Uping the horse power - Change a 75 into a 85?

[John-Mc]

Hi all.<br />I've a 1980 75HP Chrsyler. The local shop thats fixing my skeg has a bank of 3 carbs from a burnt out 1980 85 HP (no oil was in the gas...). Wants about $150 CDN for them.<br />From what I understand the 75 & 85 Hp engines are basicly the same, just different tuning. My question is - could I expect the performance of an 85 out of my 75 if I swapt the carbs over ? Are there other parts I would need to make the transformation complete ? Is there anything to watch out for when changing them over. I have had the originals off for a full cleaning and managed to reassemble & install them ok. I'd just like a little more grunt without spending bucks on another engine (and getting squat for the 75).<br />TIA,<br />John

 

[scotiany]

Re: Uping the horse power - Change a 75 into a 85?

I don't think so. More HP means more cubic inches. The carbs are single jet no matter what engine they're on. I do know the the 35-45-55 carbs are all very nearly identical.

 

[John-Mc]

Re: Uping the horse power - Change a 75 into a 85?

From what I can tell, both the 75 & 85 HP Chryslers are 72.39 cu inch engines.<br />I got that info from scans of factory brouchers located here: http://www.geocities.com/thechryslercrew/ <br />If displacement was a factor I know that just changing carbs wouldnt do it. I'm not terribly experienced with 2 strokers but I know there's not cam shafts and ohv's to complicate things.<br /><br />John

 

[The Marine Doctor]

Re: Uping the horse power - Change a 75 into a 85?

The 75 hp uses normal rings while the 85 uses pressure back rings. Changing the carbs will likely not benefit you too much.<br /><br />TMD

 

[John-Mc]

Re: Uping the horse power - Change a 75 into a 85?

Thanks TMD. Your guidance is appreciated. It sounded just too easy.<br />Is it possible to install those rings (or pistons) in the 75hp power head or is it different also ??<br /><br />TIA, John

 

[The Marine Doctor]

Re: Uping the horse power - Change a 75 into a 85?

I would have to check some numbers at work to see if the block is the same. If this is the case then you can probebly change into a 90hp.<br /><br />TMD

 

[jim dozier]

Re: Uping the horse power - Change a 75 into a 85?

Get a vernier caliper (the mechanic with the carb probably has one) and measure the venturi diameter of the carb on the 85 and on yours if its still off of the engine. They may be the same in which case its a mute point or they may be bigger (the 85). Chech before you buy.

 

[The Marine Doctor]

Re: Uping the horse power - Change a 75 into a 85?

I did some checking, compared the 75-85. They have different pistons. The block is also a different #.<br /><br />TMD

 

[John-Mc]

Re: Uping the horse power - Change a 75 into a 85?

Thanks TMD & all. I guess I'll have to live with what I have for now. Perhaps increasing my own performance by dropping a few lb's would help get me out of the water easier...<br />John