1977 35 hp Johnson water intake revision on gear case

[heypawpaw]

Have a new to me J35EL77H. Picked up a new water pump kit 389890 today and paperwork in box explains how to drill two 5/32" on each side of gear case above intake screens below ventilation plate. Also says to measure two holes on forward edge of exhaust of housing and if 13/32" remove lower mount and drill holes to 5/8". Are these changes necessary?

 

[F_R]

I'm not familiar with the specific mod, but the two holes behind the mount are drain holes for the drive shaft enclosure tube. They must think the existing ones do not provide enough drainage. If it doesn't drain fast enough, there is danger of the water rising in the tube enough to cause damage to the powerhead. So, if they say to enlarge them, I would assume there has been a problem.

The other two--as said, I'm not familiar with them.

 

[jimmbo]

First I ever heard of them

 

[heypawpaw]

Thanks F_R just exploring options before drilling. It's an updated BRP fuel pump kit plastic with stainless liner and thicker but smaller diameter impeller. Mods say use short straight edge along leading and trailing edge of intake holes and mark where straight edge meets curved radius below cavitation plate. Center punch then drill two holes 5/32" at 45 degree upward angle. Accuracy important as drilling too far aft may enter oil passage rather than water passage.

 

[F_R]

All I can say is do it as they say, or leave it alone. I don't know the consequences of leaving it alone with the updated pump.

 

[heypawpaw]

Thanks F_R. While digging around online, found BRP 5008496__2001 Service Update Book Says on 15 to 30 hp when using muffs to cover auxiliary intake holes below cavitation plate so water doesn't leak out. Just went to hardware store for drill bits and will do as BRP says and drill two holes on each side of gear case and drill exhaust housing holes to 5/8".

 

[Willyclay]

Picked up a new water pump kit 389890 today...

Part number you listed is for an "Extension Kit" which is NLA. Believe the correct part number for your motor is 389980. I am following your thread because the mods may also apply to my 1985 Johnson 25. Good luck!

 

[racerone]

A 1985 model 25 hp has totally different water intake set-up.---Does not need modification like the 77 models.

 

[heypawpaw]

Yes Willyclay 389980 is the correct number I typed it wrong and your engine is not affected. Looking at parts diagrams Your 1985 was first year 25 hp updated the pin drive split gearcase to the through hub gearcase with water intake located near center of gearcase. On 35 hp from 1976 through 1979 water intake is near leading edge of gearcase. In 1976 and 1977 35hp used water pump kit# 388256 that included pump housing 322260 and in 1978 starts using pump housing 390159 which is included in kit# 389980. In 1980 35 hp gearcases changed location of water intake to near center of gearcase.

 

[oldboat1]

I read through the instruction sheet for kit number 389980 for model 35EL77H (technical info. included in the parts listing for the kit at a competing site.) The extra hole in the leg at the engine mount is baffling to me (maybe F_R's explanation applies). Maybe the smaller holes under the AV plate are for additional venting to improve pump operation.

Think I would try it without all that drilling and see how it runs with the new impeller and kit. I know it's bad practice to second guess engineers, but if it pumps well and the head temps are normal....

 

[heypawpaw]

Well..... I went ahead and drilled the auxiliary intake holes before installing the new water pump. The holes on the forward edge of the exhaust housing measured just over 1/2" so I won't drill those.

 

[oldboat1]

sounds like a decent approach -- would like to hear how it works when you get it up and running.

 

[Willyclay]

Great info, thanks!

 

[heypawpaw]

Test ran motor in a drum and strong stream from weep hole and spray from rear exhaust holes. Let motor run for nearly half hour starting and stopping while checking it over adding water as needed and pump worked great but starter bendix spring sometimes remains collapsed under upper spacer allowing starter gear to vibrate and rise when raising rpms so it appears a new spring nut and spacer are the next project.