Distributor cap part number

[THenning]

So I looked up the engine serial on the store and ordered a replacement distributor cap for my 78 mercruiser 228. New one looks like it clamps on. Old one has holes. Pics attached. Help me with part #?

 

[Bt Doctur]

 

[Bt Doctur]

thats your box number but think what was contained within is incorrect

 

[THenning]

What's on the boat doesn't match what's in the box.

 

[achris]

What's on the boat doesn't match what's in the box.

We can see that... The new cap you have is the 'right' cap for that engine based on the year. Have you considered that the distributor in the engine may not be the original? Which appears to be the case.

The distributor on the engine looks like it might be (god forbid!) automotive. In which case you need to remove it and put a properly 'ignition protected' distributor in...

Chris......

 

[THenning]

Sticker on distributor: J1171 Marine, Distributor cap on boat says MERCRUISER STD. ROT. ENG.

 

[THenning]

[No message]

 

[achris]

Take the cap off and post a photo of the breaker plate (with the points in place)...

Chris.......

 

[achris]

So, a little digging has turned up a cap (2 actually) that may match what's on your engine. It's a cap from a Prestolite distributor.

Here's the rub... It's either a distributor from a 1987-1995 5.7 inboard (ski), cap part number 392-9766; or a distributor from a 1963 to 1969 327, cap part number 392-33708... Either way, it's not the right distributor (for a 1982 305 4bbl aka '228')...

And this...

...Distributor cap on boat says MERCRUISER STD. ROT. ENG.

That to me indicates that distributor could also carry a cap for reverse rotation, meaning, inboard.... If I was a betting man, I'd pick the 392-9766... But it's not my money....

Chris..........

 

[Scott Danforth]

looks like a prestolite dizzy

doesnt look automototive since there is no vac canister or the window for adjusting points that GM used

for a prestolite dizzy here you go

https://www.michiganmotorz.com/pres...html?gclid=CjwKCAjwvJvpBRAtEiwAjLuRPQaLUiHEvD 3NKg_iu-dYi1gjfqWUROFxpIEAsZTeiZOI5gKFtrXpjRoCNgwQAvD_BwE

https://www.amazon.com/Sierra-International-18-5352-Distributor-Cap/dp/B0002CADSK

prestolite dizzy with screw down cap for points type ignition.

MerCruiser part #392-9766Q1
Volvo Penta part #841070
Mallory part #9-29412

 

[THenning]

Thank you all so much! Have ordered the new parts. Here's to (Finally) being back on the water.

 

[THenning]

One more question, On the prestolite, how do I tell if my coil is internal or external resistor?

 

[THenning]

Update to this, I think this engine model used the old resistance wire. I suspect I'm overheating the coil. If I were to get an internal resistor, what wiring modifications would I have to make? Should I try the new coil and clean the contacts, keeping a resistance wire?

 

[Scott Danforth]

One more question, On the prestolite, how do I tell if my coil is internal or external resistor?

you have points. all points ignition have an external ballast on the run circuit (not on the crank circuit)