90 hp force suddenly died on water and won't start

[raiderzfan422]

I am new to working on 2stroke outboards but tried some basic diagnoses so far. Motor cut off at WOT on the lake and I got towed to dock. Motor would barely crank over when I tried to restart. Took out battery charged over night and next day installed. Motor cranked over normal and even started and ran for 5 secs then died. Tried to restart and cranked very slow again. I thought maybe bad battery or starter so I purchased new battery and took apart starter. Starter was in need of rebuild so I did that also. Same problem it would start within the first few attempts then die 5 secs later and hard cranking again. Compression tested and all 3 were good and also checked for spark and was good there also. Tried spraying fuel mix in as I cranked and no go either. I then pulled all spark plugs out and cranked it and it still cranked slower then it should?? This is where I am at now. Lower unit was rebuilt last fall and ran fine before I winterized it. The motor problem happened about 45 mins my first time out this summer. Can't figure out why if I wait a day it will crank great then after a few tries slow crank. Next day same thing crank fast then slow again. Also noticed the prop was slowly spinning as I was cranking but read that is normal?? Also I removed all battery cables and grounds and wire brushed them clean

 

[foodfisher]

Re: 90 hp force suddenly died on water and won't start

My approach--Battery: even new could be weak=load test. Slow spinning prop=normal. Initial cut off at WOT=possible electrical, check around flywheel for rubbed bare wire, wiggle all connections to try and feel for a break inside the insulation. Possible fuel= check the fuel pump diaphram.

 

[jerryjerry05]

Re: 90 hp force suddenly died on water and won't start

Year? Model? Serial#?
What are the comp#s?
Maybe it's overheating? Test the temp sender and the buzzer?
Drain the lower and check the oil?Sometimes a bearing can sieze and make it hard to turn over?
Check the timing?
Check the fuel pump diaphram?
Sounds like you have a couple of prolems???

 

[Jiggz]

Re: 90 hp force suddenly died on water and won't start

Well if it is still cranking slow with plugs out most likely there is problem with the LU. Drop the LU and then try spinning the flywheel by hand with the plugs out it should spin freely. If not then the problem is in the power head. If it spins, investigate the LU. With the LU dismounted and in neutral you should be able to spin the drive shaft by hand although a little heavy initially.

 

[raiderzfan422]

Re: 90 hp force suddenly died on water and won't start

It's a 1990 90 hp force 906x90a. Where about is the fuel pump diaphram and what problem with that would I be looking for? I know temp sensor works. I am gonna have to get the boat from my dock to launch and drop lower unit. I believe compression was 130 on all 3 I do know they were all within 1 or 2 of each other. I won't be too happy if my fresh rebuild of my LU last fall is leaking water as that was problem when I took it in.

 

[foodfisher]

Re: 90 hp force suddenly died on water and won't start

Fuel line from the tank leads to the pump. Screws release the cover. The piece of rubber exposed is the diaphram. If it is stretched into a bag, slits, or pinholes=replace.