Johnson seahorse 5hp and7.5hp

[superspark]

Hi all, I have a 7.5 Seahorse model J8BALCSS(1980). I have replaced quite a few parts but it is an unreliable starter with a weak spark.
A friend gave me a 5 hp Seahorse model number BJ5BFLCDE which is siezed and as the gear change wont move I assume the it
is the gearbox which is the problem. I have thought of taking the lower unit from the 5 and replacing it with the unit from the 7.5.
In looking through various parts catalogues to check compatability, I can't find any reference to a 5hp being made in 1986.
Can anybody help please?
regards
George

 

[mekkamaz]

Re: Johnson seahorse 5hp and7.5hp

Hello, Sorry to hear you give up on your 7.5. I have had one for 20+ yrs and the only things needed to be changed was fuel and water pump!! So maybe if you change a lot of parts, you can be close to a solution maybe faster than trying to make 1 out of 2....but if you still want to change gearcases, it is a simply task to do to remove them and compare one to each other in site, this is the best reference to swap. If you want to try some other options for your 7.5, I?ll be glad to help trying to do the last chance, as I?m very fond of this little motors....good luck!!

 

[1946Zephyr]

Re: Johnson seahorse 5hp and7.5hp

The shifter being stuck on the 5hp, may be just the shifter itself. It's nothing uncommon for corrosion to sieze these up. Check the oil in it and see what comes out. You may just have to remove the shifter shaft and clean and re-lube it,

As far as your 7.5 goes, what exactly have you replaced?

 

[superspark]

Re: Johnson seahorse 5hp and7.5hp

Hi mekkamaz, good of you to reply so fast.
I gave up on the 7.5hp 10 years ago when on a short journey (300 yds) it got so hot as to melt all the throttle cable and plastic thermostat cover etc. At the time, water was pouring out of the engine as it always did and cold. As i'm a delivery Skipper I have not used my own boat since then. Now I have given up the business so will be sailing my own little yacht hence the repair. I have stripped the head and cleaned out the water jackets but they were not blocked. Renewed the impellor though it seemed ok. Fitted a new throttle cable and of course all relevent gaskets. The engine did start in the test bin and ran cool. the second time i tried, it wouldn't start after 1 hr of trying and breaking the recoil starter so I gave up, then I was given the 5hp but as I say, It is siezed up. It is a shame because the 7.5 was used for 20yrs on my boat and was always reliable.
regard
George

 

[superspark]

Re: Johnson seahorse 5hp and7.5hp

Hi 1946Zephyr Thanks for your reply. If you look at my reply to mekkamaz, it explains the circumstances. The engine wont turn over so I have assumed the gearbox is siezed as is the gear change lever. I can get a slight (very slight) movement out of it and can hear the pistons moving when I listen through the plug hole. Any help you can give would be greatfully appreciated.
Regards
George

 

[mekkamaz]

Re: Johnson seahorse 5hp and7.5hp

It is very good practice on this 20+ motors to change the whole water pump, as plates worn out and even you put new impeller, does not push enough water. And upstream, a new thermostat is not an expensive fix, all togheter will assure propper cooling. And if you remove the head gasket, an clean all passages, that shoul do it. As your hard start I think you can perform a couple of spark test that should tell if there?s spark or fuel issue.

As Captain Zephyr says, please do tell us what more have u change of the 7.5, maybe we can wake it up!! Cheers!!

 

[superspark]

Re: Johnson seahorse 5hp and7.5hp

Thanks again mekkamaz. I will have time this week to work on the engine so will let you know
how I get on. I didn't know it had a fuel pump but now realize it must have as it hasn't got an
overhead tank. Thanks for that,