12 ft lonestar 9.5 johnson

[Dad85]

I have a question about motor size on a 12ft lonestar boat it has a 1972 johnson 9.5 on it and just wondering what kind of mph I could expect and should it plane with 1 person in it because it seems it is only running about 5 miles per hour and does not plane at all not sure what rpm it is running at wot but doesnt sound like its is running all that fast I can't upload a picture but it is a semi v but most of the boat is flat is it the prop it has a 8.25x8.5

 

[racerone]

Should plane out easily.----My bet is that it is running on 1 cylinder.-----Does spark jump a gap of 1/4" on both leads , yes or no ?------

 

[Dad85]

Should plane out easily.----My bet is that it is running on 1 cylinder.-----Does spark jump a gap of 1/4" on both leads , yes or no ?------

I will have to check tomorrow I do know that it does low rpms in a trash can on 2 cylinders because I pulled one plug wire off at a time and the engine died down on each one also both the plugs are clean

 

[DeepCMark58A]

I coil goes bad pretty common, easy to find online, reasonably priced too.

 

[racerone]

Coils are cheaper today then they were 50 years ago.

 

[DeepCMark58A]

Coils are cheaper today then they were 50 years ago.

Might as well buy two for trouble free boating.

 

[Scott06]

you can ohm test the coil before you replace. Would also look if plugs look like they are running lean from dirty carb

Would also agree that it should plane easily. Check for spark Has a similar situation with neighbors 70 hp merc a few years back plug wire from coil to plug was bad had one dead cylinder

for reference had a 12 ft tinny growing up with a 5.5 Evinrude planed easily with two people. Was no speed demon. Boat was rated for 7.5 hp, occasionally I had taken my grandfathers 9.5 Evinrude kicker (I think same engine as yours) and put it on it then it was pretty spirited, so you should be going ok.

 

[racerone]

Check fuel pump diaphragm.---Check for broken front mount , pulls choke on at full throttle.--Check reed valves.----Post actual compression values here.----Install a new water pump impeller.----Check thermostat as they are often stuck open or missing.

 

[Texasmark]

That boat and engine should approach 30 with the right prop......but a prop change won't fix your current situation.

 

[Dad85]

Check fuel pump diaphragm.---Check for broken front mount , pulls choke on at full throttle.--Check reed valves.----Post actual compression values here.----Install a new water pump impeller.----Check thermostat as they are often stuck open or missing.

I will check the other things but compression was 70 in 1 80 in 2

 

[Dad85]

Might as well buy two for trouble free boating.

That surprised me when I saw 18 bucks a piece for oem

 

[Dad85]

Might as well buy two for trouble free boating.

I would most defenantly just replace both if are bad

 

[Dad85]

That boat and engine should approach 30 with the right prop......but a prop change won't fix your current situation.

That is definitely good to here because I also spun the hub last time but I know that is not my engine not reving issue

 

[Dad85]

Should plane out easily.----My bet is that it is running on 1 cylinder.-----Does spark jump a gap of 1/4" on both leads , yes or no ?------

Yes spark on top jumps about 3/8 spark on bottom 1/2 to 5/8 all while spinning motor with drill

 

[Dad85]

Update thermostate is missing coil arc on top will jump a 3/8 gap bottom is like a 5/8 gap plugs have a bit of oil on them but they are brand new points gap is set at .20

 

[Dad85]

And I forgot compression is 70 and 80

 

[Texasmark]

I will check the other things but compression was 70 in 1 80 in 2

Sounds like time for an engine overhaul. You should be up around 120 PSI for rated performance.

 

[cyclops222]

should have thermostat and any other parts if it needs them.

 

[DeepCMark58A]

Or try soaking the cylinder in tranny fluid while you are waiting for parts.