there may be a paper label (you can see it in photo #3) on the starter motor mount with a number like 906A90D (mine-1990 90hp). That is the model number.

Around the late 80s they went to the terminal board for ignition prior to that , it was quick-connect fittings.

If you can't find parts locally, contact Franz Marine at the Chrysler Crew website.

Parts are still available and your Merc dealer should be able to get into the Merc database to order parts.

And, believe it or not, almost everything is interchangeable with any three or four cylinder engine from 1980 t0 1990

 

[BenV]

Re: Help Identifying Force 90?

Well I didn't drop the lower unit because I have no clue how. So I got the two numbers that you directed me to, The model is 906X90B (Sticker on the starter), which I googled and came up with 1990 year. Thanks,

Now, Any suggestions on going about starting to work on this engine? The engine was apparently rebuilt 5 or so years ago, but since then it hasn't seen any love. Everything seems alright though, the engine itself runs, water pump works, although it loves to not stop when the key is in the off position.

 

[roscoe]

Re: Help Identifying Force 90?

Your best bet for perfect match parts is :

"www.mercruiserparts.com/selectDocs.asp?doc_nbr=FOB4494%2D1"

View the parts and make your selection, then take the part numbers to your local Merc dealer and place an order.

 

[roadrunnr]

Re: Help Identifying Force 90?

Ben:
you should probably start by getting a manual. Clymer is recommended for Force. This way you can follow the proceedure for removing the lower unit so you can replace the impeller. If your impeller is worn and not pumping enough water you could overheat the engine. You'll also want to make sure that the impeller housing isn't scored. Force engines are pretty touchy when it comes to running them too hot. Replacing the diaphram in the fuel pump is inexpensive and also a good idea as well as rebuilding the carbs. the proceedures for all of this can be found in a good manual along with wiring diagrams to troubleshoot your ignition switch problem

 

[Frank Acampora]

Re: Help Identifying Force 90?

The stop circuit is: White from CD boxes to engine terminal, connected to white in cable to dash, connected to one "M" terminal. Blue connected to other "M" terminal, to blue terminal on engine terminal board, jumped to ground.

When you turn off the switch, both "M" terminals have continuity and the CD boxes are shorted to ground through the blue wire. If the engine does not stop when the key is turned off, either the switch is bad or one of the blue or white wires are not connected somewhere.

Until you find the problem, if you want to stop the engine, just jump white terminal on the engine to either blue or ground.

Looking at your photos, I see a lot of corrosion on both the head bolts and the exhaust chest cover bolts. ---Guaranteed to give you trouble if you try to remove them. If the engine runs well, do not be tempted to disassemble unless absolutely necessary.

Oh! BTW: In the fourth photo you can see two relays bolted to the bottom pan on the port side. These are the tilt/trim relays. They are standard and can be bought new at electrical supply houses and can be found in Chevy and Buick in the junkyard. If your tilt stops working, replace both of them. Since they are default to ground, either could be bad and are sometimes difficult to pinpoint which one. So just replace both--saves headaches.

And when you do go to drop the lower unit, there is a seventh bolt hidden inside the exhaust snout--you need to remove the exhaust snout the get to it. And remember to disconnect the shift linkage connector in the front of the lower unit--A very small cotter pin and headed pin hold it together. See the sticky at the top of this forum--your 90 will be basically the same with the exception of the pump itself and the two piece drive shaft.

Hint-Hint--- You will see one small black ground wire from CD box and coil mounting plate to the block. To forestall ignition problems due to poor grounding, Daisy Chain a separate ground from each coil and CD box to the ground terminal on the other side of the engine. That will give a good corrosion free ground right through to the battery.

Did you remove the airbox? there should be a silencer/ air box with three gaskets in front of the three carbs, held on with six screws. Its primary function is to contain and recycle spit-back from the carbs. This liquid is recycled from a hose on the bottom of the airbox through a metered nipple on the bottom of the manifold--port side.

 

[BenV]

Re: Help Identifying Force 90?

Your best bet for perfect match parts is :

"www.mercruiserparts.com/selectDocs.asp?doc_nbr=FOB4494%2D1"

View the parts and make your selection, then take the part numbers to your local Merc dealer and place an order.

Recently I've been going to one local shop (Sherwood Marine) to be getting part numbers, then they forward me down the street to another local joint (Alpine Marine) and i've been successfully getting parts. But the time it takes is just painful. This is my third week waiting for a single bolt so I can put the airbox on.

---

I purchased a Clymer manual a week ago luckily, it seems to cover just about everything I need. I just wish it didn't cover ALL force engines from 4-150hp, 1984-1999.

---

I'm going to go investigate the engine not stopping now, Up to now, I've been using the choke just to kill it, But I'd like to keep it proper. As for the lower unit/impeller, I dont have the resources to work on that part right now. Would I be alright just leaving it for now as it pumps water just fine as far as I can tell?

 

[Frank Acampora]

Re: Help Identifying Force 90?

Oh, man! don't wait for screws--they're all standard hardware. And anyway, the screws for the airbox are a pain to get to the bottom two. I always replace them with stainless Allen head with a washer underneath. (standard 1/4 X 20 thread--whatever length) Available at any Lowes or Home depot--specialty screw and hardware. Even the stock pan head screw may be available there.

When you do replace the airbox, be careful with the gaskets, They are very close to the choke stop arms and if you get them in a little crooked, they will stop the chokes from closing.

Instructions in Clymer are reasonable for most repairs. You don't need any special tools to drop the lower unit. If it is pumping a good amount of water, and the engine is not overheating there is no pressing need to replace the impeller---Just be aware that impellers do wear, get hard, and break vanes with age. They are a normal maintenance part and you do not know the condition of the one in the engine now. Be sure your overheat indicator is working properly. If it goes off, stop the engine. 17 bucks for a new impeller is cheap insurance against overheating an engine and scoring cylinder walls at multiple hundreds of dollars repair. Also, replacing the lower unit oil is a good idea--costs only a couple of bucks and will give you a good idea of the lower unit internal condition.

Also, in looking back at your photos, I advise you to be very careful--the neutral interlock switch has been bypassed and your engine is capable of starting in gear. As a matter of fact, your engine can be started at full throttle position as it is now. (brown rectangular microswitch with white button just above shift linkage) Very dangerous at the dock if engine starts in gear. You will see the two yellow wires have been removed from the interlock switch and spliced together. SO: this tells me that the previous owner had trouble with idle speed and starting the engine, and didn't know what to do about it (most likely) or the switch is broken. When you get your Clymers, re-hook the neutral interlock switch and then follow the directions for synchronizing throttle and shift. Check to see if your switch is ok. There should be no continuity (open switch) with the button out. The switch should be closed with the button depressed.

 

[BenV]

Re: Help Identifying Force 90?

They should be here by next week, so i'm not really putting a rush on that part. I'll keep that tip in mind though if they backorder for any longer than that.

--

I started it up today to test some electrical work I did envolving some lights, and it seemed to be pumping water quite happily. Much better than when I first flushed the engine (salt buildup?). I also rewired the overheat alarm because I found it rolling around in the bilge of all places (Previous owner was the worst electrician I have ever seen.) I was going to replace the lower unit oil sometime soon, anywhere you can point me to starting on that, since I've never done it before.

And about that switch, when I recieved the boat, it was cracked all the way through with the wires disconnected, since then I've replaced the part but haven't replaced the wiring.

 

[Frank Acampora]

Re: Help Identifying Force 90?

Yeah! Overheat alarm should be under the dash where the driver can hear it if it goes off. One wire from the buzzer connects to the "I" terminal of the ignition switch, other wire connects to the orange wire in the cable. Circuit is: Overheat switch on engine goes to ground when hot. Voltage then flows froM "I" through buzzer through orange wire to ground. "I" is switched terminal so when you turn off engine, the alarm is silenced --so it doesn't annoy the hell out of you-- until the engine is cool enough to start.

"I" terminal is used for 12 volt power for anything you want on only when the engine is running--like gauges.